Carbonate rocks: Physical and Chemical Aspects (Developments in Sedimentology 9B)

DEVELOPI\-iENTS IN SEl)IMENTOLOGY 9B DEVELOPMENTS IN SEDIMENTOLOGY 9B CARBONATE ROCKS Physical and Chemical Aspects ...

Author: George V. Chilingar | Harold J. Bissell | Rhodes W. Fairbridge

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DEVELOPI\-iENTS IN SEl)IMENTOLOGY

9B

DEVELOPMENTS IN SEDIMENTOLOGY 9B

CARBONATE ROCKS Physical and Chemical Aspects

EDITED BY

GEORGE V. CHILINGAR Professor of Petroleum Engineering University of Southern California, Los Angeles, Calif. (U.S.A.)

HAROLD J. BISSELL Professor of Geology Brigham Young University, Provo, Utah (U.S.A.) AND

RHODES W. FAIRBRIDGE Professor of Geology Columbia University, New York, N.Y. (U.S.A.)

ELSEVIER PUBLISHING COMPANY Amsterdam London New York 1967

ELSEVIER PUBLISHING COMPANY

335 JAN VAN

GALENSTRAAT, P.O. BOX

21 1, AMSTERDAM

AMERICAN ELSEVIER PUBLISHING COMPANY, INC.

52 VANDERBILT AVENUE, NEW YORK, N.Y. 10017

ELSEVIER PUBLISHING COMPANY LIMITED RIPPLESIDE COMMERCIAL ESTATE, BARKING, ESSEX

LIBRARY OF CONGRESS CARD NUMBER

WITH

65-20140

80 ILLUSTRATIONS AND 70 TABLES

ALL RIGHTS RESERVED THIS BOOK OR ANY PART THEREOF MAY NOT BE REPRODUCED IN ANY FORM; INCLUDING PHOTOSTATIC OR MICROFILM FORM, WITHOUT THE WRITTEN PERMISSION FROM THE PUBLISHERS PRINTED IN THE NETHERLANDS

CONTENTS

CHAPTER 1. INTRODUCTION R. W. FAIRBRIDGE (New York, N.Y., U.S.A.), G. V. CHtLINGAR (Los Angeles, Calif., U.S.A.) and H. J. BISSELL (Provo, Utah, U.S.A.) . . . . . . . . . . . . . . . . . . CHAPTER 2. ELEMENTAL COMPOSITION OF CARBONATE SKELETONS, MINERALS, AND SEDIMENTS K. H. WoLF (Canberra, A.C.T., Australia), G. V. CmuNGAR (Los Angeles, Calif., U.S.A.) and F. W. BEALES (Toronto, Ont., Canada) . . . . . . . . . . . . . . . . . . CHAPTER 3. PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES W. H. TAFT {Tampa, Fla., U.S.A.) . . . . . . . . . . . . . CHAPTER 4. CHEMISTRY OF DOLOMITE FORMATION K. J. Hsu (Riverside, Calif., U.S.A.) . . . . . . . . . . . .

23

. .

151

. . . . . .

169

CHAPTER 5. STABLE ISOTOPE DISTRIBUTION IN CARBONATES E. T. DEGENS (Woods Hole, Mass., U.S.A.) . .

193

CHAPTER 6. INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES 209 B. L. MAMET (Bruxelles, Belgium) and M. o'ALBISSIN (Paris, France) . . . CHAPTER 7. THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

J. M. HUNT (Woods Hole, Mass., U.S.A.) . . . . . . . . . . . . . . . .

225

CHAPTER 8. TECHNIQUES OF EXAMINING AND ANALYZING CARBONATE SKELETONS, MINERALS, AND ROCKS . K. H. WOLF (Canberra, A.C.T., Australia), A. J. EASTON (London, Great Britain) and S. WARNE (Newcastle, N.S.W., Australia) . . . . . . . . . . . . . . . . . . • • . 253 CHAPTER 9. PROPERTIES AND USES OF THE CARBONATES F. R. SIEGEL (Washington, D.C., U.S.A.)

343

REFERENCES INDEX

395

SUBJECT INDEX . . .

404

Chapter 1

INTRODUCTION RHODES W. FAIRBRIDGE, GEORGE V. CHlLlNGAR AND HAROLD J. BISSELL

Columbia University, New York, N. Y. (U.S.A.) University of Southern California, Los Angeles, Calif. (U.S.A.) Brigham Young University, Provo, Utah (U.S.A.)

Carbonates constitute some 10-15 % of the sedimentary rocks of the earth’s crustl, as well as contributing to some important igneous and metamorphic rock types. Thus high- and low-temperature carbonate types are recognized, but in this book the authors are considering almost exclusively the latter. Field and laboratory investigations of ancient sedimentary carbonate rocks must of necessity be extended beyond the realm of origin and classification only, and should take into consideration the physical and chemical properties of these sediments. In order for these studies to be scientific and meaningful, careful research of such properties of modern carbonate sediments must be undertaken on a scale ranging from world-wide field investigations to all those detailed laboratory techniques now known to sedimentary petrologists and petrographers. Realizing that the bulk of ancient sedimentary carbonate rocks accumulated in various depocenters of the marine realm, researchers have directed most of their attention to this environment in an effort to learn more of the physical processes of desiccation, compaction, expulsion of interstitial water, congelation, pressure-cohesion, grain orientation, and others. Furthermore, serious study is also being made of sedimentary structures which heretofore were thought to be present only in sandstones; included among these sedimentary structures are various types of crossbedding, ripple-marks, mud-cracks, bottom markings, slump structures, rippledrift lamination, and many more. Certain coarse carbonate deposits have been identified as turbidites, and theories have been advanced to account for their mode(s) of origin. All in all, geologists desire to know the entire spectrum of processes, physical, chemical, biologic, and their combinations, which lead to ultimate lithification of carbonate sediments. Factors involved include compaction, pore reduction, expulsion of interstitial fluids and gases, pressure-cohesion, cementation, crystallization and recrystallization, dolomitization, silicification, bacterial effects, and introduction of authigenic or metasomatic substances such as iron, sulfates, and Some estimates run as high as 25% by volume (CHILINGAR, 1956d). All calculations must be revised, however, in the light of drilling beneath the oceans. At the present time none of the 10%. estimates is likely to be correct by

+

2

R. W. FAIRBRIDGE, G. V. CHILINGAR A N D H. J. BISSELL

phosphates. Lime-muds of modern repositories contain as much as 80% water, suggesting that ancient lime-muds had comparable water contents; when these sediments dehydrate they become denser and resultant shrinkage is taken up by physical compaction of the sediments. (1959, p.298), several firmly settled, modern calcareous According to WELLER sands have been observed to have porosity between 50 and 60% (or more), which is higher than that of quartz sand (37%). Not many limestones, however, retain more than 10% porosity; numerous limestones practically are non-porous. According to recent research by ATWATER (1965) on sandstones, burial to 30,000 ft. results in a reduction of porosity to 2.5% (largely through intergranular pressure solution); the almost total loss of porosity in medium- to fine-grained limestones under similar burial may well be predicted. Inasmuch as empty shells and porous structures are not crushed in many coarse-grained carbonate rocks, consolidation was probably accomplished at an early stage before being subjected to much overburden pressure (WELLER,1959, p.298). The time and conditions of consolidation of many limestones by cementation are uncertain. The question of whether the calcareous muds compact less readily than clay or not still remains to be answered. The weight of overlying sediments, however, is obviously an important factor in compaction. High-pressure (up to 200,000 p.s.i.) compaction studies were conducted by RIEKEet al. (1964) on the hectorite clay from Hector, California, containing 50-58% by weight of CaC03. The remaining moisture content versus the logarithm of pressure curve was similar to those of pure clays. No significant changes in the X-ray pattern have been noticed by these writers. The chemical composition of modern sea water is approximately the same over the very large expanse of the oceans; in the littoral zone, however, and particularly near the mouths of rivers, there is dilution of the ocean water by fresh water. The dissolved solids in ocean waters (volume = 1.37 * lo9 km3; specific gravity = 1.05) amount to 5 1016 metric tons, assuming an average salinity of 35%,, (SVERDRUP et al., 1952, p.219). The composition of sea water is presented in Table I. In addition to the ions listed, there are over 36 others elements present. Material contained in sea water is chiefly in ionic form. Only a small part of total solids occurs as colloids in different degrees of dispersion, these being chiefly clay particles and some organic matter. Various organisms are present, and ocean water contains atmospheric gases in varying amounts depending on depth and the history of the water mass. It must also be realized that the form of some of the elements in sea water is far from being known, and various changes of local or regional significance, such as the COz content, influence ionic equilibrium. As shown in Fig.1, the order of increasing solubility of various chemical compounds of sedimentary deposits is as follows: Al, Fe, Mn, SiOz, Pz05, CaC03, CaS04, NaCl, MgC12. The solubility depends on the following physicochemical factors: (I) pH; (2) Eh; (3) COz content; ( 4 ) chemical composition of solution; (5) size of dissolved particles; (6) temperature; and (7) pressure. It is obvious, therefore, that any at-

3

INTRODUCTION

TABLE I (CHIEFCOMPONENTS)~

CHEMICAL COMPOSITION OF SEA WATER

Ion

Percentage of dissolved solids

mg/kg*

Percentage equiv.

Na+

30.62 (S)

10,707 (A) 387 (A) 1,317 (A) 449 (A) 19,343 (A)

38.50 (A) 0.82 (A) 8.95 (A) 1.73 (A) 45.10 (A)

2,688 (A) 13 (s) 4.7 (S)

4.63 (A)

K+

1.10 (S)

3.69 (S)

Mg2+ Caa+ CIBrHCO3Co&

1.15 (S) 55.04 (S)

0.41 (S)

sod2-

7.68 (S)

Sr2+ B3+ Sr2+, H3B03, Br'A

=

0.31 (S)

After ALEKIN(1953, p.269); S

*See also Appendix A.

=

After SVERDRUP et al. (1952, pp.214, 220).

tempt at understanding physical and chemical aspects of present-day marine sediments must take into account these variables; however, the extrapolation of the data so gained to interpret the origin of ancient sediments has inherent hazards. Still, with the full realization of all these uncertainties, tremendous and significant advances are being made. For example, a research program into some / A

J

ii

/

1.000

/

A

/

/ "/ / /

- 0

/b

O

.o 0' d

Fig.1. Solubility(mg/l) ofvariouschemicalcomponents of sedimentary rocks in water at atmospheric pressure. (After RUKHIN,1961, p.275, fig.10-IX.)

4

R. W.

FAIRBRIDGE, G.

V. CHILINGAR AND H. J. BISSELL

of the aspects of mineralogy and chemistry of modern, unconsolidated carbonate sediments of southern Florida, the Bahama Islands region, and Espiritu Santo Island (by TAFTand HARBAUGH, 1964) was undertaken to understand better the relationships of different carbonate minerals in different sedimentary environments. One significant result of the study was the lack of evidence to suggest that either aragonite or high-magnesium calcite is being transformed to low-magnesium calcite within the unconsolidated sediments which were investigated. It was suggested by these workers that inversion or transformation are not taking place because the concentration of magnesium ions in the water surrounding the mineral grains in the sediment is high. The high concentration of magnesium ions in interstitial water apparently prevents transformation of aragonite and high-magnesium calciie. The role of the various trace elements, notably Mg, Sr, Mn, Pb, etc., in controlling the precipitation and stability of the metastable carbonates, especially aragonite and high-magnesium calcite, has received considerable attention in recent years. GOTO(1961) has shown that the solvation effect of the water molecules is critical in loosening the atomic bonds of carbonate minerals of distinct structural densities, and is hindered at elevated temperatures. Experimental work has shown that the crystal form is closely controlled by the ionic concentrations. SANDERS and CRICKMAY (1945, pp.25 1-253) discussed the chemical character of Quaternary and Tertiary limestones of Lau, Fiji, in &e Southwest Pacific. Particular emphasis was placed on investigating dolomite content. They observed that dolomitization seems to be unrelated to the fossils present. Coral rocks are generally no more dolomitized than algal rocks; but, in any particular dolomitic rock, dolomite is most abundant in corals and least abundant in Algae and echinoids. Furthermore, replacement by dolomite appears to be roughly dependent on solubility of skeletal remains, being most common in the easily soluble aragonite shells. It was also noted that dolomitization is related to original texture: permeable reef rock and calcarenites are usually the most strongly dolomitized. These two examples are mentioned for the single purpose of calling attention to the benefits of field-oriented research into physical and chemical aspects of modern sedimentary carbonate materials, but can equally well apply to all carbonates ranging from those forming today to those as old as Precambrian. Such work must involve careful studies of elemental composition of marine organisms as well as those of the sediments themselves. As pointed out by VINOGRADOV (1953, p.16), . the fate of some chemical elements . . . is connected with their accumulation in the sediments so that much clarification is still needed in regard to the study of the elemental composition of marine organisms which extract a large number of elements from the sea and concentrate them a hundredfold or a thousandfold in the sediments, silts, and so forth." The monumental study by VINOGRADOV (1953) has contributed substantially to our knowledge of the geochemistry of the sea. For the better understanding of physical chemistry of dolomite formation, two figures may be consulted. Fig.2 shows the region of dolomite formation in

". .

5

INTRODUCTION

Fig.2. Region of dolomite formation in saturated chloride and sulfate solutions. (After VALYASHKO, 1962, p.57, fig.14.)

Fig.3. Solubility of CaC03-MgC03-HzO system at Pco,=l atm. and Pc0~-0.0012 atm. and temperatures ranging from 0" to 70°C. Points between ordinate and 45 "-line represent solubility of calcite-dolomite mixtures, whereas those between 45"-line and the abscissa represent dolomitemagnesite mixtures. The amounts of Mg(HC03)z and Ca(HC03)z are expressed in mmole/l ,OOOg solution. (After YANAT'EVA, 1950, 1954; also see CHILINGAR, 1956a; BARONand FAVRE, 1958.)

-

saturated chloride and sulfate solutions, and Fig.3 indicates the solubility of the CaC03-MgC03-HzO system atpcoz 1 atm. and temperatures ranging from 0 to 70°C. In Fig.3, the points of intersection between the bisectrix and dolomite saturation curves show the composition of solutions saturated with respect to pure dolomite, whereas the solubilities of pure CaC03 and MgC03 are shown on the ordinate and abscissa, respectively. On the other hand, the solubilities of mixtures of dolomite calcite and dolomite magnesite (two-phase) are shown by the junction (nodal) points. The curve connecting these junction points to the left of bisectrix represents solubility of mixtures of dolomite and calcite, whereas the one

+

+

6

R. W.

FAIRBRIDGE, G.

V. CHILINGAR AND H. J. BISSELL

at the right of bisectrix represents mixtures of dolomite and magnesite. In all cases, the magnesite had the highest solubility; dolomite was least soluble. If the solubility of carbonate rock is determined and plotted on Fig.3, the position of the point on the diagram could indicate the presence of: ( I ) CaCOs alone; (2) CaMg(CO3)z alone; (3) MgC03 alone; (4) mixture of CaC03 and CaMg(C03)~;and (5) mixture of CaMg(CO3)z and MgC03. On the other hand, the solubility of carbonate rock may be estimated if the mineralogical composition of carbonate rock is determined. More research, however, still remains to be done in this field. YANAT’EVA (1957) showed that the region of crystallization of dolomite at a given pcoZ reaches maximum proportions at temperatures between 30” and 45 “C. Inasmuch as pH in sea water tends to respond to and reflect (inversely) pcoZ in the atmosphere, one may conclude that dolomite is stable at a lower pH than calcite; thus, some of’the widespread dolomites of the Precambrian and early Paleozoic times may be primary precipitates out of ancient sea water of lower pH than that of today. Diagenesis of carbonate rocks and mechanism of dolomitization have been discussed recently in detail by CHILINCAR et al. (1967), and by various authors in a symposium edited by PRAYand MURRAY (1965). It is important to mention here that there are ever-increasing investigations of the role of microorganisms in primary precipitation of certain materials in oceans and lakes, as well as studies of diagenetic effects of these organisms. As pointed out by Oppenheimer in the introduction to the excellent work of KUZNETsov et al. (1963): “It can be presumed that much of the transition or diagenesis of inorganic elements and organic compounds in water and sedimentary environments takes place directly or indirectly through the activities of living microorganisms. These microorganisms are indigenous to all environments except volcanic high-temperature sites, and their abundance throughout the hydrosphere and surface of the lithosphere is evidence of their acitvity. They can withstand and be active at pressure up to 25,000 p.s.i., pH from 1 to 10, temperatures from 0 to 75 “C, and salinities up to saturation.” Evidence has been obtained which indicates probable existence of bacteria in sedimentary rocks in excess of 3 billion years. Microorganisms probably have been present in all sedimentary realms throughout all geologic eras and accordingly have affected sedimentary processes. Data on simultaneous deposition of calcite, dolomite (or magnesium calcite) and sulfur, and the role played by bacteria, are not abundant. It would appear that at least two principal mechanisms by which microbiological processes can lead to formation of sulfur in syngenetic deposits have been noted. One is the formation of molecular sulfur by bacteria in a bioanisotropic body of water rich in hydrogen sulfide; the sulfur sinks and is buried in bottom lime-mud. The second is that sulfides can form by reduction of sulfates in water-rich oozes, and after diffusion to the surface layer will be oxidized to molecular sulfur by the bacteria. Such an example seemingly is the bioanisotropic Lake Belovod (U.S.S.R.), which has been described by DOLGOV (1955). Microscopic studies of the surface layer of ooze proved the presence of

INTRODUCTION

7

new crystals of calcite, having been formed by oxidation of calcium sulfide and by the photosynthetic activity of the phytobenthos. One would suppose that molecular sulfur can be deposited in bodies of water only when hydrogen sulfide is formed at a very high rate in the lime oozes. Here, again, is a problem requiring further study. The present book, Carbonate Rocks, Volume B, is an integrated effort of many scientists to bring into sharp focus the tremendous amount of data, ideas, and concepts of physical and chemical aspects of carbonate sediments. The chapters by different authors are reviewed in the order of their appearance in this book. In the opinion of the editors, the volumes (Carbonate Rocks, A and B) represent some of the best thinking of researchers and teachers in this field today. These are people whose lives are dedicated to the development of new ideas and concepts, and to a rigid application of the scientific method. The latter calls for imagination, indeed intuition, but patient testing and practical demonstration are inherent requirements. Although it is now more than 100 years since Henry Sorby first cut a thin-section of limestone, and even longer since Charles Darwin described the modern carbonate environments of the tropic seas, the “loose ends” are numerous and fundamental mysteries still persist as a constant and exciting challenge to successive generations.

ELEMENTAL COMPOSITION OF CARBONATE SKELETONS, MINERALS, A N D SEDIMENTS

Factors determining elemental composition of sedimentary carbonate rocks fall into three groups: (a) initial physicochemicalfacfors (nature of solutions and ions, pH, Eh, temperature and pressure, rates of reactions, etc.); (6) organic factors (direct and indirect metabolic effects, reworking, bacterial processes-even long after burial); and (c) inorganic (diagenetic) factors (modifications to the sediment during and after burial). Numerous components occur in carbonate rocks in only trace amounts; yet in certain cases they appear to play decisive roles. Solid solution (isomorphous) series are particularly important. Of possible importance are the following elements: Mg, Mn, Ni, Fez+, Sr, Ba, Pb, Co, Zn, Ca, Cd. Binary series are better known than polycomponent systems. Some research is being conducted on the possible use of fluid inclusions as indicators of paleoenvironments (either synsedimentary or diagenetic). In Chapter 2, K. H. Wolf, G. V. Chilingar and F. W. Beales discuss the elemental composition of carbonate skeletons, minerals and rocks. They also describe the factors and processes determining the elemental composition; both inorganic and organic processes were covered in considerable detail. The numerous chemical components of carbonates occur in what has been usually termed major, minor and trace quantities. Some elements occurring as traces under certain conditions, are present as minor or even major components

8

R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

under other physicochemical or biochemical influences. On the other hand, certain elements never occur in concentrations beyond that of minute traces in carbonate skeletons, minerals and rocks due to numerous reasons. According to DEERet al. (1962), the following elements have been recorded: (1) calcite-Mg, Mn, Fez+, Sr, Ba, Co, Zn; (2) aragonite-Sr, Pb, Ba, Mg(?), Mn(?); (3) dolomite-Fe2+, Mn, Pb, Co, Ba, Zn, Ca, replacing Mg; less commonly Mn, Fe, Pb, and Mg substituting for Ca; ( 4 ) ankerite-Fe2+, Mn; (5) siderite-Mn, Mg, Ca, Zn, Co; (6) magnesiteFe2+, Ca, Mn, Ni, Co, Zn; (7) rhodochrosite-Ca, Fez+, Mg, Zn, Co, Cd; (8) strontianite-Ca; and (9) witherite-Ca, Mg. It should be noted, however, that many of the above minor and/or trace elements are from high-temperature carbonate minerals. Probably, future research will result in the finding of other elements in these minerals. Elements that occur in sea water in amounts higher than (p.p.m.) are concentrated by organisms 10-100 times that amount. Some of the elements present in the ocean water in quantities less than lO-5% (1 part per 10 million) are also organically utilized. Elements found in biological material and which can be classified as structural elements include C, H, N, 0, P, S, C1, Na, K, F, Mg, Si, and Ca; whereas Fe, Cu, B, Mn, and I are the biocatalysts. Due attention has been given by Wolf et al. to Ca/Mg and Sr/Ca ratios in both organic and inorganic carbonates; and their dependence on temperature, salinity, etc., of the depositional environment was discussed. It is interesting to note here that the maximum MgC03 content of inorganically precipitated calcium carbonate is approximately 4% in contrast to the maximum value of about 30% in organically formed carbonates. CHAVE(1954) demonstrated that aragonitic organisms seldom contain over 1% magnesium carbonate. The Ca/Mg ratio, therefore, also largely depends on the mineralogic form of the carbonate. Non-carbonate material is often present in carbonate sediments. A distinction between primary detrital components and authigenic (diagenetic) minerals is made. The presence of so-called “high-temperature” forms among the latter (e.g., quartz, feldspars, sphene, rutile, tourmaline, etc.) should no longer be a source of astonishment but rather should be used as indicator for reconstructing diagenetic environmental chemistry. The presence of considerable primary organic matter in a carbonate sediment is often the signal for the enrichment of the rock in a wide range of trace elements such as Mo, V, Ni, Pb, Cu, Ag, As, Ge, I and Br. The bacterial liberation of H2S in the syndiagenetic stage is a significant “fixing” process. Inasmuch as some elements present in sea water in the merest traces are selectively concentrated by certain organisms by several orders of magnitude, the nature of the initial biota is of special significance. Among the organisms that are involved in the precipitation of carbonates, it is important to distinguish between (1) the higher phylogenetic groups that secrete carbonates into skeletal material; and (2) those-notably certain primitive Algaethat merely create a favorable microenvironment for precipitation by removal of

INTRODUCTION

9

COz and elevation of pH, and hold the fresh precipitate from dispersal by currents by mats of fine hairs or filaments. The latter are particularly significant in the Precambrian deposits; however, they are still observed in the living state today, particularly in lagoons and tidal flats, i.e., partially isolated but well-illuminated and oxygenated habitats (favoring vigorous photosynthesis). Much attention has been given to the ratios of the various carbonate minerals within sediments and their diagenetic roles. Aragonite/calcite, Ca/Mg, and Ca/Sr ratios, organic components, etc., are of significant importance in skeletal composition and reflect both environments and phylogeny. Of considerable interest is the discovery pioneered by ABELSON (1957), that proteins and amino acids in minute amounts may be analyzed from shells of great antiquity. Some, but up till now very little, attention has been given to the nature of invertebrate shell growth. Because of its biomedical significance,somewhat more is known of mammalian calcification. Isotopic analysis of skeletal material has proved to be illuminating; not only for paleotemperature work (1*0/l60 ratios), but also for salinity determination and for recognizing organic from inorganic microcomponents, notably carbon isotopes. The “law of minimum in ecology and geochemistry” can be’utilized successfully in environmental reconstruction. For developing exploration philosophies (notably in petroleum search) the geochemical techniques involved can be very helpful. As a result of diagenesis-epigenesis, which encompasses a large number of factors and mechanisms, there is an alteration in the content of major, minor and trace elements, and texture and structure of individual carbonate particles and whole rock units. Trace elements are mobilized by diagenesis-epigenesis and metamorphism. In relation to a chemical alteration of carbonates, the numerous diagenetic processes include: (I) inversion: aragonite-calcite; (2) conversion: high-Mg calcite-low-Mg calcite; (3) pseudomorphic replacement: carbonate by carbonate; (4) grain growth; (5) grain diminution; (processes 2-5 are commonly grouped and referred to collectively as “recrystallization”); (6) genesis of non-carbonate components; (7) solution, leaching and bleaching; (8) adsorption-diffusion-absorption; and (9) precipitation of carbonate: cement and nodules. Attention is given to ionic exchange and replacement during advanced diagenesis; compaction of sediments within any sedimentary basin forces migration of fluids, as stressed by NAGY(1960) in his “natural chromatography” concept. Low-grade metamorphism is sometimes induced. Special consideration has been given to an examination of the inorganic physicochemical conditions of precipitation. These conditions today appear to be of very little importance, but may have been predominant in many ancient deposits. Of interest for the idea of a “cold Precambrian” (FAIRBRIDGE, 1964) is ANGINOet al. (1964) recent observation of gypsum, aragonite and mirabilite precipitation in ice-covered Lake Bonney in Antarctica. The presence of dominant Mg in contem-

10

R. W.

FAIRBRIDGE, G.

V. CHILINGAR AND H. J. BISSELL

porary sediments has now been traced to a large range of environments, but always distinct from modern sea water; the implications for interpreting the nature of Precambrian-Paleozoic sea water are forceful but incomplete. A number of examples illustrating changes in the elemental composition with time through the geologic column are presented by Wolf et al. Some of the changes in contents of elements occurring from the Precambrian to the Recent are world-wide (Fig.4). The interpretations of the causes, however, are quite hypothetical and consequently are of a controversial nature. For example, the analyses of numerous limestone samples showed that there is a general increase in the average Ca/Mg ratio in going up the geologic column, with superimposed periodic fluctuations (see CHILINGAR, 1956~).One possible explanation for the evolution of dolomites is the selective return of calcium to the lands. There appears to be a selective weathering of calcium over magnesium in the sediments, and a gradual increase with time of Ca/Mg ratio in solutions contributing to the sea. Permanent loss of muds, which have very low Ca/Mg ratios,. from lands is another reason for the selective and permanent loss of magnesium from the continents. A possible reason for the decrease in Ca/Mg ratio since the Cretaceous time is the fact that pelagic Foraminifera started to extract great quantities of calcium out of the sea water and deposit it in the oceans during and after the Cretaceous time. This calcium is thus withdrawn from the cycle and never returned to the

50-

5 -

v)

n

z

a v)

4-

40I4

O

*

m

3u z

o 2

r

-

3 -

-

.

0

s

2-

'

0

a 4

I-

0,

Z

n

z

30-

0

t P 0

20

-

- .s r" 0

I -

10

CARBONATES OF 4''NORTH AUERICA

I

Pr 23 950

1 600

ABSOLUTE

TIM^

I

Pz

I

I

Mr

1

1Kr

225-m-0IN MILLIONS OF YEARS

Fig.4. Variation of CaO/MgO ratio in clays, sands and carbonate rocks with time. (After RONOV, 1964, p.723, fig.2.)

INTRODUCTION

11

Regional factors are of great interest in considering ancient environments. Arid shores will set up quite distinctive circulation patterns within a basin from temperate well-watered coastlines. Depth distribution can also play a critical role. In Paleozoic rocks dolomite was formerly often considered to be a deeper environmental indicator than limestones, but the evidence from cyclic sequences showed that in many cases the dolomite facies was near-shore (FAIRBRIDGE, 1957). On the Russian Platform through much of the Paleozoic a distinctive nature of circulation reversed this pattern, and phosphorites commonly mark the near-shore facies. Wolf et al. review in some detail the works of Soviet scientists Vinogradov, Ronov, Khain, Teodorovich and others on the changes in Ca/Mg and Ca/Sr ratios through time based on vast numbers of analyses made on the carbonate rocks of the Russian Platform. These results were also compared with the data from North America and the rather sparse information from elsewhere in the world. The modern Mg content drops to 1/25 of its Proterozoic value, whereas the Ca content rises 40% in the same period. Thus there is a marked decrease in the Ca/Mg ratio going back through time. TEODOROVICH (1960) suggested that there has been a progressive change in mode of carbonate genesis through time: (a) Precambrian-Early Paleozoic: direct chemical dolomites; (b) Late Paleozoic: both diagenetic and chemical dolomites; and (c) Mesozoic-Cenozoic: predominantly diagenetic dolomites. VINOGRADOV and RONOV(1956) have shown that these systematic changes affect cements as well as granular components, so that they must be a function of a secular change in environmental fluids, which in turn reflects the progressive evolution of the earth‘s crust. The dynamic nature of the latter, indeed, precludes any possibility that its composition should remain static, although one may visualize perhaps rapid, non-secular steps from one near-equilibrium condition to the next, as successive threshold levels are surpassed (FAIRBRIDGE, 1964). In this way, the total pco2, at or near the earth’s surface, derived basically from “juvenile” volcanic emanations, has been progressively rising through time, but has been controlled and in fact probably decreased sharply at certain stages by solid carbonate removal into buried sediments. Very large deviations of the pco2 through geologic time are ruled out by some scientists on two counts: (a) the buffering effects related to CaC03 solubility in sea water, and (b) the principle of biologic continuity through time, which will not allow gross changes in the atmospheric environment without destroying the planetary biota. Minor phylogenetic catastrophes are allowable and are believed to have occurred. It is believed from the geochemistry of the lithologic record that the pcoZdecreased slowly through the Paleozoic and Mesozoic times, culminating with the vast removal of c0a2-by pelagic plankton in the Cretaceous time. It would be interesting. for imaginative biologists to experimentally control the metabolism of selected primitive marine organisms under conditions of higher pco2, higher Mg2+ and lower Ca2+ concentrations.

12

R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

PHYSICAL CHEMISTRY OF CARBONATES

Modern carbonates laid down in warm, shallow waters consist, for the most part, of metastable minerals (aragonite and high-magnesium calcite) that did not as a rule persist for long periods in the past. Ancient carbonates consist of dolomite and low-magnesium calcite. During lithification (diagenesis) alteration occurs either by solid-state recrystallization (thus preserving original structures as well as Sr/Ca, W / W , and 1 6 0 / 1 8 0 ratios) or by solution and reprecipitation (destroying original features and isotopic ratios). Experiments described by W. H. Taft in his Chapter 3 on the “Physical Chemistry of Carbonates”, show that the metastable aragonite recrystallizes to calcite within 100 days, if submersed in distilled water at room temperature. In nature, however, Holocene shallow marine aragonites maintained constantly in sea water for several thousand years are found to be perfectly preserved. It was found experimentally that the presence of large amounts of magnesium ions ,inhibited inversions; this is true also of strontium, but only in very high concentrations. Recrystallization is accelerated by the rise in temperature, by the presence of certain trace elements, or by the introduction of any ion that tends to lower the pH. Generally, when the natural aragonite or metastable calcite are exposed to rainwater, they rapidly invert to the stable forms. Aragonite forms the cement in beachrock; however, all beachrocks dating from a few thousand years have calcite cements, because during this time they have been subjected to leaching by rain and ground water. Occasionally, dolomite replaces the aragonite or high-magnesium calcite in quite modern deposits. The role of time in some carbonate reactions is just beginning to become recognized. Some dolomite does not form immediately, but instead the disordered form “protodolomite” forms, which only slowly becomes ordered. The protodolomite may be synthetically prepared if Ca2+ and Mg2+ ions are slowly introduced to the solutions containing CO&. For a detailed review on a synthetic formation of dolomite, one may consult CHILINGAR (1956b) and SIEGEL (1961). In sea water, S O P may form a complex with Ca2+ and thus raise the Mg/Ca ratio which is favorable for the dolomite formation. In nature, if a bed of shallow-water metastable carbonates becomes emergent (due, for example, to brief eustatic oscillation), it is likely to be quickly inverted to stable calcite. If, however, the platform is subsiding and the formation becomes covered by other sediments and is subjected to rising connate waters (“anadiagenesis”) rich in Mg2+ and S042- ions, a favorable situation may exist for dolomitization. An alternating (cyclic) sequence of calcitic limestone and dolomite could thus develop. On the other hand, the common association of Paleozoic dolomite layers with higher amounts of insoluble residues suggests rather that they belonged to shallower water environments (FAIRBRIDGE, 1957). Inasmuch as the latter are normally richer in the high-magnesium calcites and aragonites than deeper sedi-

13

INTRODUCTION

ments, the alternation may be controlled by primary differences in carbonate sediment type, which in turn may be in a cyclic sequence of eustatic origin.

CHEMISTRY OF DOLOMITE FORMATION

In Chapter 4,Dr. K. Jinghwa Hsu sums up the present state of knowledge on the long-puzzling problem of dolomite formation. He pointed out that not only must one consider the geochemical conditions appropriate for the formation of the mineral dolomite as a stable phase, i.e., simple discrete crystals, as in abyssal depths of g e northern ocean, but also for the large masses of dolomitic rocks in the geological record which indicate that such conditions must have persisted for considerable periods of time. Experimental data on dolomite formation under surface environments still contain much that is contradictory. For example, the solubility product of dolomite at 25 "C and a pressure of 1 atm., as determined by various investigators, ranges from 10-17 to 10-20. Unquestionably dolomite is present in very recent sediments within a few cm of the surface in some South Australian lagoons, in beachrocks of the Persian Gulf, in the West Indies, and elsewhere under about 1 atm. pressure. Equally well established is the presence of fresh dolomite rhombs in modern deepsea sediments under a pressure approaching 500 atm. and temperature of about 2°C. Under such contrasting conditions wide ranges of pH and Eh are observed; and there is little agreement among the geochemists concerning their respective roles. An increase of temperature, however, evidently increases the rate of dolomite formation. In synthetic dolomites, an elevated pressure has always favored the reaction. At relatively low pressure, GRAFand GOLDSMITH (1956) only obtained what they termed a protodolomite (calcic and with a disordered lattice). Dr. Hsu considers the free energy relations in three hypothetical reactions: CaC03

+ MgC03 + CaMg(CO3)z

(A)

In this case, confusion occurs because MgC03 is found to be not stable in water (marine or fresh) at room temperature and normal pressure, although the free-energy calculation suggests that it is. CaC03

+ MgC03.3Hzo + CaMg(C03)~+ 3Hz0

(B)

Experiments suggest that MgC03. 3Hz0, nesquehonite, is the stable magnesium carbonate in water below 80°C. 4CaCO3

+ Mg4(CO&(OH)z. 3Hz0 + COz + 4CaMg(C03)~+ 4Hz0

(C)

Hydromagnesite is the stable form where the pcoZ is very low. An aragonitehydromagnesite mixture was found as a thin surface layer over the modern South Australian dolomites.

14

R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

It can be postulated that the rate of dolomite formation without catalysis is very slow under normal conditions, and that metastable minerals or mineral pairs form from supersaturated solutions. Organisms may well provide the catalysts. STABLE ISOTOPE DISTRIBUTION IN CARBONATES

Stable isotope distribution in carbonates is discussed by Egon T. Degens in Chapter 5. Calcite, aragonite, and dolomite are composed of four light elements: ( I ) carbon, (2) oxygen, (3) magnesium, and (4) calcium, all of which contain at least two stable isotopes. Most of the stable isotope fractionation in nature apparently is the result of exchange reactions occurring at or near equilibrium. Consequently, knowledge of isotope fractionation factors may reveal information on paleotemperatures, mode of formation, etc. Carbonates exhibit a range of about 12% in 13C/12C ratio. The heaviest carbonates occur in meteorites, whereas the lightest ones are associated with sulfur-evaporite domes (bacterial carbonates). As pointed out by Degens, a great number of marine organisms secrete a carbonate that is slightly enriched in 12C as compared to the value predicted by theory for a system in isotopic equilibrium (CRAIG, 1953; LOWENSTAM and EPSTEIN,1957; WILLIAMS and BARGHOORN, 1963). Thus, the fact that Recent limestones from many areas also show this slight enrichment in 12C content from the expected equilibrium value, suggests that these limestones are in part, at least, a product of life processes in the sea. As a result of even more 12C-enriched C02 contributions to the continental carbon dioxide system, the fresh-water carbonates may be distinguished from carbonates formed in a marine environment; hydrothermal carbonates in contrast are enriched in 13C. Precambrian marine carbonates are often enriched by a few permil (parts per mille) in 1% relative to the average S W of younger limestones, and thus are more like modern lacustrine carbonates. For air oxygen the ratio 1 6 0 / 1 7 0 / 1 8 0 = 99.759/0.0374/0.2039. The data, however, are generally reported in terms of lS0/160 ratio or P O , which is the permil deviation in 180/160 ratio relative to standard mean ocean water (SMOW). A range of about 4% in 1 8 0 / 1 6 0 is exhibited by carbonates; carbonates associated with certain continental evaporite deposits are the heaviest, whereas the igneous carbonatites are the lightest. The temperature dependence of oxygen isotopes allows paleotemperature determinations. Unfortunately, however, the original 1 * 0 / 1 6 0 record, as laid down during deposition, is diagenetically altered. Isotopic equilibration with the surrounding meteoric or connate waters, often intensified by higher temperature, results in an increase in 1 6 0 content of marine limestones and shell carbonates. The original 1 8 0 / 1 6 0 record, even of late Paleozoic carbonates, is preserved, however, under certain post-depositional environments.

INTRODUCTION

15

Isotope studies possibly would also contribute significantly to deciphering the origin of sedimentary dolomite. Dolomites, which precipitated in an aqueous environment at room temperature, should be heavier by ca. 6-10 permil in 1 8 0 over cogenetic calcite or aragonite (CLAYTON and EPSTEIN,1958; ENGELet al., 1958; EPSTEIN et al., 1964). Inasmuch as isotope data of Recent dolomite-calcite pairs from various localities show no significant difference between calcite and dolomite (EPSTEIN et al., 1964; DEGENS and EPSTEIN,1964) one may conclude that these dolomites did not precipitate from an aqueous solution. Thus, dolomite probably was derived by way of metasomatism of calcite, and dolomitization must have proceeded without significantly altering ls0/160 ratio of the precursor carbonate. DEGENS and EPSTEIN(1964) also found this to be true in the case of Paleozoic dolomites. The findings of Degens and Epstein are indeed a major step forward in our understanding of mechanism of dolomitization. The editors of this book, however, believe that further experimental work should be done in this field before reaching absolutely definite conclusions. Inasmuch as the stable isotopes of calcium differ in mass by up to 20% (4OC vs. W a ) , studies on calcium isotopes appear to be promising. There is also 5% variation in the 24Mg/26Mg ratios in dolomites (DAUGHTRY et al., 1962), which warrants further investigation. INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

The joint contribution (Chapter 6) by Bernard Mamet (of Brussels) and Micheline d’Albissin (of Paris) bears the unmistakable stamp of the classical metamorphic limestone studies that have been made over the last century in western Europe. Partly as a result of Mamet’s travels in America it has been possible to blend these data with the concepts developed in the New World by F. Adams, N. Bowen, D. Griggs, J. Handin, F. Turner, J. Verhoogen, and others. Several distinctive stages of alteration are recognized. First of all, simple diagenetic lithification occurs without temperature or pressure changes. Often there is merely a phase change with or without additional cementation and, sometimes, with recrystallization. The latter expression should be used if there are new grain boundaries and the initial fabrics are limited to ghost or palimpsest features. Mamet called the penecontemporaneously recrystallized rock “alpha sparite” and the subsequently altered rock “gamma sparite”. With increased load the pore spaces in loose calcitic mixtures disappear as a result of compaction, and there is a gradual increase in strength and stability. Precise quantitative data on the necessary loading to achieve a certain degree of compaction are lacking, in part because very small amounts of impurities can completely alter the crystallographic reactions, e.g., less than 2% MgO triggers recrystallization, whereas same amounts of clay inhibit it. Studies of microfossil walls, however, offer a fairly good yardstick for such pressure appraisal.

16

R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

With the onset of regional, dynamometamorphic stress, calcite crystals become reoriented (with c-axes parallel to the principal stress). Plastic strain may be expressed by intracrystalline gliding, intercrystalline gliding and finally by recrystallization. The various methods of studying deformed fabrics are also discussed in Chapter 6: infra-red reflection spectroscopy, dilatometry, X-ray diffraction, corrosion patterns, thermoluminescence, etc. In contact metamorphism, Bowen’s thermal decarbonatization series gives the stages of alteration. If magnesium is present, which is usually the case, the series can be complete. In regional metamorphism, the metamorphic limestones react ultimately in the same manner as the surrounding silicate rocks, and consequently the established metamorphic facies series can be identified. An outstanding area of needed research is the progressive reaction of all types of carbonate sediments to simple basin compaction to the equivalent overburden load of 30,000 ft.

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

In Chapter 7, John M. Hunt discusses the origin of petroleum in carbonate rocks. This chapter is a very important contribution, because it has been frequently assumed that petroleum does not originate in carbonate rocks. Thorough studies of both Recent and ancient carbonates, however, show that the amounts of hydrocarbons present in them are comparable to those in clay sediments. Hunt pointed out, nevertheless, that there are certain basic differences in the source and types of organic matter deposited with carbonates as compared to shales. In addition, the rapid lithification of carbonate rocks, as compared to the slow compaction of argillaceous sediments, leads to different conditions of migration. Migration paths are developed through fissures, fractures, and solution channels. Approximately 87 billion barrels of oil are now known to be present in carbonate rocks in major oil fields outside the Soviet Union and other east European countries. Inasmuch as some of these reservoirs are surrounded by carbonate rocks, a reasonable assumption is that carbonates can also be the mother rocks of petroleum. The close association of source and reservoir beds in carbonates, in addition to the frequent presence of impermeable evaporite cap-rocks, probably results in a more efficient process of oil accumulation in carbonate rocks than in sand-shale sequences. Evidences of molecular migration within carbonate source rocks are quite numerous and convincing. There is a possibility for the catalytic generation of hydrocarbons in carbonate rocks, because small amounts of clay are present in many of these rocks. The conversion of organic matter to hydrocarbons in pure carbonates is a thermal process; hydrocarbons could then migrate along the solution and fracture zones.

INTRODUCTION

17

As pointed out by Hunt, this suggests that somewhat greater depths of burial and longer periods of time are required to generate oil in carbonates as compared to clays.

TECHNIQUES OF EXAMINING A N D ANALYZING CARBONATE SKELETONS, MINERALS AND ROCKS

Chapter 8 is devoted to the techniques usually employed for examining and analyzing carbonate skeletons, minerals and rocks. It is the joint work of Karl H. Wolf, A. J. Easton and S. St. J. Warne. Some of these techniques are traditional; others are rather new. Both quick field tests and the more quantitatively precise laboratory tests are described, but space requirements limit detailed treatment to those procedures that seemed to the authors to be the most convenient and appropriate. The basic technique to assist hand lens and binocular examination is the etched surface, which may be produced even under field conditions with a variety of weak acids. This is ideal for a preliminary appraisal of the microfacies, the texture and structure. To distinguish further, for example, between faecal, bahamite and algal pellets, between “open-space” sparite and recrystallization sparite, etc., thin-sections are needed. Even these can be prepared in a field camp with a little ingenuity. Another helpful field procedure, that may also be used in the laboratory, is that of staining. It is essentially limited to grain sizes larger than 0.01 mm. The same is true of spot tests. Both well-lithified and unconsolidated material can also be studied for textures and structures by acetate peel techniques. These are particularly helpful both for the study and easy storage of records of microfacies. These methods also can be applied both in the laboratory and in the field. With the accumulation of large volumes of data, special statistical methods and graphic presentation have been developed. Study of the associated insoluble minerals is often helpful, but care must be taken not to alter them seriously during the separation process (especially in the case of clays). The carbonate minerals themselves are often difficult to distinguish from one another in thin sections. Determination of the refractive index by oil immersion is commonly employed, but overlaps occur in the isomorphous series and hence staining, chromatography, etc., may be used. The universal stage microscope is also helpful. In recent years the electron microscope is rapidly gaining in popularity (with its increasing availability); surface textures of fine-grained carbonates, particularly the organogenic ones, are remarkably characteristic. X-ray radiography is helpful when dealing with mixed terrigenous lithologies. Great care must be taken with aragonite, because it tends to invert to calcite under grinding or during preparation of thin-sections.

18

R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

Methods of chemical analysis have also been presented in Chapter 8 in some detail for the various carbonates as well as for some of the related trace elements. Traditional methods of wet analysis have of late been partially replaced by the use of the spectrophotometric instruments and by the flame photometer. Differential thermal analysis and X-ray diffraction are now standard procedures, and their particular application to the various carbonates are treated in detail in this book. Thermoluminescence is also a phenomenon that has been applied to carbonate study in recent years; it has attracted considerable attention with various objectives in mind, both analytical and paleoecological. Further basic studies, however, are still required in this field. Of invaluable use in determining the rates of sedimentation and the recent ecologic history of carbonate rocks is Urey’s method of 1% age determinations. Many refinements have been added over the last fifteen years, and many anomalies and confusing aspects have been ironed out. The half life of 14C essentially limits the method to less than 50,000 years; however, encouraging research, work on carbonate shells has been made in recent years with uranium-helium, protoactinium and thorium methods that may extend the datable ranges to several million years. Isotope studies have also been widely employed in determining paleotemperatures (1*0/160), in distinguishing organic from inorganic carbonates (13C/W), and for a number of other purposes.

PROPERTIES AND USES OF THE CARBONATES

The economic aspects and practical uses of the carbonates, here discussed in Chapter 9 by Dr. F. R. Siegel, are numerous. Inasmuch as bulk supplies, especially of limestone and dolomite, are often required, accessibility and short transport routes from consumers are of the highest importance. In some parts of the world this is no problem, but in others (notably the Precambrian shield and volcanic regions) there may be serious deficiencies. Annual consumption figures for limestone in a country such as the United States are constantly rising, and indeed may be taken as an approximate index of the gross national product. This is especially true if the year to year figures are seen on a tonnage basis rather than on the sliding scale of a gradually inflating currency. For example, in 1964 crushed stone used in U.S.A. exceeded 700 million tons as compared with less than 450 million tons in 1954. Lime production in 1964 was 19 million tons against 8 million tons in 1954. Portland cement output was 360 million barrels in 1964 against 290 million barrels in 1954. Some 100 uses are listed for limestone, dolomite and marble (Table XI11 in Chapter 9). Some are employed directly as for building stone (known technically in the U.S.A. as “dimension stone”); others indirectly as in the chemical industry

INTRODUCTION

19

(e.g., “whiting”, see over 70 uses listed in Table XIV in Chapter 9), glass manufacture, or in sugar refining. Other carbonate minerals are not found in large rock-forming deposits as is the calcium-magnesium group; they are mainly utilized as metal ores and in the chemical industry. These include rhodochrosite, an ore of manganese, also used as a pigment “manganese white”; siderite, an iron ore; smithsonite, a zinc ore and pharmaceutical; witherite, a barium ore, also used in sugar refining, as a rat poison, in paints, and in glass and paper industries; strontianite, a strontium ore, also used in sugar refining, in paints, glass and in pyrotechnics; cerussite, a lead ore, also used in paints, for putty and in “leaded” paper; malachite and azurite, copper ores and ornamental stones such as vases and table tops; and trona, a sodium ore, used in the glass, paper, soap and other chemical industries. Modern research is constantly opening new areas of use for the carbonates. The new “oxygen process” for steel smelting uses twelve times more limestone than do conventional refractory methods. Consumption, even of the simple crushed rock, will rise inevitably. A natural by-product of limestone country is the geomorphic phenomenon, the “karst” landscapes and caverns. Whereas the waterless land surface may be poor for agriculture, it is sometimes more than offset by the valuable tourist attractions of the caves, with their stalactites and stalagmites, underground streams and speleological interests. Karst systems (if adequately sealed) also offer a potential for underground storage of gasoline, etc. Another group of limestone geomorphic phenomena of very considerable tourist value are the coral reefs, and the related island-life charms extending across the tropical Pacific and Indian Oceans. The rather minor, though more accessible, examples in the Atlantic include those in Florida, the Bahamas and West Indies. REFERENCES

In reviewing various chapters in this book, in many instances the editors quoted the same authors whose names appear in the reference lists of particular chapters; these references are not repeated here.

ALEKIN,0. A., 1953. Principles of Hydrochemistry. Gidrometeoizdat, Leningrad, 296 pp. ATWATER, G. I., 1965. American Association of Petroleum Geologists, Distinguished Lecture Series. Based on: ATWATER, G. I. and MILLER,E. E., 1965. The effect of decrease in porosity with depth on future development of oil and gas reserves in South Louisiana. 27 pp., unpublished. BARON,G. et FAVRE, J., 1958. ktat actuel des recherches en direction de la synthese de la dolomie. Rev. Znst. Franc. PJtroIe Ann. Combust. Liquides, 13(7-8): 1061-1085. CHILINOAR, G. V., 1956a. Solubility of calcite, dolomite, and magnesite, and mixtures of these carbonates. Bull. Am. Assoc. Petrol. Geologists, 40: 2770-2113. CMLINGAR, G. V., 3956b. Note on direct precipitation of dolomite out of sea water. Compass, 34: 29-34. CIIILINOAR, G. V., 1956c. Relationship between Ca/Mg ratio and geologic age. Bull. Am. Assoc. Petrol. Geologists, 40(9): 2256-2266.

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R. W. FAIRBRIDGE, G. V. CHILINGAR AND H. J. BISSELL

CHILINGAR, G. V., 1956d. Abundance of carbonate rocks in European U.S.S.R.: a summary. Bull. Am. Assoc. Petrol. Geologists, 40 (8): 2022-2023. CHILINGAR, G. V. and BISSELL,H. J., 1961. Dolomitization by seepage refluxion (Discussion). Bull. Am. Assoc. Petrol. Geologists, 45(5): 679-681, CHILINGAR, G. V. and BISSELL,H. J., 1963a. Formation of dolomite in sulfate4hloride solutions. J. Sediment. Petrol., 33: 801-803. CHILINGAR, G. V. and BISSELL, H. J., 1963b. Note on possible reason for scarcity of calcareous skeletons of invertebrates in Precambrian formations. J. Paleontol., 37: 942-943. CRICKMAY, G. W., 1945. Petrography of limestones. In: H. S. LADDand J. E. HOFFMEISTBR (Editors), Geology of Lau, Fiji-Bernice P. Bishop Museum Bull., 181 : 21 1-250. DOIGOV,G. I., 1955. Sobinskiye Ozera. Trudy Vses. Gidrobiol. Obshchestva Akad. Nauk S.S.S.R., 6: 193-204. EREMENKO, N. A. (Editor), 1960. PetroleumGeology (Handbook), I . PrinciplesofPetroleumGeology. Gostoptekhizdat, Moscow, 592 pp. FAIRBRIDGE, R. W., 1957. The dolomite question. In: R. J. LEBLANC and J. G. BREEDING (Editors), Regional Aspects of Carbonate Deposition-Soc. Econ. Paleontologists Mineralogists, Spec. Publ., 5 : 125-178. FAIRBRIDGE, R. W., 1964. The importance of limestone and its Ca/Mg content to paleoclimatology. In: A. E. M. NAIRN(Editor), Problems in Paleoclirnatology. Wiley, New York, N.Y., pp.431-530. S. I., IVANOV, M. V. and LYALIKOVA, N. N., 1963. Introduction to Geological MicroKUZNETSOV, biology. McGraw-Hill, New York, N.Y., 252 pp. G. V. (Editors), 1966. Diagenesis in Sediments. Elsevier, AmsterLARSEN,G. and CHILINGAR, dam. (In press.) NAGY,B., 1960. Review of the chromatographic “plate” theory with reference to fluid flow in rocks and sediments. Geochim. Cosmochim. Acta, 19: 289-296. PRAY,L. C. and MURRAY, R. C., 1965. Dolornitization and Limestone Diagenesis ( A Symposium) -Soc. Econ. Paleontologists Mineralogists, Spec. Publ., 13: 180 pp. G. V. and ROBERTSON RIEKE111, H. H., CHILINGAR, JR., J. O., 1964. High-pressure (up to 500,000 psi) compaction studies on various clays. Intern. Geol. Congr., 22nd, New Delhi, 1964. (In press.) RONOV,A. B., 1964. General tendency in the evolution of composition of earth crust, ocean, and atmosphere. Geokhimiya, 1964(8): 715-743. RUKHIN, L. B., 1961. Principles of Lithotogy, 2nd ed. Gostoptekhizdat, Leningrad, 779 pp. (In Russian.) JR. J. W., and CRICKMAY, SANDERS G. W., 1945. Chemical composition of limestones. In: H. S. LADDand J. E. HOFFMEISTER (Editors), Geology of Lau, Fii-Bernice P . Bishop Museum Bull., 181: 251-259. SIEGEL,F. R., 1961. Factors influencing the precipitation of dolomitic carbonates. State Geol. Surv, Kansas, Bull., 152(5): 127-158. SVERDRLJP, H. U., JOHNSON, M. W. and FLEMING, R. H., 1962. The Oceans, Their Physics, Chemistry, and General Biology, 4th ed. Prentice-Hall, New York, N.Y., 1087 pp. J. W., 1964. Modern carbonate sediments of southern Florida, TAFT, W. H. and HARBAUGH, Bahamas, and EspIritu Santo Island, Baja California: a comparison of their mineralogy and chemistry. Stanford Univ. Publ., Univ. Ser., Geol. Sci., 8(2): 133 pp. VALYASHKO, M. G., 1962. Geochemical Regularities in the Formation of Potassium Salt Deposits. Izd. Moskov. Univ., 397 pp. VINOGRADOV, A. P., 1953. The Elementary Chemical Composition of Marine Organisms. Sears Foundation for Marine Research, Yale Univ., New Haven, Conn., Mem., 2: 647 pp. J. M., 1959. Compaction of sediments. Bull. Am. Assoc. Petrol. Geologists, 43(2): 273-310. WELLER, YANAT’EVA, 0. K., 1950. The solubility of dolomite in aqueous salt solutions. Izv. Sektora Fiz. Khim. Analiza, Inst. Obshch. Neorgan. Khim., Akad. Nauk S.S.S.R.,20: 252-268. YANAT’EVA, 0. K., 1954. About physical-chemical characteristic of some carbonate rocks. Dokl. Akad. Nauk S.S.S.R.,96(4): 717-719. YANAT’EVA, 0.K., 1957. On the solubility polytherm of the system (CaCOs MgSO4 $ CaS04 MgCOs) - HzO. Proc. Acad. Sci. U.S.S.R.(Chem.Sect., English Transl.), 1957: 155-151.

+

+

21

INTRODUCTION

APPENDIX A COEFFICIENTSFOR CONVERTING mg/l TO rng-equiv./l

Ions

1

(rng/l

Equivalent weight

Coefficient

20.035 (20) 12.16 22.997 (23) 18.03 30.0 48.03 (48) 35.476 (35.5) 61.0 46.0 62.0 17.0

0.0499 0.0822 0.0435 0.0554 0.0333 0.0208 0.0282 0.0164 0.0217 0.0161 0.059

See also EREMENKO (1960).

-

COEFFICIENT

= mg-equiv./l)I

Chapter 2 ELEMENTAL COMPOSITION OF CARBONATE SKELETONS, MINERALS, AND SEDIMENTS K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES Department of Geology, The Australian National University, Canberra, A.C. T. (Australia)' Department of Petroleum Engineering, University of Southern California, Los Angeles, Cal$ (U.S.A.) Department of Geology, University of Toronto, Toronto, Ont. (Canada)

SUMMARY

Emphasis is laid upon the basic chemical, organic, and inorganic principles that determine the composition of carbonates. Elemental compositions vary considerably depending on numerous primary and secondary factors. Their significance has been documented by selected published examples. The practical applicability of elemental analyses of carbonates is stressed, and some case histories provide evidence that the chemical make-up of both the carbonates and associated non-carbonate components can be useful indicators of the original environmental conditions. It is hoped that data compiled here are sufficient to stimulate further research in this interesting field of sediment geochemistry.

INTRODUCTION

Carbonate minerals and rocks form in nature over a wide range of environmental conditions and their composition is controlled largely by their mode of genesis. In addition to constituting approximately 10-1 5 % of the sedimentary deposits, carbonates occur also in certain varieties of igneous and metamorphic rocks. In general, therefore, carbonates can be divided into high- and low-temperature types. The present contribution, however, deals almost exclusively with the low-temperature and low-pressure carbonate minerals and rocks. Further, inasmuch as a comprehensive summary of many of the aspects related to sedimentary carbonates has been presented recently by a number of workers such as REVELLE and FAIRBRIDGE (1957), and GRAF (1960), the authors confined themselves to the discussion of selected fields covering only some of the many facets of the elemental composition

Present address: Department of Geology, Oregon State University, Corvallis, Ore. (U.S.A.).

24

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

of carbonates. A summary of the absolute values of chemical elements appears to be premature in view of the rapid advances in both compositional data and concepts of genetic mechanisms. Hence, no pretense is made of completeness and much of the information presented here is of necessity sketchy and superficial. Where a choice has had to be made between brief citations, or more complete coverage of fewer examples, the authors have favored the policy of reference to as many different publications as space permitted. Numerous gaps are only too apparent in the present state of our knowledge. For example, RONOVand KORZINA (1960) pointed out the gap in our knowledge between highly concentrated mineral deposits on the one hand, and the dispersed trace minerals and trace elements on the other.

FACTORS AND PROCESSES DETERMINING THE ELEMENTAL COMPOSITION OF CARBONATES

Some details of materials, conditions, and processes that control the composition of carbonate minerals, skeletons and rocks are given in other chapters. By way of introduction, and to emphasize the complexity of inter-relationships, however, some of the factors and processes that are considered in other chapters are listed as follows: Physicochemicalfactors (I) (2) (3) (4) (5)

(6) (7)

(8) (9)

Composition of solution (type of ions present). Concentration of ions present. Ionic potential (= property of ions). pH (= property of solutions). Eh (= property of both solutions and ions). Temperature and pressure. Rate of reactions. Solubility of the various possible compounds that can form. Absolving property of water medium and other fluids (GOTO,1961).

Organic influences (I) Direct metabolic processes (e.g., processes which control composition of both carbonate skeletons and organic matrix). (2) Indirect influences by changing environment (e.g., metdbolic processes of animals and plants may change pH, Eh, and ion-concentration of water medium). (3) Biotic reworking (e.g., mud-eater may cause chemical alteration of carbonate sediments in digestive system before excretion as fecal pellets occurs). (4) Bacterial processes (although strictly referrable to items 1 and 2 above,

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

25

solution, deposition, and transformation of carbonates and solutions by Bacteria is a sufficiently important topic to warrant separate mention), e.g., post-humous decomposition of organic matter (gases, fluids, and ions are liberated to the surrounding environment as a result of decomposition), sulfate reduction and so on. Inorganic processes

( I ) Precipitation (e.g., deposition of aragonite, low-Mg calcite, etc., by evaporation). (2) Solution (e.g., selective removal of more soluble carbonates). (3) Leaching (e.g., selective removal of ions from carbonate minerals and skeletons without actual solution). ( 4 ) Oxidation and reduction. (5) Adsorption-diffusion-absorption (e.g., differential uptake of ions by clay minerals and both living and dead organic matrix). (6) Replacement (e.g., replacement of carbonates by carbonates or by noncarbonates). (7) “Recrystallization” (a number of processes included here can change the composition of the carbonates). (8) Extraneous contribution (e.g., terrigenous, volcanic, and cosmogegcpus). Two important factors have to be taken in consideration in all discussions on the chemical composition of sediments, namely, first, the limitations of the methods and instruments employed, and second, the “human” factors involved in collecting samples, and others (LAMARand THOMPSON, 1956). Numerous sensitive stability ranges and geochemical thresholds clearly control the equilibria involved in carbonate-rock formation. Numerous examples of complete alteration and many reversible reactions are well documented in the literature. Probably even more serious at the present time is our lack of knowledge of the relationships between organogenic and purely physical processes in carbonaterock formation. Organic processes undoubtedly predominate in providing the raw materials from which the bulk of Phanerozoic (post-Precambrian) limestones have formed. The course of their subsequent diagenesis has largely depended on physical processes. Many direct and indirect inter-relationships undoubtedly occur and will be the subject of much research in future years. It is hoped that this partial compilation of ideas will assist both assessment of the present state of our knowledge and the research that will advance our understanding further.

ELEMENTAL COMPOSITION OF CARBONATE SKELETONS, MINERALS, AND ROCKS

In a general way, the numerous chemical components of carbonates occur in what has been usually termed, major, minor, and trace quantities. Where cations can

26

K. H.

WOLF, G.

V. CHILINGAR AND F. W. BEALES

form a partial or complete solid solution, the ionic species can be expected to occur in either major or minor quantities, or as minute traces. Considering particular solid solution series, it has been found that elements occurring as traces under some conditions, will be present as minor or even major components under other physicochemical or biochemical influences. On the other hand, certain elements never occur in concentrations beyond that of minute traces in carbonate skeletons, minerals, and rocks due to numerous geological and chemical reasons as illustrated here. The writers refrained from setting precise boundaries between the major, minor, and trace elements as they would serve no purpose in the present discussions, especially in view of the uncertain chemical affinities of the components in many cases. The chemistry of sedimentary carbonates is in general divisible into the following aspects: ( I ) isomorphism (= solid solution) of carbonate minerals, (2) minor and trace elements in carbonate minerals, (3) “fluid inclusions” in carbonates, and (4) non-carbonate components in carbonate sediments. Each aspect is considered briefly as given below. Isomorphism of carbonate minerals

Complete low-temperature isomorphous substitution of one cation by another is possible in the following cases: - rhodochrosite (MnCOs) calcite (CaC03) dolomite (CaMg(CO3)z) - ankerite (CaFe(CO3)z) - siderite (FeC03) magnesite (MgC03) rhodochrosite (MnC03) - siderite (FeC03) strontianite (SrC03) - witherite (BaC03); isomorphous only in artificial material. High-temperature solid solutions (not further considered here) are discussed in the following references (among others): (1 963) for ROSENBERG MgC03-FeCO3, and MnC03-FeC03 ROSENBERG (1 963) for CaC03-FeC03 HARKER and TUTTLE ( 1 955) for CaC03-MgC03 GOLDSMITH (1959) for CaC03-MgC03, CaC03-MnC03, and CaC03FeC03 CaC03-MgC03-FeC03 GOLDSMITH et al. (1 962) for CHANC(1 963) for BaC03-SrC03, SrC03-CaC03, and BaC03CaC03 GOLDSMITH et al.( 1955) for MgC03-CaC03 CHAVE (1 952) for CaCOs-CaMg(CO3)z (of low-temperature origin) HOLLAND et al.( 1963) for Zn and Mn coprecipitated with calcite; and Sr content of calcite and other carbonates.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

27

Reference can also be made to general publications such as those by GRAF and LAMAR (1955), GRAF(1960), GOTO(1961), and DEER et al. (1962). Rare carbonate minerals are not discussed in this chapter although they most certainly will be of definite interest in future petrologic studies: in particular those concerning diagenesis. ALDERMAN (1959), for example, pointed out that huntite (CaMg3 (C03)4), which usually forms as a weathering product of dolomite and magnesite, may prove to be more widespread than is generally assumed. Minor and trace elements in carbonate minerals

According to DEERet al. (1962), the following elements, in addition to the major ones given in the formulae above, have been recorded: (1) calcite-Mg, Mn, Fez+, Sr, Ba, Co, Zn; (2) aragonite-Sr, Pb, Ba, Mg(?), Mn (?); (3) dolomite-Fe2+, Mn, Pb, Co, Ba, Zn, Ca, replacing Mg; less commonly Mn, FeyPb, and Mg substituting for Ca; ( 4 ) ankerite-Fez+, Mn; (5) siderite-Mn, Mg, Ca, Zn, Co; (6) magnesite-Fez+, Ca, Mn, Ni, Co, Zn; (7) rhodochrosite-Ca, Fez+, Mg, Zn, Co, Cd; (8) strontianite-Ca; and (9) witherite-Ca, Mg. It should be noted, however, that many of the above minor and/or trace elements occur in high-temperature carbonate minerals. Probably, future research will show presence of other elements in these minerals. According to LOGVINENKO and KOSMACHEV (1961), mainly binary series of isomorphism are described in the literature, whereas information on polycomponent systems such as (Fe, Ca, Mg, Mn)C03 are scarce or lacking. In many cases, the minerals have been identified by optical, X-ray, thermal, staining, and other methods as ones of simple composition, and none of the other elements were detected in spite of their presence in comparatively large amounts. In this regard the binary nomenclature (e.g., ferroan calcite, breunnerite) is misleading. For example, LOGVINENKO and KOSMACHEV (1961) determined the composition of diagenetic carbonate concretions to be ( F ~ s z . z ~ - s s . ~Ca7.39-12.96, z, Mnz.45-3.10, Mg0.34-5.26) CO3. (A similar occurrence has been quoted in the chapter on techniques of analyzing carbonate skeletons, minerals, and rocks -WOLF et al., 1967.)

Fluid inclusions in carbonates Inter- and intra-crystalline fluid inclusions in calcite and dolomite minerals are mentioned by LAMAR and SHRODE (1953) and SHOJIand FOLK(1964). The former two investigators examined water-soluble .salts in carbonate rocks and concluded that “much of the calcium and sulfate (excluding calcium dissolved from the calcite and dolomite) probably occurs as intergranular solid calcium sulfate with magnesium sulfate possibly occurring in the same manner”. As thin-section and decrepitation studies suggest, however, “the sodium, potassium, and chlorides,

28

K. H.

WOLF, G.

V. CHILINGAR AND F. W. BEALES

together with some calcium, magnesium, and sulfate, are probably present primarily in solution in intragranular fluid inclusions”. SHOJIand FOLK(1964) found fluid inclusions in calcite during electronmicroscopic investigations of carbonates. The calcites are often spongy due to densely crowded bubbles. The above authors suggested that the inclusion-rich calcite formed in environments that lacked clay-sized carbonate and where the sea water was relatively clean. The sponginess of the calcite may affect dolomitization. Influences on other diagenetic processes by these fluid inclusions may also be expected. As to what extent these fluids can be used in environmental reconstructions remains to be determined by future research (WEBER,1964b). Non-carbonate components in carbonate sediments

Non-carbonate components in calcareous sediments are inorganic or organic in composition. The sum total of organic matter from diverse sources has a considerable influence on the cation composition of sediments. The non-calcareous material is either syngenetic, diagenetic or epigenetic in origin according to one consideration (see CHILINGAR et al., 1967) and either detrital or authigenic from another view-point. When attempting to separate the non-carbonate from the carbonate fraction, it is significant to consider that not all non-carbonate fractions are “insoluble” (see WOLFet al., 1966). GRAF(1960) gave a list of authigenic minerals that have been reported from carbonate sediments. This list included fluorite, celestite, zeolites, goethite, barite, clay minerals, phosphate, pyrolusite, gypsum, feldspar, micas, quartz, sphene, rutile, glauconite-chlorite, tourmaline, pyrite-marcasite, rare carbonate minerals, and a host of others, that can form at the surface or within the carbonate sediments. In general, one of the most significant and widespread contaminants of sedimentary carbonates is the clay fraction. The adsorption and ion-exchange ability of the clays makes them valuable as environmental indicators that may assist in distinguishing between fresh-water and marine limestones. DEGENS et al. (1958) showed that the clay fraction of these two types of calcareous sediments have significant mean differences in boron and gallium contents; and that the interpretations as to whether they are fresh-water or marine deposits agree in 80% of the cases examined, where previous environmental reconstructions were based on fossil evidence. WALKER (1964) has done some similar work on the boron content of clays. GULYAEVA and ITKINA (1962) found that clays and argillites of fresh-water facies differ from those of marine deposits in having lower halogen contents and low CI/Br and Br/l ratios, as given in Table I. To what extent the observations on the halogens apply to clays derived from carbonate sediments remains to be seen. Both skeletal and inorganieally formed carbonate sediments commonly contain organic matter, in particular in the early stages of sedimentation. In both

29

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

TABLE I RATIOS OF

Br/I

AND

CI/Br I N SOME MARINE AND FRESH-WATER CLAYS

(After GULYAEVA and ITKINA,1962) Marine clays

Br/I CI/Br

8.8- 16.3 75 -170

Organic-rich marine clays

5- 6 45-64

Fresh-wafer clays ~-

~

2.2-2.7 5. I

living and post-mortem stages, the organic matter controls to a marked degree both minor and trace elements in the bulk composition of carbonate skeletons and rocks, as mentioned above. For example, GOLDSCHMIDT (1 937), GOLDSCHMIDT et al. (1948), and KRAUSKOPF (1955) stated that carbonate sediments rich in organic matter may be enriched in Mo, V, Ni, Pb, Cu, Ag, As, Ge, I, and Br (see also GRAF,1960). KRAUSKOPF (1955) suggested that Pb, Zn, Ni, and Cu may react with H2S liberated from decaying organic matter and precipitate as sulfides. Similar correlations exist between inorganic components and trace elements. For instance, sediments containing manganese oxide have been known to be enriched in Co, Mo, and Ba; and phosphatic limestones often contain F and CI in the structure of the phosphate minerals. K. G. BELL(1 963) stated that carbonate rocks that are composed wholly of carbonate minerals and contain only traces of other constituents generally have about 0.0001 %, or less, of syngenetically precipitated uranium. The impure carbonates, however, may contain 0.OOOX-O.OOX% of' uranium. This element is associated with phosphatic, organic and detrital components mainly; and, according to K. G . Bell, no appreciable amounts of uranium can be expected in the carbonate fraction itself. Both the fluid inclusions and numerous types of non-carbonate constituents mentioned above make it extremely difficult to determine the form of occurrence of the major, minor and trace elements present in skeletons, minerals and rocks. Thus, in many studies elaborate techniques had to be devised to achieve a separation of the different fractions. The chemical data given in Table I1 and 111 can, therefore, be used only as general guides to the elemental composition of carbonates; much more research is required before the actual distribution of all elements can be demonstrated and predicted.

TABLE I1 TRACE-ELEMENT COMPOSITIONOF CARBONATEAND NON-CARBONATECONSTIWENISI

Ag

Limestones

P--G 4 p.p.m.

Dolomites

PG

“Carbonates”

P--G 20 p.p.m.

“Insolubles” Clays “Heavies” Organic matter Bitumen Algae Phaeophyceae

Rhodophyceae

Chlorophyceae

Corallinaceae

A1

As

B

Ba

P-G

P--G

PG

p.p.m. P--G

P--Gp--G

p.p.m. F - G

Au

P--G 15 p.p.m.

65 p.p.m.

0.009

p.p.m.

S-FM

1.2.10-6

g/g d.m. P--v

Bi

s-V,FM

2.10-8

g/g d.m.

6,000

p.p.m. P--G p--G P--G

C

Ca

P--G 15 p.p.m.

2,000

8,000

P--G 3 p.p.m.

P--G

p--G P-G

p.p.m. P--G

Br P--G 10 p.p.m.

200 p.p.m. 10,000

0.5 p.p.m.

P--v

Be

x

8

P-G

“Q

p-v

P--v

P-v

9

P-v

5

10 mgl 100 g d.m.

s-v

p-v

P--v

0

1.m.

d.m.

2

P--v

p-v

$ger

1.2 mg/ 100 g d.m.

s-v

CaO of ash P-V

1.m.

d.m.

CaO of ash

2 tl w

P--v

s-v

0.08 mg/ 1,OOo g

d.m.

0.044%

0.7%

0.02%

1.m.

43%

28%

p-v

46% d.m.

64%

89 %

P-v

60 %

CaO of ash h-V,K

99.3 %

CaC03

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ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

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ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

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ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

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ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

00 & n182 -

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Arthropoda Trilobita Crustacea

P--v 7.7 % d.m.

Echinodermata

s-v 0.0016% 1.m. s-v

Echinoidea

s-v 0.52 % 1.m.

0.05 %

P-V

P - G 25 p.p.m.

3

E

h-V 7 10-5% d. wt.

Crinoidea Annelida

d

8 z s-v 6.73 % d.m.

-

Mg

Limestones Dolomites “Carbonates” “Insolubles” Clays “Heavies” Organic matter Footnote is given on p.49

s-v 0.651 % d.m.

s-v 2.22 % KzOd.m.

s-v

v)

m

8

5

~~

Mn

Mo

P--G

P--G 22 p.p.m.

3,200 p.p.rn. p--G 4,100 p.p.m. P - G 2,800 p.p.m.

p--G 1.2 p.p.m. P--G 70 p.p.m.

P--G

B 5 F 0 0

s-v

d.m.

m

G

N

Na

P--G 150 p.p.m. P--G 240 p.p.m.

P - G

Nd

Ni P--G 70 p.p.m.

P--G 14 p.p.m. P--G 100 p.p.m. P--G 190 p.p.m.

P

Pb

P--G 100 p.p.m. P--G 8 p.p.m.

Pr

Ra P--B 58 glg

. 10-14

2

ga 4 cl

*

E 2

sE

P--G 200 p.p.m. P--G

P--G

P--G

P--G w

\o

TABLE I1 (continued) Mg

Mn

Mo

N

Na

Nd

Bitumen p-V,FM

Algae Phaeophyceae

Rhodophyceae

Chlorophyceae

Corallinaceae

Rryozoa

P V 15% MgO of ash P--v 15% MgO of ash P V 9.7% MgO of ash p-V,G II % MgO of ash h-V,G 11%

Protozoa Foraminifera "Globigerina ooze"

P--v

1.0 * 10-6

MgC03 wt.

P--v 0.015% d.m.

g/g d.m.

P--v 4.8 % d.m.

P--v 0.036% d.m.

P--v 6.6 % d.m.

P-V 0.008 "/, d.m.

P-v 5.6 d.m.

p-V,G 0.02% d.m.

P--v

p-V,G,S, p-H,G,S BT 0.1 % >25 mol% p-G 2,600 p.p.m.

Ni

P-G

P-V

p-v P--v 5.9 % PZo5 of ash P--v 46.5 % pzos of ash P--v 4.8 % pzos of ash h-V,G

P--v 34 % NazO of ash P--v 27 % NazO of ash

P-v

22.2 % NazO of ash P--v 2.8 % Nan0 of ash

0.5%

P --G

P-G 60 p.p.m.

Pr

Ra

p-v

p-v

F

r

p-G 0.8 p.p.m.

CadPWz wt. h-G 8.5% p-V CadPO& wt.

P--s
Pb

P-G 120 p.p.m.

P--v

p-G 3 p.p.m.

P

P-GS 0.01 7; P-G 360 p.p.m.

FFJ

Porifera

Calcarea

Coelenterata Hexacoralla Octocoralla

Hydrocorallina

Medusae Brachiopoda Inarticulata

Articulata

Mollusca

h-G,V 14.1 % MgC03

p-V

p-v

wt.

p-v

8.4 % d. wt.

P-v

14.1 MgC03 of ash h-S1 0.31 %

p-V

P-V 16.7% NazO of ash

wt.

P--v 8.6 % pZo5 of ash P-v 1.2%

.

' 8

8

8z

pzo6

p-v p-v p-v 0.0055% 0.0018% 0.2% d.m. d.m. 1.m.

P--v 1%

1.m.

P-V 0.003 % d.m.

V G P-, 0.46% Mn304 in ash

P-V,G 8.6 % M&03 wt. s.h-V O-V 38% 2.5% MgC03 d.m. of residue

Footnote is given on p.49

E?

p-SH p-B 0.028 105 p.p.m. wt. g/g

wt.

G-P 6.7% MgC03

PV

p-SH 0.71 p.p.m. wt.

s-v 13.7% d.m. 2.2 % 1.m.

h-V,G 16.7% MgCO3

h-V,G 8.5 % MgC03 of ash p-v 0.118% d.m.

h-G,V

9.1 % pZo5 of ash

S-V

s-v 11.6% d.m.

s-v I .34% 1.m.

s-v 0.004%

$m.

of ash p-v 0.33% 1.m.

p-v 0.0043% d.m.

P-V,G 93.7 % CadP04h of ash PV,G 0.61 % Caa(P04)z of ash s,h-V S-V 5.9% 0.015% PZOSof d.m. residue P

TABLE I1 (continued) ~

Mg

Pelecypoda

Cephalopoda

Arthropoda

Mo

N

Echinodermata

Rhinoidea

Nd

Ni

P

Pb

h-G h 4 0.40% 1.4 p.p.m. wt. Ca3(PO& h-G

440

MgC03 wt. p.p.rn. pG,KB p4,KB p P G 438 PG,TAO, PG TAI 2.4% 0.059% p.p.m. MgCO3wt. wt. p-G,TAI p T A I 7% > 7,000 MgCOa p.p.m.

0.85 % wt.

Ca3(P04)~

h 4 trace

h-G 1 p.p.m.

wt.

Trilobita Crustacea

Nu

p--GJ'G P-V,G, TA0,TAI PG 2.8%

Gastropoda

Mn

l--G 2,700

s,h-V,G 1%MgO S-V d.m.; 16 % 0.025 % MgC03 d.m. of ash S,h-V S,h-V 15%

MgC03 of ash h-G 16%

MgC03

wt.

p.p.m. s-V

0.0028% s,h-V

d.m. h

4

h-G

p.p.m. d. wt.

d.wt.

530

-

1 10-5%

s-v

16.9 %

s-v

0.65 %

d.m.

1.m.

s-v

s-v

S-V

pV,G

s,h-V

1.12%

50% s,h-V CadP04h wt. S,h-V S,h-V

0.0021%

Ca3(P0& in tissue ash residue h-Gh-G 2.1 p.p.m. 5 p.p.m. d. wt. d. wt.

Pr

Ra

P-B

78 . 10-14

g/g

E

4

0,

4

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e

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

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TABLE 11 (continued) Rb

Re

S

Sb

sc

Se

Si

Sn1

Sn

Sr

Tb

~~

Rhodophyceae

P-v

P-v

so8

Si02 of ash

44.2 %

16.4%

of ash P--v

Chlorophyceae

P--v 26.7 %

39 % SO3

SiOz of ash P--v

of ash P--v

Corallinaceae

6.9 %

8.4 %

so3

Bryozoa

ooze”

Porifera

Calcarea

SiOz of ash P--v

CaS04 of ash

Si02 of ash

8.5 %

Protozoa Foraminifera

“Globigerina

of ash P--v

PVS,

P--v
P--G

0.05 %

P--v 8.6% so3

of ash P--v

1.97 %

CaSOa d. ash

h-G

16.7 %

94.7 %

RbzO

h-G h-G .0.7 p.p.m. 2,200 p.p.m.

p-V

SiOz of ash

A

F

3,100

p.p.m. h-S

0.01 %

h-S

p 3

h-G

U

10%

P-G

160

P--v

99.2 %

SiOz of ash

p.p.m. p-V

1,500

p.p.m.

Coelenterata Hexacoralla

P--v 0.9 % CaSO; of ash P--v 5.4 % CaS04 of ash P--v 2.14% CaS04 of ash P--v 0.19% 1.m.

Octocoralla

Hydrocorallina

Medusae Brachiopoda Inarticulata

Articulata

Mollusca

Pelecypoda

Footnote is given on p.49

S-FM 4.6.10-9 g/g d.m.

P--v 8.37 % CaS04 of ash P--v 2.4 % CaS04 of ash s,h-V 2.82 % CaS04 of residue

P--v 1.25% SiOz of ash

PB -G ,, s1 < 1.2 % P--G 8,700 p.p.m.

P-SH 0.08 p.p.m. wt.

P-v

P--v 0.00002 % d.m.

1.7% SO:! of ash P--v 0.63 % SiOz of ash

P--v 0.9 % SiOz of ash

P--v 0.6 % SiOz of ash

P-SH 0.0058 p.p.m. wt.

P-G 6,200 p.p.m. P--G 9,300 p.p.m. P--v 0.003 % d.m. P--v h-G 1,300 p.p.m. S,h-V,B s,h-V 0.6% 92.9% of residue SiOz of residue h-G p-G,PG, 0.8 p.p.m. TA0,TAI 10,Ooo p.p.m.

R

Ir

9

4

4 E

Y

4

G 4

Y

9

Y

4 Is:

9

4 0

ea

*

8

40

m

-8 c

u3

E

I a

>

v)

I

>

K. H. WOLF. G. V. CHILINGAR AND F. W. BEALES

2

0 i j 18 a-

Limestones

Th

Ti

p--C 7 p.p.m.

P-G 2,400 p.p.m. P--G 10,Ooo p.p.m. p--G 6,000 p.p.m. P--G

Dolomites “Carbonates”

p--G 7 p.p.m.

‘Tnsolubles” Clays “Heavies” Organic matter Bitumen

P--G

TI

Tm

U

V

W

Y

PG,B

PG

P--G

P--G

p.p.m. P-G 5 p.p.m.

p.p.m. P-G 160 p.p.m. P--G 3,000 p.p.m.

1,500

P--G I p.p.m.

P--G

PG

P-G P--G

PG P-G

P--G

P-G

p.p.m.

p.p.m. s-V,FM 2 - 10-5 g/g d.m.

150

Algae

p-v

s-v

9.2. 10--3 p-v

%

of ash

Phaeophyceae Rhodophyceae Chlorophyceae Corallinaceae

5,350

0.7p.p.m. 13 p.p.m.

P-G

0.0001% Ye03 P - G 80 p.p.m.

YtJ

Zn

Zr

p.p.m.

E3

200

CI 0

PG 700

F

PG

p.p.m. P--G 500 p.p.m. P-G

P--G 340 p.p.m. P--G P-G P--G

250

s-V,FM 4.10-8 g/g d.m.

M

6

Ei

8

8cn

1 $

p-v

z

+

P-V

CI

:s 2

cn

P--G

0.4 p.p.m.

P--G 4 p.p.m.

0.5 p.p.m. p-V

P-v

h-TG

Bryozoa Protozoa Foraminifera “Globigerina

ooze”

P--G

P-HS 0.01 % P--G

p.p.m.

p.p.m.

0.15 -

Footnote is given on p.49

h-S 0.01 %

P-G

10 p,p.m.

1,500

_____

P-v

<0.001%

P--G 180

p.p.m.

P--G (in insolubles)

--___

P 4

> l a

> I a

> I a

I

a m

I C ? W

cq%

>> I I aa

a

l

>

K. H. WOLF, G. V. CHILINGAR A N D F. W. BEALES

x

.o

78 E a0

I

x am

I . a

>El Ej

Echinodermata Echinoidea Crinoidea Annelida

h-V

S,h-V

h-V

h-G h-G 1 . lo-'% 4.8 p.p.m. d. wt. d. wt.

h-TG 0.18 p.p.m.

0.123 % d.m. h-G 5 p.p.m. d. wt.

s,h-V 0.018% d.m. h-G I6 p.p.m. d. wt. s,h-V,G 12 p.p.m.

m

z

B r

8

5 8

3z

'Distribution of elements in carbonate skeletons, rocks and associated components as based on a literature survey. In cases where several values were available, the maximum value has been used. Future research will result in many changes of the data in Table 11, and many of the blank spaces E! are expected to be filled in. As only a number of selected publications were surveyed it is essential for those readers engaged in detailed studies to consult the original literature, p = present, but no other details given; s = present in soft parts of organisms; h = present in hard parts (= skeletal) of organisms; p.p.m.= parts per million; d.m.= in dry matter; I.m.= in living matter; d. wt.= dry weight; wt.= weight; gig= gram per gram; B= (1936); F M = FUKAr and MEINKE (1962); G = G~~~(1960)+ompilation W BROECKER (1963); BT= BLACKMON and TODD(1959); E = VON ENGELHARDT of numerous publications; H = HOOPER(1964); K = KONISHI(1961); KB= KRINSLEY and BIERr (1959); P G = PILKEYand GOODELL (1963, 1964); c) > and HASKIN (1964); S1= SIEGEL(1965); TAI= TUREKIAN and ARMSTRONG(1961); P H = PILKEYand HOWER(1960); S= SAm (1951); SH= SCHOFIELD TAO= TUREKIAN and ARMSTRONG (1960); T G = TATSUMOTO and GOLDBERG (1959); V= VINOGRADOV (1953)&compilation. ~

$

2 *

6

0

z

5

9

TABLE 111 TRACE ELEMENTS IN CARBONATE ROCKS AS GWEN IN VARIOUS PUBLlCATIONS (IN PARTS PER MILLI0N)l

Elements

RANKAMA and SAHAMA

KRAUSKOPF RUNNELSand SCHLEICHEROSTROM(1957) ( 1955)

(1950)

Ag As Au

B Ba

Be

Br Cd C1

co Cr

cs

cu F Fe Ga Ge Hg

I In

K La

Li Mn

0.2

0.2(?)

0.005-0.009 3 120

0.005-0.009

0

200 0 2

20-200 <1

0.2-2

(1956)

range

average

0.1-20

0.9

5-300 10-3,OOO

21 390

range

1-200 10-10,OOO

average

18 260

5(?)

1-200

13

3-61

11

20.2 250

5-20

0.13-500

5

4-70

18

3.7

3(?)

n.1.

n.1.

3,200-46,OOO

11,300

0.03

0.03(?) n.1.

n.1.

300-7,500

1,600

20-6,OOO

850

400-3,700

1,400

0.02(?) 26 385

2-20(?)

-

GRAF(1960, table 38) average

GRAF(1960, table 19) range

average

< 14,OOO <5-8,OOO

320 220

< 5-35 t2-100

4.3&1.8 13

200-700

320

2.5+1.5 0.09 0.07 2.8

t3-10

2.2+1.2

14+11(?) 20*17 5W?)

<25-50 < 1-1,OOO

14&11 31

0.7 &0.4(?) 2.5 k1.q?) 0.005-0.009 12+ 8(?) 150f110 1

7 0.1-0.2(?) 460 4.3 9k4 4 +2 14&9 320

Mo Na Ni Pb Ra Rb Sb

sc

se. Sn

Sr Sr Sr Th Ti

0.14.5(?)

0.1-1 (?)

425-765 -800 Analyses with < 10%Mg0 Analyses with > lO%MgO 1.1 1.3 < 10

Y Zn Zr

0

44

n.1. 10 16

5 50

1-200

19

14->2,000

470

=

240-8 10

10-6,OOO

tr.-2,400

2-20( ?)

5-3.000

n.d.-tr.

4-20

0.5-500

35

-~

ln.1. = not listed; n.d. 2Four samples

n.d.-20 tr.-3,300 n.d.-70 6-100

1

700 15 26

0 t0.1

U

V W

3-10 5-10

0 5-10 0.42 . 10-6 0

0.1-70 n.1. 0.5-100 1-200

not determined; tr.

=

traces

n.d.-700

490

400

40

1.1 &0.7(?) 12f4

<5-60 < 10-80

11&1 7.2+4.2

7034 0.2 *o. I(?) 0.3(?) 0.1-l(?) 4

< 30-800

60511

8

475 f50 1.910.8 300+150(?) 2.1 *0.2 15f8(?) 0.5(?) 1318 26*5 1714

10,10,20,20 p.p.m.2 <10-6,000 < 10-6,OOO 1

m

420 484 134

<10-150

1213

<2&80

1318

< 10-200

16f3

52

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

COMPOSITION OF ORGANIC CONSTITUENTS AND SKELETAL LIMESTONES

A definite interdependence between chemical elements on one hand and living organisms on the other has been demonstrated; organic processes control and manipulate elements, and conversely, elements in the surrounding media influence both fauna and flora. Both the tissues or organic matrices and calcareous skeletons have revealed enrichment of elements that has proved to be of considerable theoretical and practical interest, or may do so in the future. Some of the elements are essential to the life processes, whereas others are taken up, so it seems according to our present state of knowledge, accidentally. Even post-humously, the organic material influences diagenetic processes as discussed later in this chapter. High concentrations of such constituents as zirconium, titanium, and thallium have been recorded. These observations are particularly striking in view of the fact that some of these elements have not yet been detected in sea water (GOLDBERG, 1957). According to VINOGRADOV (1953), elements that occur in sea water in

TABLE IV DISTRIBUTION OF ELEMENTS AS PERCENTAGE OF BODY WEIGHT OF ORGANISMS

(WEBBand FEARON, 1937; with additions by MASON,1958)' ~

Invariable

(%)

Variable

~

primary (60-1)

H C

N 0 P

_

secondary (1-0.05)

micro-constituents (<0.05)

Secondary

Na Mi3 S

B Fe Si

Ti V Br

c1

K Ca

Mn cu

I co Mo Zn

_

~ Micro-constituents

Li Be Al Cr F Ni Ge As Rb Sr

Contaminants

He A Se

AU Hg

Bi TI

Ag

Cd Sn cs Ba Pb Ra

'These authors pointed out that this classificationis by necessityarbitrary for some of the elements.

53

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

TABLE V CONTENT (%) OF ELEMENTS I N DRY ORGANIC MATTER OF MARINE ORGANISMS (DRY MATTER APPROXIMATELY 10% OF THE LIVING MATTER)

(After WEDEPOHL, 1964, table 8) 9 types of KALLE organisms, (1943) Gullrnarflord (Southwest Sweden) NODDACK and NODDACK (1939)

Fe

6.9.

Zn Mn

4.5- 10-2 1.2-

1 (Phytoplankton); 4 10-2 (Zooplankton) 2 . 10-2 2.10-3

v

8.5. 10-3

3 . 10-3

cu

3.0.10-3 2.1 * 1.3.

5.10-3

10-4

MO

1.1.10-3 8.2. 5* 3.3 * 10-4 3.10-4

co

2.1 10-4

Ni Pb

AS Sn Ti Ag

B C

1n.d.

-

10-1

5.10-5? 30

=

not determined.

Plankton VINOGRADOV (1953)

Algae Plankton Plankton BLACKand NICHOLLSFUKAI and MEINKE MITCHELLet al. (1959, 1962) (1952) (1959) and others

6.9 * 10-2 (Cyanophyceae) (Phyto1 (Peridiniaceae) plankton) 2-10-1 (Diatomaceae) 8 . 10-3 4.10-5 9.10-3 (Cyanophyceae) 4 . 5-5-2. 10-2 (Diatomaceae) 2.10-4 10-3 3.3. 10-2 (Cyanophyceae) 10-3 2.8. 3.7. 10-4 3 .10-3 8.4. 10-4 10-2 5 ' 10-2-10-'

2.5 . 10-4

5 . 10-5-2

* Pb: MALJUGA(1 939); 1.2 . 10-3 (microplankton): LAEVASTU and THOMPSON (I 956) 7.10-5

n.d.l 1.1 . 10-4 7.7. 10-4 3 . 10-3 4 10-4 3.10-5 3.9. 10-5 3.9. 10-4 8 * 10-5; (microplankton): SUGAWARA et al. (1961) 7. I . 10-5 9.5 10-4 9.4. 10-3 30 (Peridiniaceae, Cyanophyceae) 11-25 (Diatomaceae)

.

54

K. H. WOLF, G. V. CHlLlNGAR AND F. W. BEALES

amounts larger than are concentrated by organisms 10-100 times that amount. Some of the elements present in the ocean in quantities less than are also organically utilized. Radioactivity of lake plankton reaches 100 times the radioactivity of the water in Quirke Lake, Ontario. (1937) and gave MASON(1958) discussed the work of WEBBand FEARON updated information on the elements found in biological material which can be classified as structural elements (C, H, N, 0, P, S, C1, Na, K, F, Mg, Si, Ca) and biocatalysts (Fe, Cu, B, Mn, I). Table IV gives some idea on the elements present in organisms. (See also Table V.) When these data are plotted on the periodic table (see MASON,1958, fig.37) it becomes clear that these elements (except iodine) are invariably all of low atomic number. HUTCHINSON (1943) has shown that there is a relationship between the elements incorporated in organisms and ionic potential of the ions (see also MASON,1958, fig.38). It has been most difficult to prepare a summary of representative data on trace elements of carbonate material for various reasons. In many cases IIO clear distinction has been given in the literature on whether the analyses were carried out on either the calcareous skeletal parts, or the organic tissue, or both. Frequently, no indication has been offered to what extent contaminations and adsorbed components may have contributed to the trace-element composition. In precise studies, bulk compositions of organisms and carbonate sediments are of little use except in giving some rough estimations. The tables given here must, therefore, be considered only as an approximate guide. This is particularly true because only one, two or three specimens were analyzed in a number of cases. The manifold factors that determine the composition of carbonate skeletons and skeletal limestones are considered further under the following headings: ( I ) indirect and direct organic influences; (2) aragonite versus calcite, and other skeletal minerals; (3) magnesium in skeletons; ( 4 ) strontium content of skeletons; (5) other elements in skeletal and protective structures of organisms; (6) organic matter associated with carbonates; (7) direct bacterial influences. A number of other factors are discussed in the section on the application of composition to geological problems. Indirect and direct organic influences

Although details on the direct versus the indirect influences of life processes are given in various sections, the discrimination between them is of the utmost importance and warrants special attention. Where recognizable calcareous skeletons form the major part of carbonate sediments, the direct contribut,ionof organisms is readily apparent. On the other hand, it may be problematic, if not impossible, to estimate the contribution of the tissues of organisms to the trace-element composition of carbonate sediments. Even less clear are the indirect influences of. for example, algal and bacterial processes. It is the contention of most workers that

55

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

organisms are the major contributors to the formation of limestones. It is entirely possible that no carbonates were deposited prior to the origin of life very early in Precambrian time, and that subsequent to that time organic influences have dominated the global COz-carbonate budget. Element extraction and utilization within any environment of carbonate deposition will, therefore, have been subject to this overriding control. Among the non-calcareous Algae (i.e., those that do not form a carbonate skeleton), some can cause chemical changes in the water medium that results in “inorganic” precipitation of carbonates. ALDERMAN and SKINNER (1957) stated: “Our observations have shown that carbonate precipitation can take place in TABLE VI DIS’I?(IBUTION OF SKELETAL MINERAL SPECIES ACCORDING TO PHYLUM

(After LOWENSTAM, 1963, fig.2; see also CHAVE, 1962, for a table on mineralogic composition of skeletons; and for bacterial products see VINOGRADOV, 1953, and GREENFIELD, 1963)

Carbonates Aragonite Calcite Aragonite plus calcite “Amorphous” Silicates “Opaline”

? ? ? ?

+ + + + + + + + + + + + + + + + + + + ? + + + + + + + +

+ + +

Phosphates Hydroxyapatite Undefined plus calcite

+

Oxides Magnetite Goethite Magnetite plus goethite Amorphous (Fe) plus aragonite Surfates Celestite Barite

?

+ ++ +,

+ T

+ +

+

?

-I-

56

K. H. WOLF, G . V. CHILINGAR AND F. W. BEALES

waters which have only half the salinity of average sea water. Precipitation of carbonates in such solutions could be brought about by a rise in pH. The presence of vigorous plant life in water can have a very considerable effect on the pH of the solution.. extraction of C02 from lake water by plants during photosynthesis can raise the pH to 9.3 in strong sun-light. The pH may fall to below 8 at night as the water absorbs C02 from the air." Many ancient stromatolites, probably formed by Algae, are not thought to be the product of direct inorganic and/or organic precipitation of calcium carbonate, but to have been produced by the binding of fine calcareous (and other) debris by algal filaments and cells. Whatever the derivation of the calcareous detritus may be, the metabolic algal processes will result in enrichment and/or depletion of the chemical elements in the associated debris. The originally inherited composition of the bound particles will, therefore, change. This complex picture is further complicated by the presence of Bacteria that utilize the algal tissue as nutrient.

.

'I

m 0 0 0 .I:

c

m

S

I

I

P ?

P

0

I

P

P

3 r

3

Fig. 1 . Time-stratigraphic distribution of silica (S)- and phosphate (P)-secreting organisms. Width of bars indicates relative importance of groups. (After LOWENSTAM, 1963, fig.10; by permission of University of Chicago Press, Chicago, Ill.)

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

57

Fig.2. Time-stratigraphic distribution of important carbonate-secreting organisms. Width of bars indicates relative importance as contributors to sediment. C=calcite; A =aragonite. (After LOWENSTAM, 1963, fig.12; by permission of University of Chicago Press, Chicago, Ill.)

Aragonite versus calcite, and other skeletal minerals

Calcareous skeletal parts are composed mainly of aragonite and/or calcite. As these polymorphs reflect biological and environmental factors, and because the crystal lattice of each determines the type of elements present and the degree of substitution for Ca, polymorphism must be given due consideration in the study of chemical composition. The following four major mineralogic groups can be recognized: high-Sr and low-Sr aragonite, and high-Mg and low-Mg calcite. In recent calcareous material vaterite may also be present. (See INGERSON,1962, for an excellent review.) Fig.1 and Table VI, based on findings of LowENsTAM (-1963),illustrate that in addition to the various forms of calcium carbonate some skeletons contain silica, phosphate, iron oxide, and sulfate. These non-carbonate components are not only of significancethemselves, but may also be important as adsorbants of trace elements. The approximate geologic ranges of the important calcite- and/or aragonitesecreting organisms are given in Fig.2. Most of the aragonite and high-Mg calcite that formed part of the Paleozoic and younger limestones have inverted to calcite. The factors determining the predominance of aragonite over calcite are numerous and complex. LOWENSTAM (1954a, b, 1963) has paid particular attention to the

58

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

temperature-dependence of the aragonite/calcite ratio. LOWENSTAM (1954a) divided organisms secreting calcareous shells into four types: (I) orders composed of forms that secrete skeletons entirely of aragonite, but in which the number of species is markedly greater in the warmer than in the colder water; (2) classes or subclasses in which all species of a given order secrete either all calcite or all aragonite, but in which the orders with aragonite-depositing species are confined to the warmer waters; (3) a transitionary type from type 2, containing species which differ from those in category 2 in that they secrete trace amounts of calcite in the colder climates, in their marginal geographic ranges; and ( 4 ) genera with species the skeletons of which are composed of mixtures of both aragonite and calcite, with the aragonite content increasing with higher temperatures and the calcite with lower temperatures, the temperature effect depending upon the species. The “species effect” is particularly marked in the mollusca. Their mineralogic composition and their temperature responses differ distinctly from genus to genus, and also within genera from species to species. In some organisms the aragonite, for example, is confined to particular localities in the skeleton. STENZEL (1963) reported on oysters that are mainly composed of conchilin and calcite, and have five small, but distinct, areas composed of aragonite (the resilium and four muscle pads). Of particular interest are the observations made by WATABE and WILBUR (1960) who performed both in vivo and in vitro experiments with organic matter. They demonstrated that the precipitation of aragonite versus calcite in molluscs is determined by the protein matrix. In a subsequent study, WILBURand WATABE (1963) found that the crystal growth and formation of organix matrix of shells takes place from a thin layer of extrapallial fluid enclosed between the mantle and inner shell surface. “Composition of this fluid presumably affects the submicroscopic pattern of the matrix which in turn influences the polymorphic type of CaC03 crystals deposited upon it. In vitro experiments have demonstrated that aragonite formation is favored by appropriate concentrations of inorganic ions and certain amino acids and that vaterite is favored by amino acids and glycoprotein (Y. Kitano, personal communication). Temperature had a marked effect on the ratio of CaC03 polymorphs. In regenerating Viviparus shell and in one strain of Coccolithus, vaterite was deposited in relatively high proportion at lower temperatures, whereas at higher temperatures vaterite decreased and aragonite increased.” Nitrogen deficiency had two effects on Coccolithus (an alga): (I) one strain formed plates of CaC03, although it formed no plates in normal medium, and (2) another strain deposited very considerable amounts of vaterite, aragonite and calcite in a nitrogen-deficient medium, whereas under normal conditions only calcite was deposited (see also W. D. EVANS,1964). Similar complexities have been pointed out by SIMKISS (1964), who stated that calcite, aragonite, and vaterite have been found in certain specimens of molluscs and marine Algae (i.e., coccolithophorids). The foregoing examples illustrate the control of the organic matrix, both in vivo and post-mortem, on the polymorphism of calcium carbonate. To what

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

59

extent it influences in turn the minor and trace-element contents is not known in precise terms. CHAVE(1954a) observed that different parts of the same specimen of an organism, despite being composed wholly of either calcite (e.g., echinoids) or aragonite, may vary in composition. This may well be a reflection of different composition within the organic matrix.

Magnesium in skeletons In his monograph on the elemental chemical composition of organisms, VINOGRADOV (1953) pointed out that one can recognize three groups of similar calcitic skeletons: ( 1 ) those with a small MgCOs content (Cirripedia, Mollusca); (2) those with a labile amount (Foraminifera, Bryozoa); and (3) those with continuously high MgC03 content (all Echinodermata, Corallinaceae, and Alcyonaria). Inasmuch as large MgC03 concentrations are found in skeletal calcium carbonate, especially in warm seas, Vinogradov suggested that the MgC03 precipitation is a secondary phenomenon and is more energetic when the ,Ca metabolism is more intensive. Vinogradov also pointed out that invertebrates with calcite skeletons that contain large quantities of MgC03 are typically marine organisms and are not present in fresh-water environments, e.g., Echinodermata, Alcyonaria, Calcarea and Corallinaceae. They are also absent in salt lakes such as the Caspian Sea; but some have been reported from the Red Sea and can withstand higher salinities than has been assumed hitherto. If organisms, such as the calcitic, Mg-containing Foraminifera, migrate into fresh water they lose their calcareous skeletons (with rare exceptions). Some invertebrates, upon adaptation to fresh-water conditions, lose Mg first of all from their marine “blood”. CHAW(1954a) found that, with the exception of a few cold-water calcitic forms, aragonitic skeletons are lower in Mg than the calcitic types, and that in all groups of calcitic organisms there is a linear or near linear relationship between the Mg content and the temperature (see also CHILINGAR, 1953, 1962a). CHAVE (1954a) also found that the total amount of Mg in skeletons decreases with an increase in phylogenetic level of the organisms. Although other factors, like salinity, depth of water, age or size of the individual organism, may be influential, Chave found little evidence of this. Subsequent research, however, led to modifications of the above generalized conclusions which are dealt with later in this chapter. CHAW(1954a) pointed out that the mineralogy of the organic skeletonsis complicated by the ability of some organisms to secrete both calcite and aragonite. As aragonitic forms seldom contain more than 1 % of MgC03, whereas the calcitic types rarely have less than 1 % MgC03 and in some cases up to 20-30%, the bulk composition of an organic skeleton depends to a large degree on the aragonite/ calcite ratio. This can be shown, for example, in the case of gastropods and pelecypods in which the presence of a few percent of calcite results in a distinct increase in Mg content. A similar relationship occurs in the annelids in which serpulid tubes are composed of calcite, aragonite, or a mixture of the two. The aragonite content

60

K. H.

WOLF,

G. V. CHlLlKGAR AND F. W. BEALES

increases with increasing temperature (LOWENSTAM, 1954b). Hence, the Mg content of the whole tube increases with higher environmental temperatures to a certain point due to the increase of Mg content in the calcite portion of the tube. The Mg content then decreases as the amount of aragonite becomes large, although the Mg proportion in the calcite continues to rise with the higher water temperature. CHAVE ( I 954a, b) cited an example of a Serpula tube composed of 70 % calcite and 30 % aragonite, with the former containing 13% of MgC03 and the latter less than 1 %. The bulk analysis showed approximately 9.4 % MgC03. Other complicating factors can only be evaluated by future research. For example, CHAVE (1954a, b) noticed that in the case of calcitic Algae, the correlation between water temperature and the Mg content is less perfect than in any of the other classes and phyla. This may be partly a reflection of the diverse taxonomic position of the Algae. Based on his observations, Chave concluded that the total Mg content is not characteristic of groups of organisms; however, the slopes of the temperature versus Mg-content curves are characteristic for different groups. Although this may be the case in some phyla, more recent studies have shown that both the ratios of the CaC03 polymorphs and their compositions are not always a direct function of temperature. BLACKMON and TODD(1959) showed that no combination of aragonite with calcite occurs in the Foraminifera, i.e., they are composed of either one or the other. This simplifies somewhat the consideration of bulk trace-element variations. It was also found that: (I) certain genera were aragonitic in both arctic and tropical waters, (2) certain other genera were always calcitic irrespective of environment, and (3) both calcitic and aragonitic genera are present in the same habitat. It seems, therefore, that a phylogenetic control rather than physicochemical influences determines whether either calcite or aragonite is deposited. This in turn controls the amount of Mg that can be taken up. Competition and selection, however, will ultimately develop a stable organic community in which this phylogenetic control may be subordinate to the physicochemical background. Such considerations greatly complicate the interpretation of results. The Mg content in the calcitic shells of most Foraminifera falls into a low (0-5 mol%) or a high (10 mol% or higher) range, with very few skeletons being in the intermediate range. The results given in the tables by BLACKMON and TODD(1959) suggest that mainly phylogenetic factors influence the proportion of Mg in the shells. They found some evidence, however, that cold water has a noticeable effect on Mg content. The genera from normally high-Mg families existing in arctic or deep tropical waters show varying degrees of incorporation of Mg, but do not exhibit a fixed rate of decrease of Mg content with decrease in temperature. The rate varies with the different genera. Every specimen from a normally high-Mg group indicated some decrease in Mg content where the water temperature was below about 20°C. Significant is the fact that the converse is not true. Where low Mg content is normal for a group, higher temperatures do not tend to increase

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

61

the Mg content above 5 mol%. Also some families of Foraminifera provide evidence that there is some relationship between the thickness of the shell and the amount of Mg. The observations of TUREKIAN and ARMSTRONG (1960) that “molluscan genera, which have species with some calcite in the shell structure, are generally high in Mg, and this obtains even when a species of such a genus has no calcite in it at all”, strongly suggests that a generic control of Mg is more important than the aragonite/calcite ratio. They also concluded that in addition to Mg, Sr, and Ba, trace-element contents in recent molluscs appear to be controlled by phylogenetic factors, although this is obscured by individual differences. Contrary to the findings of CHAVE (1954a), TUREKIAN and ARMSTRONG (1961) reported that the snails as a group are higher in Mg content than the clams. (For additional data on relationship between the Mg content and temperature see the section on ecologic implications in this chapter.) An interesting correlation between elements was given by VINOCRADOV (1953), who stated that the greater the amount of phosphate in eunicid worms, brachiopods, Bryozoa, and Crustacea, for example, the higher is the Mg content. NEWELL and RIGBY(1957) reported that “it is well established that limestone outcrops between low and high water levels show enrichment of Mg, and this certainly is not limited to the shores of hypersaline seas . , . ; nor is there evidence that it is an effect of differential leaching of the more soluble calcium carbonate”. They also stated that on Andros Island of the Bahamas the oolitic limestone surfaces in the intertidal zone show a slight but persistent enrichment in Mg (3.99.4 % MgC03). This chemical composition is comparable to the (1) intertidal muds of Western Andros, (2) lime-muds of the fresh-water lakes (5.7-9.5 % MgCOs), (3) deep-sea ooze from the Tongue of the Ocean (5.4-7.2 % MgCOs), ( 4 ) mud polygons bound by blue-green algal filaments (5.2-19.4 % MgCOa), and (5) laminated limestones (6.9-8.3 % MgC03). The relatively high Mg content of all of the above sediments may be due to a similar cause. One common denominator of these Mgenriched sediments is the intimate association with blue-green Algae, which, according to NEWELL and RIGBY(1957), seem to extract magnesium carbonate from both fresh water and sea water. The role of Bacteria has been investigated by CARROLL and GREENFIELD (1963) who showed that “these organisms are capable of -concentrating calcium and magnesium up to 10 times that of an equivalent volume of sea water. . . the alkaline earths are partly adsorbed, partly hydrogen-bonded, and partly complexed in or on the bacterial cell envelope”. Strontium content of skeletons

Strontium is, next to Mg, the most important element that has attracted the attention of many research workers, and cpnsequently a considerable amount of

TABLE VII Sr/Ca RATIOS OF ORGANISM+ REVELLETHOMPSON and CHOW and FAIR-(1955: see GRAF,1960, BRIDGE table 3-14) (1957)

Marine Algae Chlorophyta (green) Phaeophyta (brown) Rhodophyta (red) Nemalionales Cryptonemiales (corallines) Chrysophyta (golden brown) Coccolithophores Protozoa Foraminifera Porifera Calcarea Coelenterata Hydrozoa Alcyonaria Coenothecalia (Heliopora) All others Zoantharia (Madreporaria)

14-16

ODUM(1950a, 19576) GRAF(1960, table 3-17) Average values

KULPet al. (1952) Culvert ODUM(1957)) (variousformations Formation (modern as old as Proterozoic) (Miocene) specimens)

calcitic Algae 3.96 aragonitic Algae 10.82 calcitic fresh-water Algae 0.52

0.1&1.80

(listed as Algae)

0.49-13.00

(listed as Algae)

n.d. n.d.

2.93-3.45

2.93-3.45(3.20)

p

n.d. 2.78-3.28

2.78-3.28(3.07)

littoral Foraminifera

2.30-3.34

2.30-3.3q2.99)

calcitic marine sponges 3.82

6.83-1 1.2 2.73-1 1.2(8.69) 2.64-7.57(4.04) 7.57 2.64-3.78 8.85-10.7

8.85-10.7(9.86)

2.07

aragonitic calcitic aragonitic

11.02 4.10 8.06

aragonitic

10.80

1.86-2.77

Corals 0.12-1.62 (0.22)

c

1.1-1 2.90 2.0-1 1.40

k

m m

E

Annelida Serpulidae Bryozoa Brachiopoda (Articulata) Echinodermata Crinoidea Asteroidea Ophiuroidea Echinoidea Holothuroidea Mollusca Amphineura Pelecypoda Pectinidae, Ostreidae, Anomiidae All others Gastropoda Scaphopoda Cephalopoda Arthropoda Cirripedia Crustacea (Decapoda) Crustacea (Ostracoda)

1.20-1.57

1.20-1.57(1.36)

aragonitic marine calcitic marine calcitic marine (Telotremata)

2.56 2.60-2.89 2.63-2.78 2.46-2.89

2.56 2.60-2.89(2.73) 2.63-2.78(2.69) 2.4&2.89(2.70) 2.72-2.78(2.74)

calcitic marine calcitic marine calcitic marine calcitic marine calcitic marine

3.38 3.71 3.47 3.06 2.60

7.32-9.35

7.32-9.25 (8.06) 1.01-2.98(1.85)

aragonitic marine aragonitic marine aragonitic fresh-water calcitic marine

9.01 2.63 0.87 1.65

3.86-8.24 3.868.24(5.87) 3.00-3.94 3.00-3.94(3.4 1)

3.10 3.96 1.81

12.00 0.36-0.78 (0.66) Inarticulata 4.75 0.21-0.22 0.20-0.80 (0.45)

v)

1.01-1.33 1.19-2.91 1.25-2.48 Prosobranchia 1.25-2.48( 1.68) Opisthobranchia 9-1 l(10) 2.35 2.35 3.74 3.74 3.77-5.28

3.77-5.28(4.45)

6.00-6.69

6.00-6.69(6.17)

n.d.

n.d.

1Atoms Sr/1,000 atoms Ca; n.d.

=

not determined.

m

El 0.81-2.95

1.6-7.4

0.2 1-3.6

5* z

-I

* c1

aragonitic fresh-water aragonitic marine aragonitic marine aragonitic marine calcitic marine

0.75 2.31 2.35 4.86 4.60

marine (calcite and amorphous CaC03) calcitic fresh-water

6.03 0.62

0.12-0.1 6 0.7-1 .OO (Belemnires) 1.7-2.5

1.8-3.5

0.02-6.74

3.8-3.9

2.00-2.32 3.874.70 0.62-7.30

6

P1 E

64

K. H.

WOLF,

G. V. CHILINGAR A N D F. W. BEALES

information is available concerning this element. Table VII, VIII and IX give the Sr/Ca ratios as based on some selected publications. KULPet al. (1 952) and ODUM (1957b), among others, stated that the Sr/Ca ratio in organisms primarily depends (I) on the Sr/Ca ratio in the water medium; (2) on the salinity; (3) on the phylogenetic factors; (4) on the temperature and crystal lattice (polymorphism), which are thought to be of secondary significance by some; and (5) on possible other, as yet poorly understood, influences. KULPet al. (1952) investigated a large number of fossil specimens from one horizon of the Miocene Calvert Formation. The 23 species collected represent 23 genera, all of which exist today. The investigation showed that the Sr contents of a particular Miocene genus are relatively constant. Also, the investigations of Kulp and his co-workers suggested that, except for certain individuals, the Sr proportion is quite constant within a class (Table VIII) ranging from the Cretaceous to the Recent. This agrees with ODUM’S(1950a) results on various other animal types. The results of KULPet al. (1952), however, did not show agreement when samples as old as the Proterozoic were included (Table VIIl). They also could not find annual trends in Sr precipitation by organisms. It seems that for a given environment the fossils have the same Sr/Ca ratio. On the other hand, other organisms are selective and some show enrichment in Sr content. Worm tubes, for example, exhibit a very much higher Sr/Ca ratio than do molluscs.

TABLE VIII RANGES OF

Sr/l,Oo Ca RATIOS IN SOME GASTROPODA AND PELECYPODA OF VARIOUS AGES

(After KULPet al., 1952) Sample

Gastropod Turritella

Various Gastropoda Various Pelecypoda

Cretaceous

1.67

Eocene

Miocene

Lower

Middle

Lower

Upper

2.01

1.60

1 .72 1.69

2.58

4.15

Variousformations (extending back to the Proterozoic)

Calvert Formation, Miocene

0.12-0.16

1.8-3.5

0.81-2.95

1.6-7.4

PIiocene

Recent

2.48

2.52

65

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

TABLE IX SUMMARY OF THE

Sr ABUNDANCE DATA IN CARBONATES

(After KULPet al., 1952; and others)

Average of 155 limestones Average of 40 limestones Range of 78 Paleozoic limestones Average of 78 Paleozoic limestones Range of 25 Paleozoic limestones Average of 25 Paleozoic limestones Average of 155 fossils from Calvert Formation (Miocene) Average of 103 uncrystallized fossils (Brachiopoda, Pelecypoda, Gastropoda Average (198) of all fossils studied (including many recrystallized) Deep-sea calcareous ooze Recent carbonates of North America

Reference

Sr/l,OOOCa

KULPet a]. (1952) ODUM(1950a) KULPet al. (1952) KULPet al. (1952) ODUM(1950a) ODUM(1950a)

0.71 1.21 0.1 1-3.90 0.76 0.3-1.4 0.9 3.10 2.76 1.88

TUREKIAN (1957) SIEGEL (1961)

2.8-ca.24.0 (Sr/Ca) 8.3-13.6

In contrast, BOWEN(1956) stated that the amount of Sr in recent corals is much greater than that in fossil corals. An approximate linear relationship exists between the Ca/Sr ratio and geological time as far back as the Devonian period; the results obtained for the Silurian period are anomalous. Bowen suggested that Sr has accumulated in sea water progressively. This interpretation, however, is opposed by many others working on the geochemistry of strontium. Again it is apparent that the interpretation of results is a complicated matter. It is reasonable to assume that modern aragonitic corals will lose Sr when the aragonite is recrystallized to calcite. Also, bearing in mind that numerous workers have considered that Paleozoic rugose corals secreted calcite skeletons, the results for the Silurian period may reflect taxonomic variations below the class level. Comparing the Sr contents of ancient samples with those from Miocene formations, KULPet al. (1952) obtained the distinct differences shown in Table VIII. The analyses of Recent and Pleistocene corals by SIEGEL(1960; in press) indicateaslightly lower value for average range of Sr content in Pleistocene specimens. To what extent secondary changes have influenced the compositions cannot be evaluated here and discussions on the related problems are to be found in the section on diagenesis. The influence on the Sr contents by the water medium, the effects of calcium carbonate polymorphism, and the phylogenetic level of the organisms are considered next, whereas discussion of influences of salinity and temperature is deferred to the section on paleontologic and ecologic implications.

66

K. H.

WOLF,

G. V. CHILINGAR AND F. W. BEALES

Composition of water medium in determining Sr content

It has been demonstrated by a number of investigators, and supported by tracer studies, that large quantities of Sr can be taken up in shells, and that the Sr/Ca ratios in the skeletons of animals and plants are almost directly related to the Sr/Ca ratio in the environment (see summary by ODUM,1950a, 1957b; KULPet al., 1952). Take-up of Sr is reduced relative to Ca, however, leading to a Sr/Ca ratio that is usually lower than the ratio determined for the environmental medium (see section on “Phylogenetic effects”, below). The extraction of Sr from the water medium may have a notable influence on the chemistry of shallow-water regions. LOWENSTAM (1954a) pointed out that Sr fixation is particularly high in aragonitic scleractinian corals and aragonite-secreting Algae on tropical reefs, and suggested that this is probably the cause of the relative Sr depletion of the waters in the vicinity of the reefs compared to temperate and arctic waters. The removal of Sr apparently occurs at a faster rate than the replenishment of Sr by mixing. Thus, the question comes to mind as to what degree Sr depletion occurs, and to what extent the depletion affects other organisms and the trace-element content of inorganic carbonates in the vicinity of the reefs. Calcium carbonate polymorphism aflecting the Sr content

ODUM (1957b) stated that questions pertaining to the relationship between organic carbonate polymorphs and the Sr content are largely unsettled, for in some cases aragonite of fresh-water mollusc shells may have much less Sr than calcite skeletons of marine species. ODUM(1957b) concluded, therefore, that although on the statistical average one finds more Sr associated with the aragonite crystal lattice than with calcite, in any particular sample other factors are also operative. KULPet al. (1952) also pointed out that the crystal form is only a secondary factor. Nevertheless, some very general trends are obvious as indicated in Table X. Phylogenetic eflects which determine the Sr content

A number of observations seem to suggest that the “species”, “generic”, or “phylogenetic” effect, as it is variously called, is a major, if not the most important, controlling factor determining the Sr content in organic calcium carbonate as pointed out by TUREKIAN and ARMSTRONG (1960), among others. For example, in general the Sr content varies greatly in aragonitic pelecypods. Although the Sr content in calcitic types is lower, the latter overlap with aragonitic clams having a low Sr content. This indicates the importance of generic control of test secretion in molluscs. Also, clams as a group have higher Sr content than snails. Turekian and Armstrong emphasized the “generic” effect on Sr concentration but recognized that this is often obscured by other causes.

67

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

TABLE X AVERAGE

Sr/Ca

ATOM RATIOS, TIMES

1000,

CONTRASTED FOR CALCITIC AND ARAGONITIC SKELETAL

MATERIALS

(After THOMPSON and CHOW,1955) Calcite (excluding aragonitic species)

Algae, Corallinaceae Protozoa, Foraminifera Porifera, Calcarea Coelenterata, Alcyonaria Arthropoda, Cirripedia Mollusca Pelecypoda Anomiidae Ostreidae Pectinidae Bryozoa, Ectoprocta Brachiopoda, Articulata Echinodermata

Calcite-aragonite mixtures (excluding completely calcitic species)

3.20 3.07 2.99 3.16 4.45 1.22 1.22 1.31 3.41 1.36 2.71

Aragonite (excluding calcitic species)

Mollusca Pelecypoda

1.94

Gastropoda Prosobranchia

1.68

Coelenterata Hydrozoa 9.49 Zoantharia 9.86 Mollusca Arnphineura 8.06 Gastropoda Nudibranchia 10 Scaphopoda 2.35 Cephalopoda 3.74

ODUM(1957b) showed that there is a distinct difference in Sr/Ca ratio of aragonitic pelecypods, gastropods and calcitic Algae, to name only a few, from fresh water in contrast to those from sea water. In some cases, the marine-water specimens have a higher value by a factor of six. The Sr/Ca ratio is not, therefore, a taxonomic constant for large groups, but the distribution pattern may nevertheless be a distinct taxonomic property (ODUM,1957b). Only where the external conditions are relatively constant, as in certain marine environments, are the Sr/Ca ratios predictable from the taxonomic position alone. In general, however, it is now established that some genera, families, orders, and phyla are characterized by a certain range of Sr/Ca ratio values. ODUM(l957b) suggested that in addition to tissue and mineralogical food chain1 differences it appears that some other factors appear to be operative in controlling, for example, the high Sr/Ca ratio in reef corals and low ratio in pelagic Foraminifera, pelecypods and brachiopods. Odum stated in his section on Srturnover and isolation of depositional surfaces, that a partial answer may be found in the same phenomenon inside organisms that may occur in the geochemical cycle of isolated environments. In both cases, the precipitation of Sr-poor calcium 'Different organisms use different types of food from which they extract different trace elements to build their tissue and skeletons.

68

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

carbonate will increase the Sr/Ca ratio in the surrounding depositional medium. In regard to organisms, ODUM(1957b, p.65) stated: “The exclusion of Sr from the crystal deposition tends to raise the Sr/Ca ratio in the surrounding tissues. If deposition takes place under a steady state condition which involves little free ionic exchange with the external medium, the Sr/Ca ratio will be higher both in the tissues immediately around the deposition and in the deposition itself. If there is free exchange with the environment, the Sr/Ca ratio of the immediate chemical environment of the deposition will be little altered by the deposition and a steady state condition will result with the lower Sr/Ca ratio both in deposition and surrounding tissue. Rapid deposition or slow exchange will tend to raise the Sr/Ca of tissue as noticed by SWAN(1956). Rapid circulatory systems, efficient excretory systems, and planktonic existences, all tend to lower the Sr/Ca ratio by this prediction. On the other hand, deposition in enclosed places deep in tissues not closely connected with exchange membranes will lead to higher Sr/Ca ratios.” The experimental graph (Fig.3) drawn by ODUM(1957a) appears to support the “exchange theory” that controls the Sr/Ca ratio.

t

Sr/Ca

Atoms per 1000 atoms

E 3

2

s

._ L

Kidnev strbng

4

Moderate

:.

Weak

U

,“ L

*

Flamecells

c m Diffusion

t

Planktonic Currents Sessile None

Separation of calcification surface f r o m exchange with thesea

Fig.3. A semi-quantitative graph relating the Sr/Ca ratio of skeletons of various groups of organisms to the rate of turnover of substances in the depositional tissue. The vertical coordinate: the strength of the excretory and circulatory systems of the organism ranging from no circulation to a strong kidney. The horizontal axis: the thickness of the tissue separating the calcification surface from the sea. An effort has been made to draw isopleths of approximately equal Sr/Ca ratio. Species with poor exchange due to poor circulation and thick separation from the sea in the lower left corner of the diagram seem to have higher Sr/Ca ratios. Species with exposed calcification surfaces and good circulation provided either internally or due to planktonic existence are presented in the upper right side of the diagram, and are characterized by lower Sr/Ca ratios. (After ODUM, 1957a, fig.2; by permission of the Institute of Marine Sciences, Texas University.)

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

69

LIKINS et al. (1963) performed interesting experiments that demonstrated the difference between the vital (= organic, metabolic) and non-vital (e.g., physicochemical surface exchange) uptake of strontium into aragonite. The experiments were performed on the ( I ) living fresh-water snail (Australorbis glubrutus) with aragonitic shell; both the pre-test (= preformed) shell and newly, metabolically deposited shell material (precipitation was induced by removing some of the original shell) were tested; (2) aragonitic shell (snail-free) of a dead snail, and powdered shell material of the same snail; and (3)artificially precipitated aragonite and calcite. On exposing these three groups of materials to a number of solutions with varying concentrations of strontium and calcium, LIKINSet al. ( I 963, p.276) concluded from the results that there is a " . . . marked discrimination against strontium relative to calcium in new shell formation which decreases as the Sr/Ca ratio of the solution was increased. Preformed shell also discriminated against Sr but to a lesser extent. Conversely, snail-free shell took up Sr preferentially as did powdered shell in an in vitro exchange study. Aragonite and calcite precipitated from calcium solutions containing S9Sr and 45Ca removed equal proportions of these two isotopes." Apparently, the discrimination against Sr relative to Ca in the living snail is primarily the result of metabolic process with the possibility of some crystallographic differentiation; whereas in the case of dead snail there is mainly an exchange of ions between the solution and the shell material, possibly accompanied by a small degree of recrystallization or inversion (LIKINS et al., 1963, pp.276-277). In his work on the relationship between Sr, Mg, and lgO/l60 ratios, LOWENSTAM (1961, 1963) found that the brachiopods investigated by him show a discrimination against Sr and Mg, and that the means of Sr/Ca and Mg/Ca ratios of shell material are significantly lower in contrast to those of sea water. Other jiuctors influencing the Sr content

In addition to the factors mentioned above, some others may also be influential. Although they may be insignificant in general, in individual cases they can contribute to cause distinct deviations from the norm. For example, KULPet al. (1952) suggested that the high Sr content of Lingulepis is probably related to the high proportion of phosphatic material in the shell. Considering the bulk compositions of skeletal limestones, the amounts and types of non-carbonate contaminations may become important factors in controlling the trace-element compositon. HIRST(1962) illustrated that the Sr/Ca curves of some of the Recent sediments indicate that the Sr is more concentrated in those containing considerable amounts of aragonitic skeletons. On relating the Sr/Ca ratio to the percentage of Ca, additional control on Sr content was suggested: probably, adsorption by clay minerals.

70

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

Sr content of skeletons versus sedimentary matrix of limestones

An interesting relationship was found by KULPet al. (1952) between the matrix and the skeletons. Most striking is the higher Sr content of the fossil than that of the carbonate matrix. The average values of Sr/l,OOO Ca ratios for the skeletons and the matrices are 1.03 and 0.51 respectively, which gives a ratio of approximately 2/1. KULPet al. (1952) examined fossil brachiopods and matrices from a common horizon to check on any possible relative variabilities. They found, however, that the Sr concentration of brachiopods remained constant despite the variable contents of Sr in the matrix samples. The Sr concentration of the matrix may be controlled partly by the proportions of skeletal fragments and inorganic carbonate, and partly by the type of skeletons in the organic fraction. It does not follow, however, that where the fossil and matrix show the same Sr content, the matrix is mainly skeletal and is composed largely of the same fossils that make up the framework. Original differences may well be reduced (or completely erased) by differential solution, recrystallization, replacement, or some other process. Other elements in skeletal and protective structures of organisms

In addition to Mg and Sr, a number of other minor and trace elements have been found in association with calcareous skeletons. WISEMAN (1964) stated that coccolithorphorids, for example, can concentrate nickel, cobalt, and copper, and do so to a greater extent than planktonic Foraminifera. In order to prevent contamination, utmost care should be taken in the preparation of the samples. Most interesting is the observation made by GRAYSON (1956) that while attempting to separate siliceous and calcareous material with hydrofluoric acid, the CaC03 of various components was replaced completely by calcium fluoride (CaF2) with preservation of all minute structural details. Changes in concentrations of trace elements accompanied this major transformation. EMILIANI (1955) spectrographically analyzed pelagic Foraminifera and found the presence of small amounts of Ti, Al, Si, Fe, Mn, Mg, and Sr. He discovered that when the analytic data was arranged in order of decreasing amounts of Al (on the assumption that this indicates decreasing sedimentary contamination of the samples), then Mg, Fe and A1203 reduced to zero simultaneously, whereas Si and Mn did not. This suggests that Mg and Fe are not part of the skeletal material, and that Si and Mn may be incorporated in the skeletons or tissues. As Emiliani pointed out, Si does not substitute for Ca and it is not clear, therefore, how it might be associated with the shell material. Although Mn can substitute for Ca, one has to consider the presence of possible surficial MnO2 crusts on the organic shells that cannot be easily removed by ordinary washing processes. According to Emiliani, the Sr content in the Foraminifera did not change with the change in Al content but remained constant, thus indicating that it is a part of calcium carbonate structure.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

71

Comparing regional changes, Emiliani stated that “the abundance of elements characteristic in terrigenous sediments (Ti, Al, Si) generally appears to be greatest in the Caribbean and least in the Pacific samples. The Pacific samples may have washed more cleanly, or perhaps these elements are less abundant there than in the Caribbean and the Atlantic. In either case, analyses may be arranged in order of decreasing amounts of A1 on the assumption that this indicates decreasing sedimentary contamination.” TUREKIAN and ARMSTRONG (1961) stated that the low Ba content in contemporary molluscan shells is a consequence of the low Baconcentration in theocean. Of the three elements, Sr, Ba, and Mg, the greatest variability in concentration is exhibited by Ba. The Ba content is on the whole higher in clams than it is in snails. “This may be explained in terms of the environment in which these two groups are most often associated. Snails to a large extent are epifauna while clams have a large component of infauna. The low content of Ba in the sea contrasted with its high content in marine muds and shales may provide the difference in environment of shell growth of clams and snails. . . ” As ODUM(1957b) pointed out, especially mud-eating organisms may take up elements from the sediments during digestive processes. Comparatively high values of uranium in corals (2.9-5.5 p.p.m.) have been mentioned by TATSUMOTO and GOLDBERG (1959). In contrast to Sr, for example, which is more readily accommodated in aragonite as compared to calcite in biological specimens, uranium in the limited cases studied does not show any evident preference apart from that noted in the case of corals. GOREAU (1961) developed a technique of measuring growth of living corals by introducing a radioactive 45Ca tracer into their skeletons. Organic matter associated with carbonates

The control of organic matter and matrices on the minor and trace elements ranges from subordinate to very considerable. W. D. EVANS(1964) stated, as have others previous to him, that organic matter may affect diagenetic processes such as solution, reprecipitation, recrystallization, and so forth, of both carbonate and other minerals. LONGet al. (1963) discussed the significance of organic materials in sediments as a possible useful indicator in paleogeographic reconstructions in oil (1962) supplied the following data on the proportions of exploration. GEHMAN organic matter: (I) mean organic content of limestones = 0.24%, (2) mean organic content of shales = 1.14%, (3) mean hydrocarbon content of limestones = 98 p.p.m., and (4) mean hydrocarbon content of shales == 96 p.p.m. Gehman also pointed out that Recent limestones have higher contents of organic matter than ancient sediments. Reference such as the above to organic matter in sediments is common, and its influence on diagenetic events is probably great. For example, the decomposition

72

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

of organic matter may free associated cations. BERGER (1950) offered the following division concerning the role of organic matter (see also OPPENHEIMER, 1960): (A) Concentration of elements through metabolic processes: C, N?, P, S, Fe, Si, Ca, Ba, Mn, I, (Cu, V, geochemically not active) Zn? ( B ) Post-mortem concentration: (1) Chemical. (a) Uptake into organic molecules: V, Ga, Ge? (b) Sulfide precipitation: Fe, Cu, Pb, Zn, etc. (c) Reduction: Ag. (2) Physical adsorption: V, Ag, Th, U, etc. The survey by ABELSON (1 957) showed the widespread presence of proteins in Recent skeletons, which makes it likely that many, if not most, fossils originally contained some proteins. Abelson exposed different layers in Recent shells by removing successive laminae with dilute acid, and thus determined the location of the protein within the skeletons. He found that many of the shells are sufficiently dense to make the interior impervious to Bacteria, which suggests that preservation of proteins in fossils may be possible. Many fossil specimens have been reported to contain amino acids which may be partly adsorbed on carbonate skeletons. ABELSON’S (1 957) experiments indicated that aspartic and glutamic acids are the two amino acids which are readily adsorbed, whereas alanine, one of the principal amino-acid camponents of fossils, has almost no affinity for CaC03. This suggests that at least the latter is not merely a contaminant adsorbed to the carbonate skeletons. ABELSON (1959a, b) also reported that porphyrins are among the most stable organic materials and, therefore, can be expected to be found in ancient specimens. Very little is known on the history of various metals originally contained in or adsorbed on the soft tissue of organisms as mentioned by GRAF(1960), who gave a list of pertaining references. GLAGOLEVA (1961) investigated the role of bottom organisms in contributing the trace elements and concluded that some elements came from the calcareous skeletons, whereas others must have come from some other source, possibly from the soft organic parts. Glagoleva did not, however, support the latter possibility by conclusive evidence. HOODet al. (1959, in: INGERSON, 1962) identified carbamino-carboxylic acid complexes which are utilized, for example, by certain marine phytoplanktons in photosynthesis. These compounds may complex Ca, Sr, and possibly Mg into non-ionic form. According to ABELSON (1959a,b), hemalin and chlorophyll (porphyrin pigments) readily lose their Fe and Mg to become free of metals until V and Ni occupy the sites formerly held by Fe and Mg. The resulting stable complexes are hydrophobic and very soluble in petroleum; and are the types of porphyrins commonly found in sediments and petroleum. (See GRAF,1960, parts I1 and 111 for literature survey.) GOLDBERG (1957) pointed out that parallelism in biochemical and paleobiochemical paths of trace constituents is difficult to establish, inasmuch as only

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very seldom analyses have been made on more than a few elements. In general, however, it has been found that the concentration of heavy metals is greater in marine organisms than that found in the hydrosphere. Also, it appears that organisms of lower phylogenetic levels seem to take up trace metals to a greater extent than do the vertebrates. The differences between the concentration of elements in organisms and in sea water exist for families as well as species, and the trace metals are retained by fairly strong chemical bonds in the organisms. GOLDBERG (1957) stated that “in general the relative concentration factors for metals in the marine biosphere as compared to sea water closely parallel the order of stability of metal ions with organic ligands”. SCHUBERT (1954) showed that for a variety of bivalent transition metals (essentially independent of whether the metals are attached to oxygen, nitrogen or sulfur atoms) the decreasing order of stability of the complexes is: Pd> C u > Ni> Pb> Co> Zn> C d > Mg. It appears, that the stability decreases as the basicity of the metal increases. Schubert also reported that for alkaline earth metals the order generally i s Z n s Mg, Ca> Sr> Ba> Ra, where position of Mg is often irregular. For certain tervalent metal ioas the sequence is often as follows: TI> Fe> G a > In> A12 Cr> Sc> rare earths. For the rare earths the order is Y > Sm> N d > Pr> La, again in the order of increasing basicity. In the case of group of divalent metal cations of the first transition series, the stability of complexes increases to a maximum (at copper) and then decreases: M n < Fe< C o < Ni< C u > Zn. It is of importance to remember that stability relationships may vary. For example, Mn2+ ions form stronger complexes with oxygen-type ligands, and Co2+, with nitrogen-type ligands; these differences are even more pronounced for c03+and Mn3+ ions 1954). (SCHUBERT, GOLDBERG (1957) mentioned that the fractionation factors (concentration in organism/concentration in sea water ratio) for sponges, for example, are as follows: Cu, 1,400; Ni, 420; Co, 50; Mg, 0.07; and Ca, 3.5. Biochemical fractionation can lead to an extensive depletion of some elements in the surrounding sea water as has been reported already for strontium in waters near coral reefs (SIEGEL,1960), and during extensive radio-yttrium ion concentration by red Algae and diatoms. Regarding the uptake of trace elements in connection with particulate matter by members of the marine biosphere, GOLDBERG (1957) mentioned that “these particles can enter the marine biosphere via the filter-feeding organisms and their predators, as well as by direct transfer through adhesion to the outer surfaces of plants and animals”. Because all these substances, except calcium carbonate, can exist as colloidally dispersed particles, it may be expected that the adsorbed ions with charges opposite to those of the colloidal particles will accompany them. LEHNINGER (1950) stated that the biological specificity of metal ions for such organic substances as proteins depends on: (I) the mass of the ions, (2) ionic charge, (3) ionic radius, (4) oxidation-reduction potentials of the ions, and (5) availability and chemical state of elements, among others.

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Certain enzymes have been found to contain Mn and facilitate the precipitation of calcium phosphate. INGERSON (1962) suggested that similar enzymes in lime-secreting organisms may be active in the deposition of calcium carbonate and possibly even of dolomite. In pursuing this problem the active metal in the enzymes should be of particular interest. INGERSON (1962) suggested that, although the available information is extremely scarce, the work of VINOGRADOV (1953) and others shows that certain groups of organisms are characterized by relatively high contents of certain elements. If high concentrations of particular elements, that are known not to precipitate inorganically, are present in carbonate sediments, it may indicate that the corresponding organisms were active in the formation of these sediments. Considerable caution is necessary in the selection and preparation of ancient sediments for analysis for traces of organic compounds. For example, during the preparation of insoluble residues, fungal hyphae, associated with lichens growing on the rock surface, have been observed to penetrate several inches into the rock. Freshly quarried material and diamond drill cores can be penetrated and contaminated rapidly. Direct bacterial influences

Diverse bacterial activity can hardly be overestimated in (I) the precipitation and solution of carbonates, (2) the transformation and decomposition of both inorganic and organic materials, (3) the control of the pH and Eh of the water medium, ( 4 ) the production of gases and disfiguration of sediments, and (5) the liberation and concentration of minor and trace elements. VINOGRADOV (1 953), ZOBELL(1957), OPPENHEIMER (1960), CLOUD (1962) and KUZNETSOV (1962) in numerous publications have given a list of bacterial processes and discussed their effects on the chemical composition of sediments. VINOGRADOV (1953) gave the following list of elements that are utilized or transformed by Bacteria: C, H, 0, N, P, As, S , Se, Fe, Mn, Al, Ca, Si, and Mg. Probably, future research will result in the addition of other elements to this list. The interesting phenomenon of Mg- and Ca-concentration mentioned by CARROLL(1963) has been presented earlier. This observation is of particular significance as it has been suggested that Bacteria may form a nucleus for calcium carbonate precipitation. TAFTand HARBAUGH (1 964) have suggested that the dark matter in the interior of some dolomite crystals in Recent carbonate deposits may be organic in composition. If one accepts the evidence given by LALOU(1957) and NEHERand ROHRER(1958), which indicates that Bacteria may be able to form dolomite, or at least carkact as nuclei for the inorganic precipitation of carbonates, then one may well suppose that the dark components described by Taft and Harbaugh could be of bacterial origin. The problems encountered by BROECKER (1963, p.2829) in evaluating the

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uranium series inequilibrium as a possible tool for absolute age determinations of marine carbonates, indicate that further studies of diagenetic processes, that may have been initiated and controlled by Bacteria, are of real practical importance. Application of skeletal mineralogy and chemical composition to geological problems

A number of attempts have been made to evaluate the possible use of the mineralogy and elemental composition of calcareous skeletons and organogenic limestones. Some of these possible uses are implied in the paragraphs which follow, in which brief consideration is given to skeletal growth and element uptake and retention, under differing ecological and diagenetic conditions. Mode and rate of shell growth and element uptake Experiments performed on the growth of calcareous shells have furnished some data on the mechanisms and rate of skeleton genesis, and on the role of chemical elements and certain isotopes. Some of the publications, such as the one by LIKINS et al. (1963), have been mentioned elsewhere in this chapter. Additional references are to be found in the chapter on techniques of analyzing carbonates by WOLF et al. (1967) in this book. T. F. GOREAU and N. I. GOREAU (1960) have used radioactive tracers to study skeleton formation in corals. Taxonomic significance In general, little information is available on significant mineralogical and chemical criteria in the classification of plants and animals as a whole. One exception is the attempt by BLACKMON and TODD(1959), mentioned earlier, who have suggested that the mineralogic composition of foraminiferan skeletons should be taken into account when lineages are under consideration. LOWENSTAM (1961) suggested that the discrimination of brachiopods against Sr and Mg, and the mean values of Sr/Ca and Mg/Ca ratios, may be characteristic for the species of various genera and orders of the articulate brachiopods. VINOGRADOV (1953) mentioned that skeletal chemical compositions in Algae, to name only one group, are characteristic for given species and genera and that composition is also related to the organism’s habitat. Mode and degree of diagenetic alterations The tempo of study of diagenetic modifications is increasing with development of more sophisticated techniques supporting the petrographic microscope, and making it possible to measure minute changes. The difficulties involved are, of course, enormous. Investigations on Recent skeletons, ooliths, pellets, various types of lime-muds, and so on, coupled with laboratory syntheses may eventually lead to the establishment of upper and lower limits of element concentration for skeletal and non-skeletal materials for particular conditions. Any increase or

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decrease from the “standard values” would indicate a change, and this in turn may assist in understanding diagenetic-epigenetic alterations. Temperature and salinity interpretations Many factors can influence the mineralogy and chemical composition of calcareous skeletons; however, most attention has been given t o the study of mineralogytemperature, magnesium-temperature, strontium-temperature, oxygen isotopetemperature, mineralogy-salinity, and strontium-salinity relationships, with lesser consideration of other interdependencies of elements within their environment of formation. These are briefly considered here: Mineralogy-temperature relationship. LOWENSTAM (1954a, b) has presented data that leave little doubt that temperature is one of the factors influencing skeletal mineralogy. Closer examination of small taxonomic groups, at the generic or specific level, however, revealed numerous exceptions. Lowenstam found, for example, that limited sensitivity to temperature of shell mineralogy and even a lack of mineralogy-temperature interdependence for some species appears to be linked to semi-terrestrial adaption. In some extreme cases, shell deposition was shown to occur only at elevated temperatures. In another case, Lowenstam reported on two species, occupying essentially the same environmental niche: one was found to be temperature dependent whereas the other was not. The mode of life may intervene as, for example, in the case of pelecypods where only the vagrant benthos show temperature-dependence, whereas sessile or cemented types do not seem to show it. Lowenstam also suggested that salinity may influence the aragonite and/or calcite precipitation of skeletons in addition to temperature and other possible controls. DODD(1961) stated that the mineralogy of the mussel, Mytilus caftforniunus, is not affected by temperature in small specimens, but larger ones show positive temperature-aragonite correlation. In the case of Mytifus edulis the mineralogy is also affected by salinity and shows a negative salinity-aragonite correlation. Dodd concluded, therefore, that Mytifus in the region investigated by him can be useful for paleotemperature and paleosalinity interpretations. Subsequent work by DODD(1962) showed that the shell of Mytifus calijornianus comprises four layers composed of either organic substance, calcite or aragonite. The growth-pattern and structure of some of the layers are believed to represent summer deposition and can be used, therefore, for age determinations of the shell. In turn, the growth rates, which are in part a function of temperature, can be determined; this provides additional paleotemperature data. In a more recent publication, DODD(1963a, b) suggested that a strong phylogenetic effect existed; different species of the same genus showed different temperature-mineralogy relationships which definitely indicate additional influences to those given above. Correlation exists between shell thickness and mineralogy in Mytifus cufifor-

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nianus, whereas mineralogy and shell length correlate in Mytilus edulis diegensis. Shell thickness itself, however, may not affect mineralogy; instead, some unknown factor may control both mineralogy and thickness of calcareous skeletons. Some species have an early stage in their growth that is temperature insensitive, whereas this is not found in other species. In some instances, Mytilus californianus smaller than 20 mm in length showed no relationship between mineralogy and temperature. Both subspecies of Mytilus edulis show negative correlation between salinity and aragonite content. This relationship is not determinable in the case of Mytilus calijornianus, as it is stenohaline in nature. In this connection it should be noted that, with one exception as reported by DODD(1 963b), all fresh-water molluscs are aragonitic. DODD(1963a) concluded that the variations in species and subspecies of Mytilus are not completely explained by any of the factors considered; as yet undetermined influences may be operative in controlling the aragonite content. It seems, however, that Mytilus californianus can be used for paleotemperature reconstructions, if large, complete, unworn, qnd well-preserved shells are used. Shell mineralogy of the two subspecies Mytilus edulis eduli and Mytilus edulis diegensis is possibly useful for paleosalinity determinations. Magnesium-temperature relationship. The magnesium content and the Mg/Ca ratio of calcareous shells certainly reflect environmental temperature as shown by CHAVE (1954a) and CHILINGAR (1953, 1962a). Deviations from the “ideal” temperature-magnesium relationship have been mentioned earlier in the section on magnesium in skeletons. Some other examples that show the degree of reliability of using Mg contents of skeletons for paleotemperature reconstructions are presented here. CHILINCAR (1962a) plotted the Ca/Mg ratios of various organic groups and confirmed CHAVE’S(l954a) observation that there is an inverse (hyperbolic) relationship between the Ca/Mg ratio and the environmental temperature. Chilingar found that in some cases temperature differences as small as 0.5”C are reflected in the Ca/Mg ratios of organisms. Artificially precipitated carbonates also showed an inverse relationship between the Ca/Mg ratios and the temperature. Chilingar, therefore, concluded that “the similarity in shape of ‘Ca/Mg ratio versus temperature’ curves of invertebrates and direct chemical precipitates suggests that the Ca/Mg ratios of these organisms are controlled to some extent by the effect of temperature on solubility products of CaC03, MgC03, Mg (OH)2, etc. The differences in magnitude of Ca/Mg ratio in different organisms may be related to the growth mechanism, and composition and pH of the body fluids.” DODD(1963a) mentioned that the Mg content of the outer calcitic layer of Mytilus increases with increasing environmental temperature, but not so regularly as does the Sr concentration. CHAVE(1954a) observed that the temperature-magnesium trend of a single echinoid species roughly parallels the trend of the entire class. PILKEY and HOWER

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Species trend

\

Class trend+

/’

L

4 -

Temperature

-

Fig.4. Diagrammatic illustration of temperature-magnesium trends of individual echinoid species and HOWER, as compared to temperature-magnesium trend of the whole class. (After PILKEY 1960; by permission of Journal of Geology.)

(1960), on the other hand, found that the trend of temperature versus MgCO3 content curve of a single echinoid species differs from the trend of the entire class: “the MgC03 content of a single echinoid species changes at a significantly lesser rate than the temperature-Mg trend of the entire class . . . ” They commented that future studies may reveal a step-like succession of temperature-Mg trends as shown in Fig.4. Based on their work, Pilkey and Hower pointed out that although LOWENSTAM (1954a, b) showed a positive correlation with water temperature for the articulate brachiopods at the class level, this relationship may not hold for the specific level of the brachiopods. In conclusion, there appears to be little doubt that in general CHAVE’S (1954a) and CHILINGAR’S (1953, 1962a) temperaturemagnesium correlation is valid but that in many particular instances the relationship has proved to be more complex. Both purely organic-metabolic and purely physicochemical influences appear to be operative, and more research is required on the species and subspecies level before paleotemperature reconstructions can be accepted as reliable. Strontium-temperature relationship. If one considers the observations made by LOWENSTAM (1 954a, b) that the aragonite/calcite ratio in many organisms increases with temperature, and that the Sr content is usually greater in aragonite, then one should expect a relationship between Sr content and temperature. In fact, Lowenstam did notice an increase in Sr content with increasing temperature in the Serpulidae. KULPet al. (1952) and ODUM(1950a, b) had previously reported, however, that no correlation, or at least a very poor one, exists between the Sr/Ca ratio and temperature even for those species the crystal form of which does not vary with temperature. Genera and species that have a wide range of temperature tolerance have similar Sr/Ca ratios in both warm and cold environments. For example, calcareous red Algae and aragonitic gastropods do not show a consistent

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variation pattern of Sr/Ca ratio with temperature in Odum’s table. KULP et al. (1952) and CHAVE (1954a, b) made similar observations; and the latter stated that the incorporation of Sr is quite different from the inclusion of Mg in echinoderms, for example. TUREKIAN (1957) analyzed Atlantic equatorial eupelagic cores for Ca and Sr and found that “when the Globigerina contribution to the Sr and Ca contents of the core are subtracted, a variation in the Sr-to-Ca ratio for the fine fraction is observed which is related to the Ericson temperature curve for the core-the high Sr/Ca ratio corresponding to a time of high surface ocean temperature.” This is best explained by a sympathetic variation in abundance of celestite tests secreted by acantharian Radiolaria. “If the carbonate and lutite sedimentation rates are sensibly constant, then Acantharia productivity is temperature dependent.” Subsequent investigations, however, seem to have shown that the celestite has been depositing at a constant rate and that the variations observed are due to varying rates of calcium carbonate deposition. PILKEY and HOWER (1960) found that Sr/Ca ratio is temperature dependent at the specific level but not at the class level. In a subsequent publication (PILKEY and HOWER,1961) they stated that Sr content of some aragonitic mollusc species exhibits a positive correlation with annual mean temperature; the Sr content of some calcitic molluscs shows a poor negative correlation with temperature but an excellent negative relationship with salinity. One species correlated poorly with all environmental factors examined. DODD(1963a) determined the Sr content of the calcitic prismatic layer of Mytilus and found that it is directly proportional to growth temperature, whereas the Sr content of the aragonite nacreous layer varies inversely with temperature. Combined study of Sr, Mg, and 0 isotope contents of skeletons. Many of the apparently contradictory results obtained in the study of carbonate chemistry and environmental reconstructions are due to the restriction of analytical investigations to only one or two components; and this, consequently, does not permit the detection of possible secondary modifications. LOWENSTAM (1961, 1963) reported investigations of the Sr and Mg contents and the 1 8 0 / l 6 0 ratios of Recent and fossil brachiopods. He demonstrated that SrC03 and MgC03 contents and 1 8 0 / 1 6 0 ratios of Recent brachiopods from waters having salinities close to the average of the oceans (33.5-36.5 %,) are all temperature-dependent. The data presented, however, suggest that the Sr and Mg contents in brachiopods vary not only with environmental temperatures but also with the species and other factors. The use of SrC03 and MgC03 contents in conjunction with l 8 0 / l 6 0 ratios for determining the presence and degree of diagenetic alterations are discussed in the appropriate section below. Other elements-environment relationships. PILKEY and GOODELL ( 1963) stated that

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aside from studies on Mg and Sr, only a few attempts have been made to evaluate the environment-element relationships for other major and trace constituents. They analyzed seven species of molluscs for Mg, Mn, Ba, Sr, and Fe contents and shell mineralogy, and studied their relationship to both temperature and salinity. The results indicated that no compositional variable is related to environmental temperature in four species. The Mg/Sr, Mn+Mg+Ba+Fe/Sr, and Mn+Mg+ Ba/Sr ratios, and the percentage of calcite correlate with temperature in three species, whereas other ratios or percentages exhibit a relationship in very few (two or less) instances. With two exceptions (i.e., Sr and calcite contents), the nature of the relationships between temperature and any single compositional variable are consistent and the correlations are always inverse or always direct. In general, however, the correlations with temperature are weak, and the differences in salinity cause greater changes in the composition of skeletons than differences in temperature. Thus, PILKEYand GOODELL(1963) concluded that the environment-composition relationships are too weakly defined to be of use in ecological reconstructions in the cases investigated by them. Relationship bet ween salinity cind skeleton composition. TUREKIAN (1955) pointed out that the importance of salinity as a possible independent variable controlling the Sr/Ca ratio in shells and sediments has not been stressed. KULPet al. (1952) also stated that the primary factor controlling the composition is the Sr/Ca ratio in the water medium, which in turn is related to salinity. The effect of temperature, according to them, is only of very minor importance. SAID(1951) reported on a species that was found to have a different skeleton composition in two widely separated localities, both in respect to elements present and the quantities thereof. Amphistegina radiata from the Red Sea has higher contents of practically all the rare chemical elements present than those of the Pacific Ocean specimens. The Red Sea specimens also have tin, whereas those of the Pacific lack it. According to Said, these differences may be due to a higher salinity of the Red Sea, among other possible reasons. More recent investigations have shown that salinity certainly has a marked effect on both shell mineralogy and elemental composition, but the relationships once again are far from being simple (PILKEYand HOWER,1960), as illustrated here by a few examples. PILKEY and GOODELL (1962) found that of several mollusc species some showed a positive correlation of Sr content with temperature, whereas others exhibited poor negative correlation with salinity. Except for one species, an inverse relationship between salinity and Sr content is present to some degree in all the molluscs studied. In a subsequent study, PILKEY and GOODELL (1963) demonstrated that the differences in salinity result in a greater modification of mollusc shell composition than do temperature variations, but that salinity concentration above 25z0 do not markedly affect the composition of the skeletons. Pilkey and Goodell showed,

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however, that salinity-composition interdependence is too weak to permit reliable paleoecological reconstructions. RUCKER and VALENTINE (1961) measured the concentrations of Mg, Sr, Mn, Na, Cu, and B in 71 shells of Recent Crassostrea virginica. They found that Mg+Sr and Mn contents are statistically inversely related to salinity. The Na content correlates directly with salinity; however, it is interpreted as not being part of the carbonate shell, and is thought instead to be present in interstitial salts deposited from sea water trapped in the skeleton. Contents of the other elements show no significant relation to either salinity or temperature. Rucker and Valentine concluded that the “multiple-regression technique based on the concentrations of Mn, Na and Mg+Sr permits the prediction of the environmental salinity of shell growth for Crassostrea virginica within a rather large standard error (5.3 %)”. DODD(1963a) reported a marked increase of Mg content in the outer calcitic prismatic layer of Mytilus with decreasing salinity. The Mg concentration in the aragonitic nacreous layer was too low for accurate measurements. Regarding the relationship of Ba and Sr to salinity, LANDERGREN and MANHEIM (1963) presented arguments showing that Ba is not a useful salinity indicator 8s based on our present knowledge, except possibly in rare cases. According to LEUTWEIN (1963), the Ba/Ca ratio increases in fresh water, whereas the Sr/Ca ratio decreases. Many exceptions to this rule, however, have been recorded. The excellent work by LOWENSTAM (1961, 1963), already mentioned in the section on temperature-element correlation, indicated that Sr and Mg contents of articulate brachiopods are partly related to temperature; however, other influences seem to be operative. Lowenstam, therefore, examined specimens from hypersaline and hyposaline environments and compared them with those of normal marine localities with similar water-corrected 1 8 0 / 1 6 0 ratios. It was found that the SrC03 contents and the Sr/Ca ratios of the skeletons are sensitive to changes in Sr concentration and Sr/Ca ratio of the water medium, and that the magnitude of changes differ for hyper- and hyposaline waters. Lowenstam also reported that in spite of proportional differences in Mg and Ca contents in hypo- and hypersaline waters, the uptake of Mg into brachiopod skeletons varies. He suggested that the absolute Mg concentration in the water medium is the important factor in determining the Mg content of the shells, but other influences are operative and complicate the relationship. ODUM(1957b) concluded that “ . . . it is possible to use analyses of Sr/Ca ratios to determine whether fossil skeletons that are unreplaced are marine or fresh-water . . If the Sr/Ca ratio is higher than the Sr/Ca of ocean species a nonmarine locality with a high Sr/Ca ratio can be recognized, but if the Sr/Ca ratios are close independent evidence is required for proper interpretation . . .” Inasmuch as closed lakes may resemble the oceans in having high Sr content, the Sr/Ca ratio cannot always indicate the difference between inland closed basins of sedimentary drainage and the ocean. In a table, ODUM(1957b, table 32) showed the

.

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use of Sr/Ca ratio in fossil skeletons for determining the nature of ancient environments. He recognized two groups: ( I ) fossils with high Sr/Ca ratio, which possibly indicate marine and arid lake origin, ground-water source, or volcanic drainage; and (2) fossils with a low Sr/Ca ratio which are indicative of origin in fresh water having a low Sr/Ca ratio. These two groups are so all-inclusive, however, that they are of little applicability in precise geochemical interpretations. Odum admitted that in controversial cases independent criteria have to be used, e.g., type of fossil assemblage. KUBLER (1962) investigated the Sr content of two sedimentary cycles composed of marine to lacustrine deposits and found a range of about 1,OOO to 5,000 p.p.m. He did not find a distinctive difference that could be attributed to the salinity factor. The foregoing considerations compel one to agree with ODUM(195713) that the Sr/Ca ratio is not a complete answer in salinity reconstructions; however, in many cases it can be helpful if used with other sources of evidence. The present state of our knowledge permits us to support other data useful in recognizing specific environments with information on the Sr/Ca ratios. These data may assist in attempts to interpret ancient environments but too little is known about Sr-Ca partition during genesis, or modification during diagenesis, to permit definitive interpretations based on Sr/Ca ratios alone. Skeleton-environment relationships, and “Law of Minimum in Ecology and Geochemistry”. Some insight has been gained into the factors that control directly and indirectly, separately and in combination, the mineralogic and elemental composition of the calcareous skeletons of both plants and animals: carbonate polymorphism, temperature, salinity, phylogenetic level, growth rate of shells, multimineralogic composition, seasonal and life-span variations in composition and mode of development, biochemistry of body fluids, adsorbed and absorbed impurities, solubility products and other conditions in the depositional medium, non-uniform degree of effects with changing physic0 chemical conditions (e.g., salinity effects are absent in some cases above 25%,, but are distinct below that value), mode of life (e.g., planktonic versus benthonic; crawlers versus borers and burrowers), mode of food-intake, and many others. The published results so far indicate that if the composition of skeletons is to be used for definite paleoecological reconstructions, it can be done with confidence only at the specific level. One promising approach is suggested by the work of PILKEY and GOODELL (1962) who found that certain species of molluscs are either temperature- or salinity-insensitive to varying degrees. By the simultaneous use of shells of more than one of these species, it may be possible to make both paleotemperature and paleosalinity interpretations. Wherever possible, shells composed of either calcite or aragonite should be utilized to eliminate complex

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effects due to polymorphism. More than one variable should be determined in large samples to enhance the reliability of the interpretations made. With an increase in the data on environment-organism and environmentmineral relationships, the familiar Law of Minimum in Ecology may be expanded to include minor and trace elements, and inorganically and organically formed minerals, and be designated instead The Law of Minimum in Ecology and Geochemistry (WOLF,1963b). Briefly stated, the geochemical phenomena that are sensitive to environmental conditions can be used in conjunction with biological data as criteria to narrow down environmental ranges. WOLF(1965a) demonstrated the partial application of this principle to a Devonian reef study. Environmental reconstructions of regional trends in skeletal mineralogy and chemical composition Regional trends in both the mineralogy and chemical composition of skeletal carbonate sediments have been shown by CHAVE (1962) to depend not only on the particular organisms present in the different environments, but also on the size of the organisms, selective physical destruction, transportation, and differential solution. In addition to these, the work of MAXWELLet al. (1964) suggested that selective removal of various components by winnowing and differential transportation-accumulation is significant. CHAVE(1962) illustrated that in the recent reef complex in North America studied by him, the highest ratio of high-Mg to low-Mg calcite is in the reef vicinity due to coralline Algae Lithothamnion and Lithophyllum, and encrusting Foraminifera Homotrema. The lowest value of this ratio is found in sediments from deeper waters because of the abundance of planktonic Foraminifera, e.g., Globigerina. The highest percentage of aragonite is present in shallow waters due to the abundance of the aragonitic corals and molluscs and aragonitic alga Halimeda in lagoons. This seems to agree with the observations made previously by CHAVE (1954a, b) and STEHLIand HOWER (1961) that only in quiet deep water is calcite the predominant mineral phase. In other parts, aragonite and high-Mg calcite form the main components of recent sediments. Inorganic processes may also control the mineralogy as suggested by CHAVE’S observations (1962) that: ( I ) near-reef sediments contain less aragonite than the nearby lagoonal sediments; and (2) the mineralogy changes with grain size. He concluded that inasmuch as the living reef is mainly composed of aragonitic madreporarian corals and molluscs, and that the calcitic alcyonarian corals, coralline Algae and Foraminifera are of minor quantitative importance (sometimes, however, they are responsible for the local high-Mg calcite concentration), it seems probable that a non-biologic process or processes remove aragonitic debris. Chave suggested that perhaps differences in durability of aragonitic versus calcitic material may be the causal factor. Change of mineralogy with grain size

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is reflected in a regular increase in mineral stability, with associated decrease in mineral solubility, from coarse to the fine fractions of the carbonate sediments (CHAVE,1962). According to him, there is a decrease in aragonite percentage and a decrease in the ratio of high-Mg to low-Mg calcite from the coarse to the fine sizes. This regular change has been found in a wide range of environments. For this reason, and because of the fact that the sediments of deep-water environments are largely composed of calcite, it appears that in the case of CHAVE'S(1962) studylocality, differential removal by washing and transportation to a more favorable site of accumulation is not applicable. Under other conditions such as those described by MAXWELL et al. (1964),however, a differential washing process may be of major importance. To understand his observations, Chave considered, among other explanations, inversion from aragonite to calcite and removal by solution as possible processes. Inversion was dismissed as an unlikely mechanism based on his belief that it would not be controlled by grain size in contrast to solution. Chave concluded, therefore, that solution is the most plausible cause of the regular increase in mineral stability with decrease in size. It should be noted, however, that in general the relationship between grain size and degree of inversion needs verification for reasons pointed out elsewhere in this chapter. A number of other independent investigations of Recent carbonate sediments indicated that selective removal by solution seems to be a rare phenomenon in the warm, shallow-marine environment. Age determination BARNES et al. (1956) suggested that it may be possible to date corals by the U-10 (uranium-ionium) method as far back as 300,000 years, because the 238U decay series in recently formed marine coral is systematically out of radioactive equilibrium. Subsequent investigations by TATSUMOTO and GOLDBERG (1 959) revealed the presence of substantial amounts of uranium in oolites, and studies thereof led to the conclusion that dating of oolites based on growth of ionium (thorium-230) from uranium also seems possible. BROECKER (1 963) furnished data, however, which demonstrate that fossil molluscs have a higher uranium content than living forms. Various lines of reasoning led Broecker to dismiss both the species effect and the change in U/Ca ratio of sea water during geologic time. He concluded that the excess uranium is secondary and of very early origin. One possible explanation for the excess of uranium being added shortly after death, while the organism was still in contact with the marine environment, is perhaps bacterial destruction of the organic matrix which sets up a microenvironment favorable for U precipitation. I t is important to note here that the origin of the uranium in organisms must be precisely known before the reliability of these materials for dating can be evaluated. (1963) also found that zz6Ra in any fossil carbonate can be divided BROECKER into five types according to origin and that only two are useful for age estimates. Thus, use of the Z26Ra/238Uratio in determining the absolute age of marine carbon-

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ates results in highly misleading ages. Broecker concluded that “criteria based on internal agreement of the isotopic data (i.e., 234U, 230Th, 226Ra, and where possible, 231Pa), other diagnostic parameters (microscopic examination, aragonite content, 13C/12C, 180/160, 232Th content, 238U content, 234U/238U, etc.) and material type (for example, coral and oolite are obviously more suitable than the average mollusk) will have to be developed”. Correlation based on composition K u D Y M o v ( ~in~ his ~ ~ book ) Spectral Well Logging has shown that correlation based on the minor and trace-element contents of carbonates and non-carbonate sediments can be most useful. CHILINGAR and BISSELL (1957) used Ca/Mg ratio for correlation purposes in studying the Mississippian Joana Limestone of the Cordilleran miogeosyncline. (Some discussion on this subject is presented in the section on “Regional aspects of carbonate composition” in this chapter. Basis for exploration philosophies GARLICK(1964) and MALAN(1964) described the pattern of metallic mineral distribution in reef complexes. Malan showed that copper is mainly concentrated in the inter-reef argillites. Various other attempts have been made, mainly by commercial companies, to use trace elements or other geochemical gradients to assist in the search for oil and gas deposits or metallic ore bodies. They have not been conspicuously successful to date; or if they have, the results have been kept as well-guarded secrets. Despite the difficulties that are bound to be encountered, the search for such indicators should be continued unless and until it has been proven futile. The objective is to develop criteria that are sufficiently diagnostic to reduce the number of test bore holes necessary for reconstruction of paleoenvironments and yet to permit conventional stratigraphic correlation. The present state of the research seems to be one of adding interesting corroboration of results already understood rather than one of developing an exploration tool. The authors were informed (confidential data), however, that the use of Ca/Mg ratios (plotting lines of equal Ca/Mg ratio and recording directions in which these ratios decrease) in locating dolomitized (and porous) carbonate oil reservoirs proved to be of value in some areas. INORGANIC FACTORS AND PROCESSES RELATED TO ELEMENTAL COMPOSITION OF CARBONATES

The problems related to the mineralogic and elemental composition of inorganically formed carbonates can conveniently be discussed under the following headings: ( 1 )inorganic physicochemical precipitation of calcium carbonates; (2) mechanical, volcanic, and cosmogenous contaminations; (3)magnesium in inorganic carbonates;

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( 4 ) strontium in inorganic carbonates; (5) other elements in inorganic carbonates, and associated contaminants; (6) elemental composition of environment controlling precipitation and stability of vaterite, aragonite, calcite, and dolomite; (7) environmental influence on the particle form of carbonate precipitates; and (8) influence of chemical composition of depositional medium on organisms.

Inorganic physicochemical precipitation o j calcium carbonates

The numerous parameters and processes that cause inorganic enrichment, depletion, and migration of chemical components cannot be considered in this chapter. Due attention has been given to them in other chapters of this book, and additional information is available in the publications by RANKAMA and SAHAMA (l95O), KRAUSKOPF (1955), GARRELS (1960), GOTO(1961), and others. Most interesting from the petrologic point of view is the recent observation made by ANGINOet al. (1964) indicating that inorganic processes, which are usually associated with warm and temperate climatic zones, can be expected to be operative also in unusual localities. Angino and co-workers observed the precipitation of gypsum (CaS04), aragonite (CaC03) and mirabilite (NazS04) in the permanently ice-covered Antarctic Lake Bonney where water temperature ranges from -3.5 O to 7 “C. These investigators stated that “an analysis of ionic ratios suggests that the lake waters may consist of trapped sea water highly modified by subsequent concentration by evaporitic processes, by addition of ions from surrounding soils, and by addition of warm spring water”. Mechanical, volcanic and cosmogenous contaminations

Any type of discrete detrital particle that can occur in sedimentary rocks can, in general, also be expected to be present in carbonates. Many of these mechanically added components constitute the “insolubles”, such as clay and different types of silt and sand grains. Under certain conditions, however, carbonate sediments can be diluted by calcareous and dolomite detritus derived from an older source. In precise geochemical studies these contaminations must be carefully considered, for the older carbonate-rock fragments may have been in equilibrium with a different physicochemical environment. Volcanic emanations, both on the continent and in the ocean, can contribute solid particles, as well as gases and fluids to an environment of carbonate sedimentation. Some of the geochemical problems involved were discussed by STRAKHOV (1964) who stated that little is known about the contribution of volcanic material to sediments in general, or about the chemical contamination arising therefrom. Cosmogenous contamination of shallow-water carbonates may be negligible because of the high rate of sedimentation and the possible immediate removal by

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reworking processes. In localities where the rate of accumulation is extremely slow, however, a cosmogenous source for some of the chemical constituents should be considered. WISEMAN (1964), for example, mentioned that the components of Mid-Atlantic deep-sea sediments are derived from lithogenous, biogenous, hydrogenous (= derived from the surrounding body of water) and cosmogenous sources. In this case, however, after taking into account numerous variables, Wiseman tentatively concluded that the presence of trace elements can be explained without assuming an appreciable addition from a cosmogenous source. Magnesium in inorganic carbonates

It has been mentioned earlier that the maximum MgC03 content of inorganically precipitated calcium carbonate is approximately 4 % in contrast to the maximum value of about 30% in organically formed carbonates. The statement of CHAVE (1954a, b) that there is no evidence of inorganic processes forming high-Mg calcite under surficial conditions appears to be in general true, but one has to count on minor exceptions and, in particular, on early diagenetic alteration of precipitated carbonates. In the study of naturally formed sediments, it is very difficult to determine whether the Mg in carbonates was coprecipitated (as MgC03, Mg ( O H ) 2 , x Mg CO3. y Mg ( O H ) 2 . z HzO, etc.) or whether it has been added diagenetically by adsorption-diffusion-absorption processes, for example. In doubtful cases, therefore, it is not possible to discuss the limits of Mg uptake meaningfully (or that of any other element) without first precisely knowing the mechanisms involved. The Mg in carbonates can occur as: ( I ) magnesite or hydromagnesite (e.g., ALDERMAN and VON DER BORCH,1961); (2) dolomite (e.g., ALDERMAN and VON DER BORCH,1961, 1963; PETERSON et al., 1963; SKINNER 1963; TAFTand HARBAUGH, 1964); (3) ankerite (e.g., USDOWSKI, 1963a; BROVKOV,1964); ( 4 ) high-Mg calcite (e.g., KUBLER, 1962, mentioned calcite with 40 % MgC03; FUCHTBAUER and GOLDSCHMIDT, 1964, reported on a calcite with 18% MgC03; occurrences were also noted by STEHLIand HOWER,1961; SEIBOLD,1962; TAFTand HARBAUGH, 1964); and (5) low-Mg calcite (e.g., SEIBOLD, 1962; USDOWSKI, 1962; TAFT and HARBAUGH, 1964). SKINNER (1963) showed that the Mg of a sedimentary deposit can be present in more than one phase; the predominantly inorganic carbonates of South Australia investigated by her are composed of magnesian calcite, calcian dolomite and dolomite, and magnesite and hydromagnesite. Strontium in inorganic carbonates

The problems of Sr concentration in inorganically formed carbonates must be considered from two view-points: ( I ) contemporaneous coprecipitation of Sr, and (2) subsequent introduction of Sr into the carbonate. ODUM(1957b) stated that in most cases it appears that the Sr/Ca ratio of a carbonate is smaller than that of the

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solution from which the carbonate was precipitated. In some occurrences, however, some very high Sr/Ca ratios were observed indicating that certain sedimentary processes can lead to Sr/Ca values equal to or greater than those of the aquatic medium. In one case the ratios were comparable: the Sr/Ca ratio of the oolite sediments, Great Salt Lake, Utah, is 4.23/1,000 atoms and is nearly equal to that of the water (4.20/1,000 atoms). Odum mentioned that if the solubility products are much exceeded, and if the solutions have no possibility to exchange with a large reservoir, precipitation occurs in a closed system and the Sr/Ca ratios of the precipitates are equal to those of the solution. For example, in five experiments the addition of sodium carbonate to sea water (Sr/Ca = 9.0/1,000 atoms) at various rates, produced in all cases calcium carbonate precipitates with Sr/Ca ratios ranging from 4.9 to 13.3/1,000 atoms. Similar results were described by ZELLERand WRAY (1 956). They also found that the Sr/Ca ratio increases with successive precipitation. WATTENBERG and TIMMERMANN (1938, in: SVERDRUP et al., 1952, p.211) reported that the solubility product of carbonate in sea water is approximately the same for both Sr and Ca (5 * lo-’), in contrast to distilled water where it is much smaller for strontium carbonate (0.3 * than for calcium carbonate (5 10-9). This suggests that the Sr/Ca ratios of directly precipitated carbonate should be higher in lowsalinity water. On investigating the coprecipitation of Sr with calcium carbonate from aqueous sdutions, OXBURGH et al. (1959) found, in agreement with many other investigators, that Sr2+ ions are much more readily precipitated with aragonite than with calcite. They also mentioned that it is possible to estimate the Sr2+/Ca2+ ratio of the solution from which the precipitation took place. GOLDBERG (1957) stated that examination of inorganically precipitated calcium carbonate from sea water in the laboratory, and studies of artificially prepared oolites, show that aragonitic structures contain more Sr relative to Ca than does the sea water. On the other hand, the Sr/Ca ratio in sea water is higher than that of most aragonite-precipitating organisms. HOLLAND et al. (1963) discussed the chemical composition of ocean water and its bearing on the coprecipitation of Sr with oolites. They stated that according to the mean value of the concentration of Sr as compared to Ca, one should expect a content of about 9,060 p.p.m. of Sr in aragonite precipitated from sea water at 25°C. Holland and co-workers mentioned that this is within the range of values found for the Sr concentrations in oolites from Cat Cay, Bahamas. ODUM(1957b) made it clear that it is difficult to evaluate the applicability of the principle that rapid or restricted inorganic precipitation gives rise to high Sr/Ca ratios, because the exact physico chemical mechanisms are still in dispute. For example, aragonite-needle deposits are believed by some to be derived from calcareous Algae, whereas others have suggested a bacterial or physico chemical origin. Future investigations of the Sr/Ca ratios may cast some light on these problems. As Odum indicated, the situation is made somewhat difficult by the

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presence of reef corals and aragonitic green Algae having Sr/Ca ratios of 9-12/ 1,000 atoms and 10-13/1,000 atoms or greater, respectively. The Sr/Ca values are high (9/1,000 atoms or greater) in three occurrences (in the Bahamas, Key West, and fossiliferous carbonates of Miami), where direct precipitation is assumed by some investigators: ( I ) unconsolidated and consolidated oolite (9/1,000 atoms); (2) drewite (9.3/1,000 atoms); and (3) consolidated and cemented rocks composed of fragments of taxonomic components originally not high in Sr content. The high Sr/Ca ratio of the drewite is comparable to the high value of calcareous green Algae; however, it is also similar to the Sr/Ca ratios of some types of inorganic precipitates from sea water. The Sr/Ca ratio does not, therefore, allow a precise evaluation of depositional environment. The mechanism that results in the cementation of beach-rock is still problematic, and the explanations vary from inorganic to organic processes, as reviewed by CHILINGAR et al. (1967). ODUM(1957b) mentioned Cloud’s suggestion that bluegreen Algae in the upper zones cause solution and reprecipitation due to large diurnal pH changes associated with algal metabolism. It is possible thatc)he high Sr/Ca ratios of all reef corals are due to the fact that the skeleton-building colonies contain symbiotic Zooxanthellae and green Algae which produce similar pH changes. Hence, the Sr/Ca ratios of cemented beach sands, calcareous Algae, and reef corals may all be related to the algal processes. It must be concluded, therefore, that studies of minor and trace elements of the beach-rock cement may be helpful in understanding its precipitation. Textural features of Devonian and Recent reef limestones support the concept that Algae can cement beach sands (WOLF, 1963b, 1965~).ODUM(1957b) suggested that if rapid precipitation is required for oolite genesis, the very great vital activity of organisms (photosynthesis) in shallow water and reef environments may be partly responsible. High Sr/Ca ratios (greater than 9/1,000 atoms) may be a paleoecological indication of algal photosynthesis. More research, however, is needed before this line of reasoning is substantiated. In the above discussions it was assumed that the Sr was located in the carbonate lattice. Under favorable conditions, however, celestite may form as an accessory mineral in carbonate sediments. SKINNER (1963) pointed out that in the recently formed sediments composed mainly of calcite and dolomite, the Sr is present as celestite, and the Sr content ranges from 0.28 to 1.12%. The strontianite deposits discussed by HARDER (1964) have been explained by some as being the product of lateral-secretion processes of solutions which derived the Sr from the limestones and organic skeletons. Others have suggested a hydrothermal origin. Harder showed that the limestones and fossils do not indicate any depletion of Sr and that there are no lateral changes in Sr content from the limestones to the strontianite layers; this precludes a lateral-secretion origin. Inasmuch as hydrothermally generated strontianite usually contains Ba, Cu, Pb, Zn, and other elements, and because Harder found that these elements are either absent or are present in traces, he concluded that a hydrothermal origin is

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also unlikely. He proposed, therefore, that ascending solutions from the lower Zechsteinsalzen rocks (evaporite-rich deposits) precipitated the strontianite. The fact that the calcite was deposited prior to strontianite indicates that NaCl solutions carried the Sr, because fresh water would have precipitated strontianite first. This supports the viewpoint that the Sr was derived from the lower evaporites. Other elements in inorganic carbonates, and associated contaminants A number of trace elements, other than Sr and Mg, have been reported from inorganically formed carbonate fractions of limestones. Considering the bulk composition of carbonates, it is frequently very difficult to make a distinction between the carbonate portion and the non-carbonate “impurities”. For example, DEGENS et al. (1962) determined the concentration of the following trace elements (in p.p.m.) in petroleum-bearing fresh-water carbonate concretions: B(290-420), Mn(35400), Ni( <2-8.9), Ti(65-1,040), Cu(4.8-25.0), Zr( < 10-92), Cr(3.7-9.2), V( 11-38), Ba(90-850), and Sr( 110-> 3,000). It is not quite clear to what extent some of the elements in the concretions may have been adsorbed-absorbed from the petroleum. OSTROM (1957) stated that “the average content of barium, manganese, and strontium, and the average range of Ba and Mn in the limestone samples, are higher than the averages and ranges of these elements in the shale samples. This suggests that these elements commonly are more closely associated with the minerals composing limestone than those of the shales”. The average amounts and ranges of the other twelve trace elements studied by Ostrom (ByCr, Cu, FeyPb, Mo, Ni, K, Na, Ti, V, Zn) are highest in the shales. The data on Ba given by Ostrom differ from those furnished by LANDERGREN and MANHEIM (1963). As shown in Table XI, there is no enrichment in the case TABLE XI DISTRIBUTTONOF

Ba AND Sr IN

SEDIMENTSOF THE PACIFIC (glton)

and MANHEIM, 1963, table 6) (After LANDERGREN

Ba content (average) Ba content (range) Ba/Ca ratio Ca content (average) Sr content (average) Sr content (range) Sr/Ca ratio

Clay sediments

Calcareous sediments

1,170 300-2,500 0.12 9,600 200 85-580 0.021

1,070 800-1,350 0.0035 306,000 1,480 940-2,000 0.0048

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ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

of Ba. On the other hand, Sr content is higher in calcareous sediments than in clay deposits by a factor of 7; this, in general, agrees with the observations of Ostrom. In this connection, it is interesting to note that in the algal bioherms studied by MALAN(1964) the copper is concentrated not in the carbonate deposits but in the inter-reef argillites. Malan concluded that this type of occurrence supports a syngenetic origin of the metalliferous deposits, because secondary processes would most likely concentrate the copper within the carbonates. The latter have greater susceptibility to solution, and replacement, than the argillites. This leads one to the controversies of syngenetic versus diagenetic and epigenetic origins of chemical components in carbonate skeletons, minerals, and rocks that are considered in some detail later in this chapter. K. G. BELL(1963) mentioned that the average content of syngenetically formed uranium of carbonates is <0.00014.021%, whereas that of uranium of epigenetic origin is 0.0005-1.19 %. The syngenetic uranium contents (in parts per million) of inorganic and organic carbonates are as follows (TATSUMOTO and GOLDBERG, 1959): (1) oolites0.83-5.8; (2) calcareous skeletons-up to 3.2; (3) aragonite (precipitated in the laboratory from sea water)-2.64.6; and ( 4 ) manganese nodules-3.6-5.0. The thorium content of oolites is up to 2.0 p.p.m. (1957) stated that uranium contents of oolites compare favorably GOLDBERG with those of chemical precipitates in the laboratory, but differ distinctly from those of organic material. In regard to the doubly charged ions cadmium, tin, and manganese, GOLDBERG (1957) pointed out that they may show a similar substitution pattern to that of Sr. They may be useful in characterizing environments inasmuch as contents of these ions differ markedly in, for example, fresh and marine waters. Investigations on chemical genesis and diagenesis, for instance, require precise chemical analyses of particular components of the sediments rather than of the bulk sample. This has been illustrated by USDOWSKI (1962) who presented the chemical data on the ooids and matrix of a carbonate rock (Table XII). TABLE XI1 COMPARISON OF CHEMICAL COMPOSITION OF MATRIX AND OOIDS

(After USDOWSKI, 1962)

Matrix

1.43-2.02

0.39-2.20

1,726-3,675

Ooids

0.46-0.79

0.16-0.18

744-1,314

380-676 189-381

110-120 (2,600) 276-383 (3,210)

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Future studies may lead to the application of non-carbonate minerals present in carbonate sediments for paleoenvironmental interpretations. RUCKERand VALENTINE (1961), for example, suggested that the Na content of some shells, in spite of being trapped in interstitial salts rather than forming part of the carbonate crystal lattice, may be useful in determining paleosalinity. Elemental composition of environment controlling precipitation and stability of vaterite, aragonite, calcite, and dolomite

A large proportion of the Pleistocene and Recent calcareous sediments are composed of aragonite and high-Mg and low-Mg calcite, of which the former two are considered to be unstable. It is believed by many scientists that they either convert to low-Mg calcite or are replaced by dolomite. Although general theories have been available for some time, precise information has been lacking on (I) the numerous factors that cause the genesis of all these minerals, and (2) the relative stability of the carbonate minerals once formed. The following is a brief review of some of the relevant literature. In his experiments on the deposition of calcium carbonate in caves, MURRAY (1954) found that: (I) Those waters from which aragonite precipitates tend to have a higher Mg/Ca ratio than do those depositing calcite. (2) The addition of Mg(HC03)z to a solution of Ca(HCO&, or the replacement of Ca by Mg ions, increases the proportion of aragonite in the calcium carbonate precipitated. When concentration of Mg is approximately equal to that of Ca, aragonite seems to predominate over calcite. (3)Aragonite appears to be less abundant among the first crystals that appear than among those precipitating later. (4) The presence of Sr and Pb is effective in much lower concentrations than is required of Mg in causing aragonite precipitation. (5) Ba, Mn, and SO4 ions considerably in excess of the other ions used were ineffective in causing the precipitation of aragonite in the test-tube experiments performed. (The fact that Ba did not cause the formation of aragonite contradicts the work of others, as discussed below.) (6) A slight increase in temperature increases the proportion of aragonite. The results of ZELLER and WRAY(1956) indicated that the form of calcium carbonate precipitation is strongly controlled by the content of impurities in the crystals. This impurity content, in turn, is greatly affected by impurity ion concentration and the type of ions in the original solution, the pH, temperature, the solubility of the polymorphs, crystal size, and the time of exposure of the crystals to the solutions. The above authors pointed out that a close interrelationship exists between these factors, and showed that high p H and temperature, low Mn2f and high Sr2+, Ba2+, and Pb2f concentrations favor the precipitation of aragonite

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from a solution of Ca(N03)~on the addition of N a ~ C 0 3 .Calcite formation is favored by lower p H and temperature, and by high concentration of Mn2+ and low concentrations of Sr2+, Ba2+, and Pb2+. The observations made by WRAYand DANIELS (1957) showed that: ( I ) It is relatively easy by controlling temperature, pH and duration of experiments to get either calcite or aragonite, or both. (2) The temperature range is small and very critical. (3) Aragonite may change rather rapidly to more stable calcite when in contact with certain solutions and that this rate of change is indefinitely slow in the dry state. ( 4 ) The aragonite lattice structure favors inclusion of cations (e.g., Sr, Ba, Pb,) larger than the Ca ion. (5) The formation of aragonite is induced by the presence of Sr, Ba, and Pb under high p H and other conditions that favor their co-precipitation with calcium carbonate; consequently, these ions are incorporated into the lattice of the aragonite. (6) At low pH, the Sr, Ba and Pb carbonates do not precipitate and the initial colloidal calcium carbonate particles do not contain these larger ions; this favors calcite deposition. (7) Under favorable conditions, Sr having small concentration in solution is brought into the small volume of the first colloidal grains; this gives rise to a high concentration of Sr in these particles. (8)The colloid aggregates undergo subsequent orientation leading to crystallization. (9) Decrease in time available for the Sr, Ba, and Pb ions to diffuse out of the colloidal particles back into the solution, and those factors that shorten this time of escape, tend to produce aragonite. Conversely, factors that tend to lengthen this time before crystallization, enhance the genesis of calcite. (10) Higher temperatures accelerate the rate of crystallization and the ions have little chance to escape; this promotes the formation of aragonite. ( 1 1 ) The greater the concentration of precipitating ions, the greater is the tendency for the formation of colloidal deposition and thus the longer is the time available before crystallization occurs. Hence, greater concentration of ions leads to calcite if all other conditions remain constant. (12) Aragonite in contact with water goes into solution and the carbonate is reprecipitated as calcite because of loss of Sr to the Sr-deficient water. (13) After minimum concentrations of Sr and other critical impurities are obtained, further additions have little or no effect. GOTO(1961) conducted extensive experiments that led him to conclude that: ( I ) The most important effect on the preferential or selective genesis of aragonite and calcite is the solvation of water molecules. These molecules act upon the surface ions of the particles and cause a marked loosening of the atomic binding throughout the particles. Inasmuch as the denser structure of aragonite is less stable

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K. H. WOLF. G. V. CHILINGAR AND F. W. BEALES

than that of the open structure of calcite under the influence of solvation by the water molecules, the genesis of aragonite is favored in solutions with a diminished solvation effect of water. This can be brought about by mixing the water with some polar liquids having low dielectric constants, such as alcohols. Goto pointed out that the secretion fluids of most organisms are believed to be composed of such polar liquids, and the aragonite formation by organisms may be thus explained. (See also discussions and references in the earlier section on organic aragonite versus calcite genesis.) Future research on solvation effect of fluids of different organisms and natural environments, such as lakes, lagoons, and so on, may be valuable. (2) Inasmuch as the solvation effect of water is considerably hindered by thermal agitation of the water molecules, the formation of aragonite is favored by higher temperatures from 60°C to the boiling point in contrast to lower temperatures. (3) Because of the low entropy structure of aragonite, it seems that oqtheoretical grounds a high velocity of reaction does not favor the precipitation of aragonite. GOTO(1961) stated that although the slow reaction is of primary importance in the formation of aragonite, it is by no means enough, as a slow reaction also favors the genesis of the high entropical structure of calcite to the same extent. From the viewpoint of reaction velocity alone, however, it is always more difficult to form aragonite than calcite, and the difficulty of formation of aragonite increases with increasing velocity of the reaction. This leads to the considerations more directly related to the elemental composition of the solutions. ( 4 ) Both a comparatively larger pH value of the solution and a balanced proportion of Ca2+ and C032- contents may be favorable for the precipitation of aragonite according to GOTO(1961). In contrast, high concentrations of H+ ions appear to favor the formation of the more open structures of calcite and vaterite. Goto stated that the unbalance of Ca2+ and C032- contents seems to cause the absorption of foreign ions in the growing nuclei of each CaC03 variety, and this is usually unfavorable for the genesis of aragonite. (5) The experimental results of Goto indicate that Mg2+, Sr2+, and Ba2+ ions do not enhance the formation of aragonite. Mg2+ favors the genesis of calcite, whereas Ba2+ causes the formation of vaterite (p-CaC03). Goto stated “it may be confidently said regarding these facts that the diadochic substitution of Ca by Mg makes calcite more stable relative to aragonite and p-form, and the substitution by Ba makes the p-form more stable than the other two. It is a very interesting fact that, in the present experiments, no aragonite was found even in the presence of Sr2+, while calcite, in which an appreciable amount of Ca is replaced by Sr, could form under the same conditions. These facts prove the chemically nonnegotiable nature of aragonite, and this nature may be attributed to the low entropy structure of aragonite.” (See chapter on techniques of analyzing and examining

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carbonates, WOLFet al., 1966, for possible misidentifications of vaterite, Ca-bearing strontianite and aragonite as suggested by GOTO,1961.) CLOUD(1962) pointed out that “WRAY and DANIELS directly (1957, p.2033), and ZELLER and WRAYobliquely (1956, pp.145-147, fig.2), relate the effect of the supposedly controlling ions to pH; but . . . the same relation of aragonite to higher and calcite to lower pH seems more consistently interpreted in terms of carbonateion concentrations and free energy of reaction”. Cloud was not able to demonstrate that the mere presence of Sr or Ba, even in high concentration, causes the formation of aragonite (see also INCERSON, 1962). KITANO(1956a, b) has also determined the effect of numerous inorganic ions on the proportions of aragonite precipitated. TAFT(1962) pointed out that because aragonite is thermodynamically less stable than calcite under pressure and temperature conditions prevailing at the earth’s surface, some other factors must be responsible to cause the stability of aragonite and high-Mg calcite present in carbonates as old as the Late Paleozoic. Taft found experimentally that “inorganically precipitated aragonite in contact with distilled water and with solutions of Ca and Sr ions changed slowly to calcite at rates dependent on cation concentration and the temperature. If more than 5 p.p.m. of magnesium were present, however, the recrystallization did not take place. High-Mg calcite and vaterite in contact with solutions containing 1,300 and 240 p.p.m. of Mg, respectively, did not recrystallize. In another series of experiments, calcite was placed in a solution containing 1,330 p.p.m. of Mg (equal to its concentration in sea water), and C02 was added to dissolve some of the calcite. When the C02 was allowed to escape, aragonite and high-Mg calcite precipitated even though some of the undissolved calcite was still present. Mg ion is evidently an important factor in causing the precipitation and persistence of aragonite and high-Mg calcite rather than calcite in marine environments.” As long as there is at least one Mg ion for each unit cell of aragonite in direct contact with the interstitial water, transformation of the aragonite to low-Mg calcite, according to Taft, will not occur. This “critical concentration ratio” is approximately 1.0 for aragonite but remains to be determined for high-Mg calcite. It is interesting to compare Taft’s conclusions with those of GOTO(1961) mentioned above. The recently completed investigations by TAFTand HARBAUCH (1964) also appear to substantiate that the presence of enough Mg ions in interstitial waters prevents the transformation of metastable carbonates to more stable forms. (See also TAFT, 1967.) SIMKISS(1964) prepared artificial sea water (without trace elements) and added various solutions to examine the influence of particular ions on the mineralogy of calcium carbonate precipitation. He stated that if C02 is removed from natural sea water, aragonite is precipitated. Simkiss’ experimental results can be summarized as follows: ( I ) solution with only NaCl and CaC12 formed pure

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K . H. WOLF, G. V. CHILINGAR A N D F. W. BEALES

calcite; (2) solution with CaC12, MgCb plus NaCl precipitated aragonite; (3) in the absence of Mg but in the presence of NaCI, KCI, N a ~ S 0 4plus CaC12, the precipitate was found to be composed of calcite plus vaterite, and in some cases traces of aragonite were recorded as well. The genesis of vaterite was an unexpected result. Simkiss stated that the Japanese investigator KITANO(1962a, b) found that vaterite formation was favored by high temperature and a large concentration of Ba ions. Simkiss concluded that the p H in his experiments did not seem to have had any marked effect on the genesis of vaterite. Perhaps an increase in the speed of precipitation may assist in the formation of vaterite. This, however, requires experimental confirmation as Simkiss pointed out. JOHNSTON et al. (1916) believed that the presence of SO& ions in sea water causes the precipitation of calcium carbonate in the form of aragonite. DUNBAR and RODGERS (1957) stated that meteoric waters, being normally very low in salts, tend to destroy aragonite; and that if connate fluids rich in S O P content are trapped with aragonite in sediments, the aragonite may be preserved for millions of years. MONAGHAN and LYTLE (1956), on the other hand, reported that the sulfate in a prepared solution of calcium chloride and sodium carbonate induces the deposition of calcite, whereas Mg2+ ions cause the formation of aragonite. SIEGEL (1965) could not come to a conclusion regarding the effect of strontium on the formation of aragonite versus calcite in limestone caves, for even the calcite investigated by him contained measurable quantities of Sr. Siegel, however, did note a preferred association of Sr with the aragonite. The Mg concentrations determined by Siegel are notably higher in aragonite-calcite mixtures than in calcite alone. The data did not permit evaluation of whether Mg promotes aragonite formation as suggested by MURRAY (1954) in his cave studies. (For additional information on the significance of Mg see the work by USDOWSKI, 1963a; also a summary of his findings is given in the next section.) Siegel concluded that temperature is of primary importance in carbonate formation (in caves), but further research is required to definitely substantiate this. In studying the effects of the chemistry of environmental fluids on the formation of various calcium carbonate polymorphs, it is most important to give consideration to the influence of organic matter both in vivo and post-mortem in addition to inorganic ions, as has been illustrated in the section on organic carbonates above. Contradictory results obtained so far may well be associated withthe influences of organic matter, superimposed on those brought about by inorganic factors. Aside from the numerous publications available on the parameters that determine the origin of vaterite, aragonite and calcite, not much has, been reported on similar relationships related to other carbonate minerals. SHEARMAN et al. (1 961) concluded from their study of ancient carbonate rocks that gypsiferous solutions could bring about dedolomitization. TEODOROVICH (1955, 1960) showed on theoretical grounds that as a result of increasing NaCl concentration

97

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

to a certain limit, the solubilities of calcite and dolomite approach each other; and this gives rise to dolomite formation. According to MEDLIN(1959), the presence of NaCl in solution also extends the range of temperature at which dolomite can be (1964) mentioned that NaC1-containing solutions precipitate precipitated. HARDER CaC03 first and then SrC03, whereas in pure water the converse would be the case. Environmental influence on the particle form of carbonate precipitates Varying the numerous parameters has been shown to cause the formation of different mineralogic precipitates within the carbonate system. Similarly, the genesis of gel-like carbonate, aragonite needles, spherulites and oolites, for example, appears to be a reflection of a range of physicochemical and biochemical factors. Although much more experimental work is required, the two examples presented here illustrate some of the results obtained so far. MONAGHAN and LYTLE(1 956) stated that a carbonate-ion concentration of more than 0.002 mol/l in solution causes precipitation of spherulites, and concentrations of less than 0.002 mol/l induce the formation of needle-like crystals. That is to say, when the solubility products are much exceeded, as in the case of rapid precipitation, the formation of calcium carbonate occurs in the form of spherulites.

1 0

-

.-

6

1

4

1

3

2 1

1 1

6

1

8

1

4

2 1

1 1 1 1 2 4 8

1 1 1 1 1 1 1 1 1 0 16 3 2 6 4 1 2 5 2 5 0 5 0 ~ 1

16.5%

0

1 0

64 1

3216 1 1

c

P-

8 1

4 2 1 1 1 1 1 1

R M Nd*P

1 2

MgICa weight

1

4

ratio

mi 1 8

1 16

1 1 32'64

of the

solution

1 1 1 1 0 1252505W#w)1

F i g 5 CaC03 precipitation from solutions having different salt content and varying Mg/Ca ratios. Every dot represents a precipitation experiment. Mg/Ca ratio of sea water = 2.11, G = amorphous gel as determined by X-rays; A =aragonite; K=calcite; V=vaterite; Sph I =ooid-like, optically negative spherulites with visible radial-fibrous structure (30-40 mp in diameter); Sph 2=optically negative spherulite, without visible fibrous structure (5-10 mp in diameter); P = prismatic crystals (approximately 15 mp in diameter); Nd 1 =granular precipitate, partly rhombohedra1 (approximately 10 mp in diameter); Nd 2 =finely granular precipitate (approximately 1 mp in diameter). Two identical sets of figures at the lower and upper parts of the diagram 1963b; represent Mg/Ca ratios; e.g., Mg/Ca ratio of 1/0, 64/1, 32/1, 16/1, etc. (After USDOWSKI. fig.1; by permission.)

98

K. H.

WOLF,

G. V. CHILINGAR AND F. W. BEALES

Slower precipitation, on the other hand, favors the genesis of needles. They also discovered that sulfate-reducing Bacteria can cause the precipitation of “ooliths”. Monaghan and Lytle found that rhombic crystals of calcite formed from solutions having Ca2+ alone, Ca2+ plus Na2+ ,Ca2+plus K+, and Ca2+ plus S O P . On the other hand, solutions with Ca2+ plus Mg2+ gave rise to amorphous gel, which transformed upon standing into spherulitic crystals of aragonite and calcium carbonate monohydrate (CaC03.HzO). The investigation by USDOWSKI (l963b) demonstrated that the origin of amorphous calcium carbonate, vaterite, calcite and aragonite minerals, and their form (as spherulites, radial-fibrous and concentric oolites, and prismatic and granular crystals) are dependent on the Mg/Ca ratio and the salinity, among other factors. As shown in Fig.5, the experiments indicated that vaterite, calcite, aragonite and finally amorphous calcium carbonate gel (in that order, with stages where two occur simultaneously) were precipitated with an increase of Mg/Ca ratio from solutions having a salt content of 16.5 %and 3.6 %. The vaterite formed as,a finely granular or crystalline precipitate, the calcite deposited in the form of spherulites without recognizable radial-fibrous structure, and the aragonite gave rise to optically negative spherulites with distinct radial-fibrous appearance. Calcium carbonate precipitation occurred in the form of calcite, aragonite and gel from the solution having salinity of 0.5 % and with an increase in Mg content; however, no spherulites formed. The calcite occurred as finely granular or crystalline particles among which some rhombohedra were present. The aragonite precipitated as crystals with prismatic and pyramidal faces. No vaterite formation took place in this case. Thus, the experiments performed by Usdowski suggest that the Mg/Ca ratio determines the CaC03 polymorph, and the salinity controls the habit or structural form of the carbonate precipitate. Ooids or spherulites are formed when the Mg/Ca ratio lies between 2/1 and 8/1. The lowest limit of salt content necessary for ooid-genesis lies somewhere between 3.6 % and 0.5 %. Influence of chemical composition of depositional medium on organisms

It has been said earlier that chemical elements in environmental medium influence organic life, and that on the other hand organisms control elements either directly or indirectly. Up to now no consideration has been given to the possibility that specific types of elements, or certain concentrations of elements can be harmful to organic existence, and may result in dwarfed faunas and floras and, possibly, massmortality. Little information is available on these aspects as related to the geochemistry of carbonate sediments and most of the data are based on inferences and hypotheses. TASCH(1957) pointed out that the presence of dwarfed fauna in black shales may possibly be due to the prolific growth of Algae. Catastrophic death of organisms that normally live in upper water horizons can result from recirculation of

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

99

poisonous waters from the bottom, and noxious red water caused by the presence of certain phytoplankton. Selective toxicity of waters as far as animals and plants are concerned will change the ecological equilibrium and hence the composition of any carbonate deposits formed. Similarly, such important ecological controls as the salinity, nutrient concentrations and so on, will influence the living community. Because of the selective concentration of certain ions exhibited by different life processes, the elemental composition of any carbonate formed will, in turn, be influenced by faunal and floral variation. It is interesting to note here that CHILINGAR and BISSELL (1963) on theoretical and experimental grounds showed that possibly the high Mg/Ca ratio of Precambrian sea waters prevented the formation of hard protective and skeletal structures of organisms, or largely hindered their formation. FAIRBRIDGE (1964) pointed out that though the alkalinity in the Precambrian has been high, a high pcoZ could have kept all carbonates in solution, except in partly isolated lagoon or intertidal environments. Almost aN Precambrian carbonates show traces of Colleniu type (intertidal) Algae. It appears feasible to assume that not all organisms respond equally to the same elements and to the same ranges of concentrations. Whereas some organisms prefer specific elements, others find them harmful. Certain concentrations of chemical elements may exclude one group of organisms, whereas other types of life may even prefer high concentration of the particular elements. It would be most helpful in environmental interpretations to continue experiments on the factors (involving elements) that stimulate and factors that hinder the growth of various organisms.

DIAGENESIS-EPIGENESIS RELATED TO CARBONATE COMPOSITION

The field of carbonate diagenesis-epigenesis encompasses a large number of factors and mechanisms that alter the content of major, minor and trace elements, and texture and structure of individual carbonate particles and whole rock units. Partly to avoid controversy and mainly because one is concerned here with all “secondary” changes irrespective of when they have occurred, the term “diagenesis” and “diagenesis-epigenesis” must be considered here in its widest sense in contrast to the very restricted application used by CHILINGAR et al. ( 1967). “Diagenesis-epigenesis” includes all secondary processes except metamorphism. In this respect, it must be emphasized that present-day weathering of. ancient sediments results in changes that can easily be attributed by mistake to diagenetic or epigenetic phenomena. No extensive discussion of the numerous secondary processes is given here, inasmuch as they are covered in the various sections of this and other chapters of this book, and by CHILINGAR et al. (1967) elsewhere. In general, one has to admit

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K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

that little is known about each of the mechanisms listed in the next paragraph; this particularly applies to grain diminution (WOLF,1965b), as practically no data on its influence on chemical changes is available. In many investigations one resorts to more than one process to explain the field and laboratory observations. For example, loss of trace elements is explained loosely by either “leaching or recrystallization”, a gain of elements by either “adsorption, diffusion, or uptake in solid solution”. None of these terms mean much, unless the causes and processes they represent are precisely understood and given a solid geochemical foundation. Much remains to be done in applying chemical and metallurgical principles and concepts to geological problems, and in determining to what extent they are applicable to natural occurrences of minerals and rocks. For example, similar features observable in both synthetic metals and ancient carbonate sediments may not necessarily be the product of the same or similar causes, as has been pointed out by FOLK(1964). In relation to a chemical alteration of carbonates, the numerous diagenetic processes include: ( 1 ) inversion: aragonite to calcite; (2) conversion: high-Mg calcite to low-Mg calcite; (3) pseudomorphic replacement: carbonate by carbonate; (4) grain growth; (5) grain diminution; (processes I through 5 are commonly grouped and referred to collectively as “recrystallization”); (6) genesis of noncarbonate components; (7) solution, leaching and bleaching; (8) adsorptiondiffusion-absorption; and (9) precipitation of carbonate: cement and nodules. Inversion: aragonite to calcite

Some of the factors that cause or prevent inversion have already been mentioned. It is also important to note here that FUCHTBAUER and GOLDSCHMIDT (1964) described skeletons in which inversion was prevented by the clayey and oily matrix in which they were embedded. One problem that requires the full attention of researchers is the enigma of expulsion versus uptake of elements in relation to “recrystallization”, i.e., are they a cause or an effect of secondary changes. For instance, SIEGEL (1960) concluded that Sr has to be leached out of the calcium carbonate before inversion can take place, whereas others maintain that recrystallization (see next section) leads to the expulsion of trace elements. It seems possible that, depending on the circumstances and the types of elements concerned, either one or the other, or both, explanations may be true. On the other hand, SPOTTS(1952) believed that during recrystallization there is a possibility of Mg uptake from the connate fluids. KRAUSKOPF (1 955) mentioned that during inversion of aragonite to calcite, the liberated Pb, Zn, Ni, and Co may combine with traces of S from organic matter to form small grains of galena, sphalerite, millerite and linnaeite. LOWENSTAM (1954a) found that Serpulidae tubes with an initial aragonite content ranging from 53 to 96 %, after 1 year of exposure had an aragonite content

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

101

between 45 and 78 %. Extreme care should be exercised, therefore, if old museum specimens are used for carrying out mineralogic and trace-element studies. It has been suggested that grinding of aragonite specimens may cause an inversion to calcite. KRINSLEY (1960), however, stated that no such alteration was observed in his work. Conversion, pseudomorphic replacement, grain growth and grain diminution

As has been mentioned earlier in the discussion on inorganic carbonates, TAFT (1964) found that a high concentration of Mg in (1962) and TAFTand HARBAUGH sea water or interstitial fluids prevents transformation of aragonite and high-Mg calcite to the more stable low-Mg and Mg-deficient calcites. On the other hand, STEHLI and HOWER(1961) mentioned that although it is known that high-Mg calcite is the least stable among the carbonates present in the Recent sediments investigated by them, the ultimate disposition of the Mg released is still far from clear. Do the certain ions in interstitial fluids reach a critical concentration, at which further transformation of unstable to stable carbonate cannot take place until the fluids are diluted? It has been shown that recrystallization rates are controlled by the concentration of particular cations, e.g., recrystallization in solutions containing Ca2+ and Sr2f ions, and in distilled water occurs a t different rates. Consequently, one of the principal factors controlling recrystallization is clearly the degree of saturation and rate of migration of the sea water and interstitial fluids. There seems little doubt that recrystallization causes migration of elements but the processes are complex. For example, USDOWSKI (1962) showed that contents of Mg, Fe, Mn, Sr, and C1 in an oolitic limestone are comparable to those of an average limestone. The distribution of these elements, however, is particularly significant. Mg, Fe, Mn, and Sr are concentrated in the calcitic matrix (intergranular debris plus sparry calcite cement), whereas ooliths are enriched in C1. Usdowski explained the higher contents of elements in the matrix by assuming that recrystallization of the ooliths expelled these elements. The CI is thought to be present in inclusions in the ooliths. Circulating solutions were able to remove CI selectively from the intergranular matrix due to its high porosity and permeability, whereas they were not able to reach the inclusions in the ooliths. It seems that recrystallization did not affect these CI-containing inclusions. Clearly, more research is needed before the behavior of different elements is clearly understood. ODUM (1957b) found a noticeable difference in the Sr content of recrystallized in contrast to unaltered fossil specimens. He plotted the percent deviation of the Sr/Ca ratio of the skeleton from the matrix as a function of the percent deviation of Sr/Ca ratio of the fossil from its modern counter-part (ODUM,1957b, fig.lO). The distribution pattern of the points suggests that fossils and the matrix tend to have similar Sr/Ca values when the Sr/Ca ratios are low. On the other hand, when the Sr/Ca ratios of fossils are as high as those of unrecrystallized recent skeletons,

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K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

the Sr/Ca values of the shells are usually greater than those of the matrix. Odum pointed out that echinoderms and corals appear to be much more readily altered than brachiopods and molluscs. He concluded that it is doubtful whether many fossil echinoderms exist that have not undergone transformation, however well preserved they appear on the outside. Odum cited an example of three very well preserved Pennsylvanian urchins that have a Sr/Ca ratio of 0.89/1,000 atoms in comparison to 3.06/1,000 atoms in three recent urchins. In contrast, Odum found no such discrepancy between Pennsylvanian and Recent mollusca. He suggested that a very low Sr/Ca value of the order of less than 1/1,OOO atoms in certain skeletons may be a useful indicator of alteration. As pointed out by CHILINGAR (1962b) in the case of Mg content, however, there is a possibility of change in the chemistry of the oceans with time. KULP et al. (1952) made similar investigations on skeletons and found a definite relationship between recrystallized and unaffected fossil specimens: the former always had lower Sr/Ca ratios. These investigators suggested that the release of Sr during recrystallization may have given rise to the celestite (SrS04) that has been encountered in the same sediments. USDOWSKI (1963a) also presented evidence that cone-in-cone structures may have been formed by recrystallization of a marl and that this process was accompanied by a loss of both Sr and Mg ions. It has been shown by BANNERand WOOD(1964), among others, that recrystallization of calcareous skeletons takes place differentially and in a predictable sequence. The loss of trace elements by these skeletons, therefore, should be equally predictable. In addition to the effects of recrystallization on inorganic elements, it has been suggested by ABELSON (1959a) that this process leads to the expulsion and loss of amino acids and other soluble organic compounds. These, previously isolated from interstitial fluids, become mobilized upon recrystallization.

Genesis of non-carbonate components (e.g., celestite) ODUM(1957b, partly quoting NOLL,1934) mentioned that percolating waters are enriched and carbonate sediments are depleted in Sr content. Celestite (SrS04) forms when the Sr-rich fluids come in contact with sulfate either in solution or as a mineral. Inasmuch as the solubility product of SrC03 in sea water (5.10-') is smaller than that of SrSO, (lO-5), strontianite will tend to replace celestite and celestite, in turn, will replace gypsum. That this has occurred is indicated by studies of crystal pseudomorphs. Odum also pointed out that a number of investigators suggested that the celestite associated with dolomite deposits contains the Sr that was released by inversion of aragonite and/or by the dolomitization of the limestone. On the other hand, the possibility must be considered that the aragonite precipitation and/or dolomite genesis took place in a saline environment and that the celestite was formed directly from the sea water.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

103

Solution. leaching and bleaching

Removal of elements from carbonate minerals and rocks may be conveniently divided into processes that (1)result in the removal of bulk material by uptake into solution, and (2) leach the elements selectively from the material under attack. Bleaching of the carbonates can be due to either removal of components and/or by alteration in situ. Conversion of high-Mg calcite and high-Sr aragonite to calcite and aragonite devoid (or having only a trace) of Mg and Sr, respectively, has been explained as the result of “leaching”, for example. In a number of cases contradictory information is given on whether an element can be removed from a crystal that is in contact with a fluid, or whether complete solution and recrystallization are required to remove it from the crystal lattice. ZELLERand WRAY(1956) stated that Sr cannot be selectively removed without complete solution or recrystallization of the carbonate. On the other hand, SIEGEL(1960) mentioned that Sr can be leached from the carbonate lattice prior to recrystallization. In the case of magnesium, under suitable conditions (pH, etc.) it would go into solution and, therefore, would be selectively extracted from the carbonate rock. CHILINGAR (1962b) also pointed out the existence of disagreement among investigators as to the possible loss of Mg from calcareous skeletons to the sea water during and shortly after sedimentation. He exposed skeletons to sea water, which was changed periodically, for 4 months and found no detectable change in the Ca/Mg ratio. CHAVE(1954a, b) mentioned that the removal of Mg by circulating waters can be observed in the Pleistocene formations of southern Florida. The extensively leached oolitic limestone studied by him now has only 0.37 % MgC03, although it contains 15% of echinoids, Foraminifera and Bryozoa that originally were probably rich in Mg content. Here again, however, solution and reprecipitation could be involved. PILKEY (1964) in his study of Recent carbonate sediments restricted his examination to the <62, <31, and < 4 p size fractions “on the assumption that any post-depositional changes would be most obvious in the finer size fractions”. He found that the < 4 p fraction is usually more unstable (aragonite plus high-Mg calcite) than the < 64 p fraction. Pilkey concluded that selective mineralogical alterations due to solution and recrystallization play a secondary role, if at all, during early diagenesis of material near the depositional surface. Some objections, however, can be raised against Pilkey’s reasoning for general application. It has been pointed out earlier in this chapter that ,the degrees of stagnancy and saturation of interstitial fluids significantly control the stability of the so-called unstable carbonate minerals (aragonite and high-Mg calcite). As the movement of interstitial fluids is very slow (or practically nil in some instances) in the finer grained sediments, Mg-rich waters may prevent transformation of the fine-grained unstable

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K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

minerals. In contrast, the coarser sediments without a fine matrix permit rapid renewal of interstitial fluids and have a better chance to come in contact with waters that do not enhance the stability of aragonite and Mg-rich calcite. Nevertheless, under favorable conditions selective alterations affecting the finer fractions are possible. Inasmuch as different size-grades of carbonate sediments may contain specific minor and trace elements, it follows that if selective removal of certain size fractions is possible by solution, a selective extraction of chemical elements is a consequential possibility. A dsorption-diffusion-absorption

Adsorption takes place when some foreign ion or molecule is fixed to the surface of a solid. As pointed out by FYFE(1964; see also RITCHIE, 1964), absorption involves the preliminary surface adsorption followed by diffusion into the interior of the solid. Molecules adsorbed on a surface are frequently deformed and chemical reactions occur on the surface. KRAUSKOPF (1955) stated that the adsorption of ions on the grains of a growing precipitate occurs as a result of coprecipitation, occlusion, ion exchange, and isomorphic substitution. He referred to the original literature and discussed some of the difficulties encountered in setting up general rules to predict the behavior of ions. TEICHERT (1930) discussed some of the problems of adsorption; and a number of papers contain descriptions of experiments performed on the adsorption of ions on carbonate minerals. In general, however, as GRAF (1960) pointed out after summarizing the literature, there is meager knowledge on the subject, and some of the results appear to be contradictory and inconclusive. BISSELL and CHILINGAR (1958), for example, discussed diagenetic dolomitization and migration of Ca and Mg ions by diffusion. GARRELS et al. (1949) and GARRELS and DREYER (1 952) reported experimental data on the subject. The investigations of TUREKIAN and ARMSTRONG (1961) showed that calcareous molluscan skeletons are slightly enriched in Ba relative to Ca, as compared to sea water. On the other hand, molluscs discriminate slightly against Sr and much more so against Mg. According to Turekian and Armstrong, these phenomena suggest that the “adsorption properties of ions on the surface of the growing shell front or during complexing in the blood of the organisms has a strong effect on the ultimate trace-element content of a molluscan test. If it were a matter of simple substitution in the lattice, then Goldschmidt’s commonly quoted rules would be operative and Ba should be excluded relative to both Ca and Sr because of its much larger ionic radius. However, if adsorption and complexing are important controls, one might expect a greater enrichment of Ba than Sr in a growing shell.” GOLDBERG (1954, 1957) referred to surface adsorption or “scavenging” of minor and trace elements. This process depends on the size and charge of the

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

105

adsorbed ion and the topographical character and charge of the adsorbing surface. For example, Mn-, Al-, and Fes+-hydroxides are very efficient in scavenging. GOLDBERG (1954) proposed that an electro-chemical process is responsible for giving either a negative or positive charge to the sea floor. When the latter is positive, negatively charged manganese micelles will be attracted; and when negative, positively charged iron will accumulate. The manganese hydroxide will scavenge nickel and copper; and the iron hydroxide supposedly will scavenge cobalt. Goldberg also suggested that “the concentration of minor elements by members of the marine biosphere is explained either by the direct uptake of the element or by the uptake of iron or manganese oxides with the accompanying scavenged element”. LOWENSTAM (1963) pointed out that certain calcareous shells contain minute proportions of phosphate, iron oxide and sulfate that appear to be of organic origin; and that trace elements may be expected to be adsorbed on these non-calcareous specks. GOLDSCHMIDT (1937) and MASON (1958), among others, pointed out that clay minerals, particularly montmorillonite, have a marked adsorptive capacity for ions (mainly positive) in solutions. The amounts of elements (e.g., c o h e r , lead, arsenic, mercury, selenium), which have been supplied from the primary rocks to the oceans during the past geological periods, would have been sufficient to have caused serious poisoning of the ocean unless some mechanism had removed these elements. Goldschmidt stated that a number of the poisonous elements such as selenium, arsenic, lead, antimony, and bismuth, have been removed by adsorption on iron hydroxides. It would be equally valid to assume that even if the poisonous elements had not been removed, the organisms most probably would have developed a tolerance during evolution. Precipitation of carbonate cement and nodules

Investigations of both elemental and isotopic compositions in conjunction with textural studies of carbonate-cement types may prove to be useful in determining the time of formation of the cement relative to the sediment-framework and the mode of cement genesis. Consequently, this may show what types of cement are useful as paleoenvironmental indicators (WOLF,1963a, b; 1965a). The influence of living and dead organic matter on the precipitation of carbonate cement must also be given its due consideration (WATABE and WILBUR,1960). Further studies may lead to information that will solve the contradictory theories on beach-rock genesis. For example, if cryptocrystalline cement described by CHILINGAR et al. (1966) and WOLF(1965~)is indeed of algal origin, the Sr,and Mg contents of the cement should (as long as diagenesis did not cause secondary changes) correlate favorably with contents of these elements in products resulting from algal metabolism. Distribution patterns of elements in carbonate concretions have been shown to furnish valuable data on the relative mobility of certain elements during diage-

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K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

nesis-epigenesis. For instance, LOGVINENKO and KOSMACHEV (1 961) examined carbonate (Mg, Ca, Fe, Mn) concretions and found that the Co, Sr, Ba, V, Ni, Cr, and Ti contents of the concretions and adjacent rocks indicate that the participation of different elements in the formation of the concretions varies distinctly. There is a direct correlation between the Co and Mn occurrences, for example, but in general the interdependency among the elements is more complex. Two groups of elements were recognized by these authors: (I) elements migrating in the stage of diagenetic redistribution of the material in the deposits (Co and Sr); and (2) elements that do not appear to undergo redistribution (Ba, V, Ni, Cr, Ti). A most interesting example of regional distribution of various types of carbonate cement and concretions described by BROVKOV (1964), is presented in the section on regional aspects related to carbonate chemistry. Chemical and physical changes brought about by diagenesis-epigenesis

In general, chemical and physical changes brought about by diagenesis-epigenesis can give irise to the following modifications and alterations: (I) Chemical changes or absence thereof: (a) no change; (6)change in mineralogy (e.g., aragonite to calcite); (c) removal of trace elements; ( d ) addition of trace elements; (e) change in content of isotopes; and (f)decomposition of organic matrix and matter, which in itself may lead to alterations of a chemical and/or physical nature. (2) Physical changes or absence thereof: (a)no change in texture and structure, and (b) change of texture and structure. In general, many of the earlier sections have included discussions on the numerous diagenetic-epigenetic alteration mechanisms, and only a few supplemental case histories that illustrate the above list of possible modifications are reviewed here. Some of the complexities to be expected in diagenetic changes are discussed by TUREKIAN and ARMSTRONG (1961) who set up a quantitative model to “encourage the viewing of a fossil shell of any age as a complex of alteration products”. In the case of the molluscs investigated by them, three “end-members” were considered: (I) original unaltered shell material composed of pure aragonite; (2) completely recrystallized material, either replacing the original shell or filling interstices; and (3) a “reaction layer” in which trace elements have been adsorbed on otherwise unaltered aragonite shell material. The reaction layer may be a consequence of the approximately 3 % of organic matter which is present as a network within the hard skeletons. Upon decomposition of the organic material, vacant interstices may be left and thus furnish a reactive environment for adsorption processes. Turekian and Armstrong pointed out that because alterations giving rise to phases 2 and 3 proceed at different rates in different environments, the ratios of these three phases are not simply predictable from

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

107

the calcite concentration. Assuming that each one of the phases has a distinctive trace-element composition, concentration of a particular element in a mollusc skeleton is equal to: Cim =

amxi

+

bmyi

+

CmZi

where C i m = measured concentration of element rn in shell chip i; xt = fraction of original aragonitic unaltered material in shell chip i ; y t = fraction of calcite in shell chip i; zi = fraction of “reaction layer” aragonitic in composition in shell chip i; xi yi zi = 1; and a,, b m , Cm = the concentrations of the trace element in the phases x i , y i , and zt, respectively. Analogous models can be set up for other skeletal types, i.e., for those originally composed of calcite only, or of both high-Mg and low-Mg calcite, and so forth. TUREKIAN and Armstrong (1961) found that similar molluscan fossil shells contain l-lO% calcite in contrast to the complete absence of calcite in similar modern types, which are composed of aragonite only. They assumed that secondary effects gave rise to calcite, and used the percentage of calcite of the sampled skeletons as an indication of the degree of diagenetic change. Turekian and Armstrong also found that the aragonite crystals of the fossil specimens are somewhat larger than those in the modern representatives; this could be due either to the species or diagenetic effect. The trace element versus calcite-content curves of Turekian and Armstrong indicate a general increase for Mg, Fe, Mn, and Ba with increasing calcite content. The curve for Sr is the most difficult to interpret. The highest Sr contents occur when calcite content lies between 2 and 10%; and these Sr concentrations are considerably higher than those of modern molluscan shells (average 1,600 p.p.m.). Upon reaching a maximum, the Sr content decreases with increasing calcite content toward the 100% calcite value. The Mg content shows a hundred-fold increase between the aragonitic and calcitic end members. The Mn content also exhibits a marked increase with increasing calcite content as indicated by a concentration of 500 p.p.m. of Mn for low-calcite shells. This is about 100 times higher than the Mn content of contemporary mollusc shells (KRINSLEY, 1959). The trend of the curve for Ba shows a slight increase in Ba content with increasing percentage of calcite. Three very high values recorded by TUREKIAN and ARMSTRONG (1961) may be due to the presence of barite. On the other hand, even where the shells are almost totally composed of aragonite, an average content of Ba is about 130 p.p.m., which is more than 10 times the average for modern molluscs. The Fe content also increases with increasing amount of calcite, but the spread of values is larger. In addition, aragonite specimens are much higher in Fe content than their contemporary equivalents. After considering the possibility that either (I) the shells having lowest calGite content are the closest approximation to the original shell, or (2) the composition reflects the multiple effects of diagenesis and weathering, Turekian and Armstrong subscribed to the second alternative. Because of the unusually high

+ +

108

K. H. WOLF, G. V. CHlLINGAR AND F. W. BEALES

Fe and Mn concentrations and the increase of Sr and Ba contents by factors of two and ten, respectively, an interpretation based on diagenetic changes is more plausible. Important for future research are two further conclusions reached by TUREKIAN and ARMSTRONG (1961): ( I ) that visual appearance of shell material is not necessarily a valid indicator of degree of alteration, and (2) that even where there is no apparent alteration in mineralogy, there may be an alteration of the original chemical composition of the shell. In addition, they doubt if the composition of molluscan external hard parts are useful for paleoecological reconstructions. The loss of Sr from the carbonate particles during fossilization and diagenesis has been reported by KULPet al. (1952), ODUM(1957b), and SIEGEL(1960), for example; whereas KRINSLEY (1959) found that Sr and Cu contents (with one exception) in his samples remained constant. Krinsley also reported that Al, Mn, and Mg contents are higher in pteropod shells from cores in contrast to the shells of plankton samples. Krinsley suggested that the higher concentrations are the result of uptake of these elements from the ocean bottom sediments. As Sr and Cu contents did not change, he suggested that they may be used as standards in the study of post-depositional changes. In view of the contradictory results obtained for Sr by different investigators, however, this may not be possible. TUREKIAN (1959) found a notable enrichment in Ba, whereas Sr content appears to undergo the least change. PILKEYand GOODELL (1964), comparing the composition of fossil and recent mollusc shells, determined that the aragonitic shells of older specimens usually have higher Ba, Sr, and Fe contents, and lower contents of Mn and Mg than their modern representatives. In one calcitic species, the average Sr and Mg concentrations were lower in the fossil, whereas the other elements did not show statistical differences between the Recent and fossil specimens. Of particular interest are the “inter-specific variation” and the “element-element correlation” illustrated by Pilkey and Goodell. Curves illustrating the former concept indicate that interspecific variations in composition of fossil and contemporary aragonitic skeletons are similar only for Mg and Sr, whereas Ba, Fe, Mn and calcite contents in the older skeletons illustrate inter-specific variations different from those of the Recent shells. In examining the element-element correlations, PILKEY and GOODELL (1964) found that in some cases Ba and Mn contents of fossil, but not of Recent, shells are directly related; whereas in other instances Fe and Mn contents show a strong correlation. Again these changes are explained as being due to diagenesis and possibly to weathering. Pilkey and Goodell concluded that the available evidence favors post-depositional alterations which have occurred mainly within the crystal lattice, and that the nature and properties of the bonds formed or broken are more important than the similarity of ionic radii to Ca. The changes are such that they increase the stability of the crystal lattice. Hence, the contents of elements that enhance the stability will increase and contents of those that decrease the stability

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

109

of the crystal lattice will diminish during secondary processes. Based on this concept, Pilkey and Goodell listed the elements in order of increasing “desirability” in the aragonite lattice under post-depositional conditions as Mn <Mg <Sr
K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

110 TABLE XI11 DIAGENETICCHANGES IN

lSO/lsO RATIO AND SrC03 AND MgC03 CONTENTS OF BRACHIOPODA

(After LOWENSTAM, 1961, p.255)

Initial stage of diagenetic alteration Intermediate stage of diagenetic alteration Most advanced diagenetic alteration

no change - 0.8

no change 15

45 50

- 1.2

20

50

water low in Sr, Mg, and 1 8 0 contents. It is interesting to note the progressive and selective diagenetic alterations as illustrated in Table XI11 (based on the data given by LOWENSTAM, 1961).The values are compared to those of unaltered brachiopod specimens. The study conducted by Lowenstam illustrated that of fourteen fossil specimens, 1 8 0 / 1 6 0 ratio was preserved in nine samples; SrC03 content, in eight samples; and MgC03 content, in two specimens. The results indicated that the oxygenisotope ratios are the most stable and the Mg content, the least stable. By comparing the 1 8 0 / 1 6 0 ratios and SrC03 concentrations in fossil and in Recent skeletons, it is possible to distinguish original from diagenetically depleted MgC03 contents. With an increase in diagenetic alteration and the formation of secondary calcite, the fossils usually have lower 180/160 ratios and are significantly depleted in MgC03 and SrC03 contents. Relationships between the Ca/Mg ratios, on one hand, and silicification and dolomitization (and porosity) on the other, have been described by CHILINGAR and TERRY(1954) and CHILINGAR (1956b, c). In the section on skeletal carbonates it has been mentioned that once the chemical composition of Recent shells has been determined to a reasonably reliable degree, they can be used as “standards” or “norms” for the study of fossil specimens. Similar extrapolations in the study of inorganic carbonates may be possible, but most likely will prove to be difficult. For example, SKINNER (1963) found that the recently precipitated carbonates in the Coorong lagoon, South Australia, range in composition from Ca0.77 Mgo.23(C03)2 to Cao.gsMgo.oz(C03)2. Investigating older carbonate sediments in the district of the Coorong, Skinner found evidence suggesting that they formed under similar conditions; however, these carbonates have compositions ranging from C ~ O . W ~ M ~ O . I Zto ( CCao.98O~)Z Mgo.oz(CO3)2. If they had the same original composition as the carbonates of the Coorong lagoon, then recrystallization and/or leaching possibly changed the composition.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

111

REGIONAL ASPECTS OF CARBONATE COMPOSITION

In the preceding sections no consideration has been given to possible regional or facies changes in the composition of carbonate sediments, and the chemistry was discussed in view of more local factors and processes. The significance of regional aspects goes far beyond mere academic considerations and is of interest to both metalliferous and non-metalliferous exploration geologists alike. Surveying the literature on regional chemical changes in carbonate rocks, one will find that the amount of available information is meager. This seems to be predominantly a reflection on the lack of methods that would permit a rapid, and yet reliable, analysis of many specimens. On the other hand, literature (in particular Russian publications) furnishes sufficient analytical data for case history studies of which some are considered below. As in many other branches of geology, it may be relatively easy to make reliable determinations of a number of parameters, in this case of chemical elements, but any interpretations based upon them are at present largely speculative and frequently contradictory. The problems of reconstructing past events on the basis of chemical composition have been pointed out by CLAYTON and DEGENS (1959) as follows: “DEGENS et al. (1957, 1958) have demonstrated that trace-element data for a complete rock sample are less conclusive and sometimes not interpretable with reference to their environmental grouping than analyses of certain mineral fractions. Analytical data on separated detrital or chemical end members, i.e., clays, carbonates, sulphides, organics, allow more conclusive interpretation of the environmental conditions during sedimentation than trace-element analyses on the total rock sample. In addition, correlation between two or more variables was found to be more useful for the environmental classification of sediments than the absolute values of one element.” According to CLAYTONand DEGENS(1959), “the great defect in traceelement investigations is the lack of a world-wide absolute environmental standard both marine and fresh water. This is mainly caused by the local variation in traceelement supply (i.e., source effects). Although certain elements are found to be generally useful as fresh-water or marine indicators, each geological or geographical area has to be evaluated separately by establishing new correlation standards.” Sr, Mg, and CalMg ratio distribution

Strontium variations in reef complexes have been studied by FLUGEL and FLUGELKAHLER(1962; Sauwand limestones) and .STERNBERG et al. (1959; Steinplatte limestones), among others. These investigators found a gradual increase of SrC03 content from the back-reef to the basin limestones (Fig.6). STERNBERG et al. (1959) reported values of 60-1 50 p.p.m., 150-420 p.p.m., and 3804,570 p.p.m. SrCO3 for the back-reef, fore-reef and basin sediments, respectively. Their investigations

112

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

1

reef

back-reef

, , \

?,

'

\

fore-reef

'. ?' ,

---?

basin

--____

Fig.6. A. Distribution of SrC03 in the Sauwand and Steinplatte Reef Complexes. (After FLUGEL and FLUGEL-KAHLER, 1962, fig.11; by permission.) B. Approximate (very diagrammatic as precise numerical values are not given) trend of the Sr content reconstructed from descriptions (1961) illustrating the decrease of Sr from the reef to the fore-reef facies in contrast to by SIEGEL the occurrence shown in Fig.6A.

indicated that carbonates which have undergone recrystallization have low Sr contents due to depletion. This interpretation is supported by the high Sr values of unrecrystallized reef samples. The relatively high Sr content and the well-preserved organisms in the basin sediments indicated that diagenetic to epigenetic depletion due to recrystallization has been less intense here. FLUGEL and FLUGEL-KAHLER(1962) concluded that recrystallization lowered the Sr content of the Sauwand limestones. They postulated that depletion of Sr took place in more or less equal proportions in both the back-reef and reef facies so that the present Sr,content still gives some idea as to the d a t i v e proportions of the original Sr contents. In general, however, one has to expect differential recrystallization according to the mineralogically different types of carbonates (e.g., aragonite, high-Mg calcite, low-Mg calcite) and different environments of formation (e.g., fresh water, lagoon, reef, basin). The final trace-element composition after diagenetic-epigenetic recrystallization, therefore, may be very complex and difficult to interpret. FLUGEL and FLUGEL-KAHLER(1962) reported that there are no systematic changes in the amounts of MgC03 with changes in the SrC03 content in the ancient rocks they studied. On the other hand, SIEGEL (1961) found that in Recent carbonate sediments the Mg concentration decreases as the Sr content increases and reaches a maximum where Sr content is at a minimum. The iso-strontium/calcium atom ratio lines plotted by Siege1 showed that Sr/Ca ratio of the sediments increases with distance offshore from the Pleistocene reef and as the living reef is approached. The highest value for Sr content is reached about 1 nautical mile on the leeward side of the living reef and decreases at the reef and seaward from it (Fig.6). As the reef organisms consist mainly of aragonite with a high Sr content, these results suggested that most of the reef-debris is deposited about 1 mile on the leeward side of the reef, thus causing the shift of the maximum of the curve.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

113

So many different factors control the distribution of both Mg and Sr within a reef-complex, that it is most difficult to, first, make generalizations, and, second, use findings on Recent carbonates in the interpretation of ancient reef-complexes. If carbonate differentiation as reported by MAXWELL et al. (1964), which is due to differential breakup of aragonitic and calcitic skeletons, is extensive, a number of other factors will determine whether the fine, Sr-rich detritus will be transported to lagoons or to the deep-sea basin. Hence, a Sr maximum may be found either on the leeward or seaward side of the reef. Many ancient reefs are composed mainly of calcareous Algae and it is most difficult to predict both Sr and Mg maxima in this case. CHILINGAR (1960) found that the Ca/Mg ratio of carbonate sediments increases on going away from shore, which can be attributed to the abundance of Mg-rich coralline Algae in the near-shore waters. The Devonian Nubrigyn Reef Complex of New South Wales (WOLF,1965a) has been shown to comprise many algal bioherms, some lagoonal deposits, and algal debris washed in the opposite direction to form the “turbidite” facies of the adjacent basin. Where all facies are composed of algal components, Sr- and Mg-differentiation of skeletal origin may be poor to absent, unless physicochemical processes independent of the mineralogy of the organisms caused secondary differentiation of the trace elements at the site of accumulation. ODUM(1957a) pointed out that knowledge of the geochemical cycle of Sr is most important for the understanding of the regional and local distribution of strontium. Variations in Sr/Ca ratios during sedimentary cycle are presented in Fig. 7. ODUM(1957b) stated that the Sr content is higher in sediments of isolated lakes than in those of open lakes, for cases in which the chemical natures of drainage are similar. Generally, sediments of closed basins have a high Ca content; however, open basins also can have a wide range of Ca values. Isolated or closed lakes should have Sr/Ca ratios comparable with the ratios of the inflowing tributary waters. In open water bodies the rate of Ca extraction due to precipitation may be less than the rate of Ca inflow. In addition, if Sr is excluded relative to Ca during SrlCa Rain

1

Attered Limestone

Surface Waters

uplift Intermediate 1.2- 2.5 Water

3.8

Unconsotidated

Fig.7. The variation of the Sr/Ca ratio during the sedimentary cycle. Values for various phases are means of data from the study of ODUM(1957a). Strontium is more readily removed into solution during consolidation than calcium. This behavior accounts in part for low values in limestones and high values in ground waters. (After ODUM,1957a, fig.5; by permission of the Institute of Marine Sciences, Texas University.)

114

K. H. WOLF, G. V. CHlLlNGAR AND F. W. BEALES

carbonate deposition in such lakes, the Sr/Ca values of the sediments will be less compared to those of the inflowing waters. In closed basins, then, the Sr remaining in the waters will build up to a higher concentration, whereas in open lakes an exchange with other water bodies is possible. It was found that the sediments of the Great Salt Lake (Utah), East Twin Lake (Connecticut), and Lake Mendola (Wisconsin) have lower Sr/Ca values than the lake waters. This substantiates the concept of Sr being excluded during deposition of calcareous sediments. Although the above explanation and data may be applicable in some cases, numerous other factors have to be taken into account that will cause deviations from any “norm”. TUREKIAN (1955) stated, for example, that his work points to the fact that there will not be very large increases in Sr/Ca ratio in evaporating arms of the sea. H. A. Lowenstam (personal communication to ODUM,1957b), however, gave data indicating that high Sr/Ca ratios exist in parts of the sea having high salinity. In general, according to Odum, the Sr/Ca ratios of marine carbonate sediments are higher than those of the calcareous deposits of open fresh-water basins. Because of the size and diversity of the ocean, however, a wide range in Sr/Ca values can be expected. Odum concluded that the Sr/Ca ratio varies partly with depth because of differential sedimentary accumulation of the calcareous deposits; this has been borne out by the work of others mentioned above. In some localities, the Sr/Ca ratio may be controlled largely by the variation in content of insoluble components. In areas where there is no chemical precipitation of carbonate sediment, the Sr/Ca ratio is determined by the taxonomic composition of the calcareous skeletons. In marine, as well as in lake sediments, as the Ca concentration diminishes, the Sr/Ca ratio approaches the value characteristic of the acid insolubles; and when the Ca content increases, the Sr/Ca ratio approaches that of the carbonates present. As mentioned previously, diagenesis-epigenesis can mobilize chemical elements. FOLK( I 962) postulated that brackish-water micrites recrystallize more readily than either normal marine or lacustrine fresh-water micrites. Geochemical profiles through a carbonate formation, that accumulated in a variety of environments, may offer the original or slightly altered composition in one area, whereas in other parts the chemistry has been markedly changed. This has been brought to attention in discussing the work of FLUGEL and FLUGEL-KAHLER (1962) and STERNBERG et al. (1959). KUBLER (1962) also found that both fresh-water and marine limestones contain the same amount of Sr and concluded that the Sr content may be independent of salinity. On the other hand, DEGENS’ (1959) studies showed that recent fresh-water limestones have a lower content of Sr than marine carbonate sediments; this is caused presumably by the lower amounts of Sr in fresh water. With an increase in age of limestones, however, the difference in Ca/Sr ratio between the fresh-water and marine sediments afipears to diminish; and the Sr contents of Paleozoic carbonates, independent of facies, do not deviate much from the average value of 500 p.p.m. Hence, fresh-water limestones must

1I5

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

have gained and marine limestones lost Sr (relatively speaking) during the geologic history as a result of diagenesis-epigenesis. A hopeful note was sounded by KUBLER(1962) who concluded that the Sr content is a useful parameter in environmental interpretations. In general, Kiibler found in his studies that the maximum content of Sr occurs in sediments containing aragonite; and that light-colored carbonates are poor in Sr in both Mg-calcite and dolomite in contrast to the darker carbonate rocks. During diagenesis the Sr appears to have been mobilized in some cases to form celestite. KULPet al. (1952) reported that Sr contents of the Mississippian sediments differ from those of the older limestones, and suggested that this may be due to difference in salinity. On the other hand, various samples collected 144 miles along the strike of one formation, the Harrodsburg Limestone (Indiana, U.S.A.), exhibited a constant Sr/Ca ratio which indicates homogeneous conditions of sedimentation. Only values collected from the southernmost part of the formation fall appreciably outside the range of experimental errors. In his studies of Recent carbonates, CLOUD(1962) found that the magnesium content of the calcite fraction is either high (1 1-19 mol%) or low (0.5 molx). The low-Mg calcite is particularly abundant in near-shore localities and in bottom core samples that reached bed rock. The abundance of high-Mg calcite increases offshore, and Cloud stated that it is probably all skeletal. Comparative investigations of carbonate provenance may show that each sedimentary region may have a characteristic range of mineralogic and/or chemical composition. Table XIV is based on the work of TAFTand HARBAUGH (1964) TABLE XIV RANGES OF MINERALOGIC ELEMENTAL COMPOSITION OF SOME MODERN CARBONATE SEDIMENTS

(Data after TAFTand HARBAUGH, 1964) Locality

Southern Florida Bahaman Islands2 Andros Island Baja California

Aragonite

CalMg ratio

SrlCa (x ratio

Mol % MgCO3 in high-Mg calcite

Low-Mg calcite

High-Mg calcite

( %)

( %)

0-89

1-100

0-54

6-1.51'

2-91

0-6

8-98

16.8-93.0'

5.0-16.0

45-99

0-1 3

1-51

22.1-212.3

13.5-16.0

38-90

I4 2

3-58

16.0-37.0'

( %)

1.7-15.1'

8.2-1 1.2

'The values were not determined for all samples. (See original publication for details.) Andros Island and Yellow Bank.

116

K. H . WOLF, G. V. CHILINGAR A N D F. W. BEALES

giving the ranges of aragonite, low-Mg calcite and high-Mg calcite contents, and Ca/Mg and Sr/Ca ratios. E. T. Degens reported on a detailed study of fossiliferous and unfossiliferous beds in Mesozoic and Tertiary limestones. E. T. Degens and his co-workers (personal communication to INGERSON,1962) concluded that (I) the Ca/Mg ratio decreases as salinity increases, and (2) fossils occur only in formations where the Ca/Mg ratio is greater than 50. The absence of fossils is believed to reflect hypersaline conditions. KUBLER (1962) described regional facies changes of two cycles of sedimentary units rich in carbonate sediments of lacustrine (fresh-water), brackish, and marine environments. In addition to numerous differences not considered here, each cycle exhibits a different carbonate phase. Calcite is the dominant mineral in the whole profile. In the fresh-water limestone of cycle one, the Mg present occurs as detrital dolomite. In cycle two, however, the Mg is present in the calcite lattice to form Mgcalcite of various compositional ranges. The interbedded carbonates associated with coal deposits contain the maximum amount of Mg-rich calcite having the highest Mg content. In any one hand-specimen, there are often two types of Mg-rich calcite: one with a MgCOs content of about 20 %, and an other with as high as 40% MgC03. The formation of Mg-rich carbonate sediments in Recent saline lagoons has (1 963) and ALDERMAN and VONDER BORCH(1 963), and been described by SKINNER in a number of other publications. Skinner reported on the saline Coorong lagoon which is an elongated finger of the ocean and is connected to the sea at the northern extremity. He also described a string of isolated, shallow, saline lakes which are isolated remnants of the Coorong lagoon. The amount of Mg being precipitated from the saline water in the form of carbonates appears to increase southward, away from the mouth of the Coorong lagoon, and reaches a maximum in the isolated lakes. The calcite/dolomite ratio seems to be distinctive for a particular lake or a particular position in the Coorong lagoon. As the amount of dolomite increases in the sediment, the content of Mg in associated calcite decreases. Conditions in the enclosed lakes appear to be the most favorable for the formation of dolomite relative to calcite. When the deposition of carbonate ceases, halide and sulfate minerals may subsequently precipitate. The precipitation of carbonates appears to be related to the activities of plants that control the chemical composition of the water by photosynthesis. ALDERMAN and VON DER BORCH(1963) visualized a definite pattern in the sedimentation history of the Coorong lagoon and the lakes. Inasmuch as the lakes became isolated from the Coorong lagoon by marine regression, it is possible to assign relative ages to the lakes or groups of lakes. This age in turn seems to delimit the type of sediment and carbonate petrology. The assemblages of minerals that have been recognized by the above two investigators are given in Table XV. This list of assemblages is thought to be in the order of increasing age of the environ-

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

117

TABLE XV SEQUENCE OF MINERAL ASSEMBLAGE IN COORONG LAGOON AND ASSOCIATED LAKES, SOUTH AUSTRALIA

(After ALDERMAN and VON DER BORCH,1963) ~~

Age of lake

111

3

g

.-

I

.1

Mineral assemblage

Approximate Mg/Ca raiio in water ai time of maximum p H

( I ) Aragonite plus magnesian calcite (2) Magnesian calcite (3) Magnesian calcite plus calcian dolomite (4) “Ordered” dolomite (5) Dolomite plus magnesite (6) Aragonite plus hydromagnesite

5 6

8 10 16 20

ment: type I occurs in the Coorong lagoon; type 2 is forming in the most recently isolated lakes in which the absence of aragonite is striking; type 3 occurs in the somewhat older isolated lakes where the amount of calcian dolomite progressively increases with increasing age (in the southern older lakes); and types 4, 5, and 6 occur in the oldest groups of lakes. Considering various geochemical factors, ALDERMAN and VON DER BORCH (1963) found that the relative amounts of Mg and Ca are important in understanding the genesis of the above-described carbonates. They found that a high Mg/Ca ratio of these carbonates is associated with increasing age. The approximate values of the Mg/Ca ratio of water for each group of lakes at the time of maximum pH are shown in Table XV. The above authors suggested that as the waters of each lake approach the saturation level at which NaCl begins to crystallize, the Mg concentration in the water becomes unusually high and calcareous material reacts so as to increase its Mg content. The following reaction series was proposed by Alderman and Von der Borch: aragonite-tmagnesian calcite-tcalcian dolomite+ “ordered” dolomite. (The relationships of dolomite plus magnesite, and aragonite plus hydromagnesite to the above series is not quite clear as yet.) WEBER(1964a) presented the elemental composition of a large group of dolostones and dolomites. It is significant that his more finely grained so-called “primary” dolostones are consistently higher in alumina and some trace elements that would likely be associated with clay minerals. As Weber noted, the so-called “primary” dolostones are in fact probably secondary. One might suspect that the most obvious chemical differences between his so-called “primary” and “secondary” groups are possibly largely due to the differences in energy of the original environment and the relative amounts of carbonate and clay mineral muds that accumulated in the original calcareous sediment. Apart from the significant differences noted by Weber there is a remarkable similarity in trace-element associations for dolo-

118

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

mites and dolostones which tends to confirm the similarity of origin of most dolostones. The latter probably owe their origin to secondary replacement of original calcium carbonate material. Mn, Sr, P, and Cu distribution in sediments of the Russian platform (STRAKHOV et al., 1956)

Most of the following information is based on the work of Russian investigators who accumulated interesting data for the preparation of lithochemical facies maps. In dealing with facies changes, it is not possible to divorce entirely carbonate from terrigenous sediments. On the contrary, it is more illuminating to treat chemical aspects on a comparative basis, showing synchronous variations as well as those reflecting changes through geologic time within the same basin of deposition. In an absence of comparative analytical data illustrating possible regular changes in content of elements with the environment of accumulation, STRAKHOV et al. (1956) used an indirect method by employing the familiar “ideal facies section” to solve the problem. They postulated that the lithologic sequence sandssilts-clays-marls-limestones reproduces the whole range of gradual transition from the near-shore to the basin or pelagic facies. Some objections to this idealization have been raised by RONOVand ERMISHKINA (1959) which are discussed in the next section. In studying ancient sediments that were formed under humid conditions in the geologic past, STRAKHOV et al. (1956) found that in the “ideal facies” section the concentrations of most elements increase on going from sandstones to siltstones to argillites and then diminish toward the pure calcareous deposits. The concentrations of Mn, P, and Sr, however, continue to grow to a maximum in the mads or the argillaceous limestones, and occasionally in the pure carbonates (Fig.8). These investigators mentioned that ten other elements also show a somewhat higher concentration in the carbonate sediments. Hence, it seems that in the platform type of environment many elements preferentially to almost entirely bypass the near-shore zone. Strakhov and co-workers stated that the distribution of elements depends mainly on the mode of transportation and the physicogeographic conditions, and to a lesser extent on the properties of the element. The ratio of amounts of an element in suspension and in solution varies considerably for different elements. For example, Strakhov and his co-workers mentioned that Fe, Mn, P, and a number of minor elements such as V, Cr, Ni, Co, Cu, Pb, Zn, Ga, and others, remain mainly in suspension during transportation by river waters and enter true solution only to a minor extent. Also, within the size range of a suspension, some elements may occur in coarser portions, whereas others may constitute part of the finer components. These differences in mode of element migration in streams are partly responsible for the differentiation of

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

119

3.0 2.o I .o

Fig.8. Distribution of elements in Pashiysk marine sediments of Second Baku. ss=sands; sf =silts; arg=argillaceous sediments; murl=marls; arg Is = argillaceous limestones; Is =limestones. (After STRAKHOV et al., 1956.) The ordinate was not marked in the original article, and the values presented here (%, are assigned by the authors of this chapter. lO-*O,< probably also applies to the lower graph.

elements during sedimentation. The migration of matter in solution tends to favor transportation to the pelagic zones of a basin inasmuch as the maximum contents of significant elements which migrate mainly in solution are found in clay-rich and calcareous basin sediments. When suspensions dominate the mode of transportation, then association of elements with particular size grades becomes more significant, and the maxima on the distribution curves shift toward the coarser nearshore sediments. Elements adsorbed on colloidal matter tend to accumulate in the clay zone, whereas detrital minerals and elements present in their lattices are de-

120

K. H. WOLF. G. V. CHILINGAR AND F. W. BEALES

posited in the silts and sands. In cases where an element migrates both in a lattice of coarser particles and adsorbed on colloidal matter, the curve may have two maxima: one for sand and one for clay deposits. In addition to the suspension/solution ratio and the distribution of elements in the different size grades, geographic factors of element availability are important. Thus, the ultimate element-distribution is affected by the type and intensity of weathering in the source area and degree of sorting during transportation and deposition. Intensive chemical weathering of the source rocks breaks down the complex silicates, alumino-silicates, and sulfides of igneous and metamorphic rocks. The elements thus obtained (Fe, Mn, P, V, Cr, Co, Cu, Pb, Zn, Be, etc.) migrate partly in solution and partly in suspension as adsorbed cations on colloidal particles such as clay minerals, as mentioned above. The more intensive the chemical weathering on the continent, the more impoverished in elements will be the sand- and siltsized sediments. Consequently, there will be a higher concentration of the elements in fine-grained argillaceous-calcareous deep-water sediments. The better sorted sediments usually show a clear maximum on the distribution curve. Poor sorting gives rise to spreading and more uniform element distribution in the various environments. An intensification of chemical weathering in the source area, accompanied by a high degree of sorting, results in an increase of contrast in the distribution of the elements in different lithologies, and in an increase in similarities between the distribution curves of the various elements in lithologically different types of sediments. In other words, the variability in curve shape becomes less and the curves become more comparable and concordant under intense weathering and better sorting conditions (STRAKHOV et al., 1956). “Dilution” of sediments faraway from shore with carbonates results in a decrease in the proportion of elements in marls and carbonate rocks as compared to argillaceous sediments. The content of Sr, however, which is associated largely with carbonates, should increase with increasing carbonate content. Mn distribution in sediments of the Russian platform (RONOV and ERMISHKINA, 1959)

Some objections raised against the use of “ideal facies concept” by STRAKHOV et al. (1956) come from RONOVand ERMISHKINA (1959). As shown in previous sections, STRAKHOV et al. (1956) found that the Mn content of the Lower Frasnian and the Lower Carboniferous rocks of the Second Baku sediments increases from the sands to the limestones. Thus, they concluded that Mn content increases with increasing distance from the shore; that is, it increases with distance from the Mn ore deposits, which Ronov and Ermishkina reported as having been situated along the shores of the ancient shallow seas. Strakhov and co-workers, of course, were well aware that local variations from their “ideal section” could occur. RONOVand ERMISHKINA (1959), however,

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

121

demonstrated more than a local variation and developed the concept further. They analyzed 10,389 samples and obtained the following results: 0.063 % Mn in sands and silts, 0.075 % Mn in clays, and 0.068 % Mn in carbonates. These data are in direct contradiction of the assumption that Mn content increases gradually from the sandstones to the clays and then to the carbonates. It was suggested that this discrepancy was mainly due to the differences of rock types studied by STRAKHOV et al. (1956) and by RONOVand ERMISHKINA (1959). The latter two scientists divided all the types of sediments that had been analyzed into two genetic groups according to the paleoclimatic conditions: first, sediments formed in an arid, hot and dry climate; and second, deposits accumulated in a humid and warm climate. On considering this division, two completely different types of Mn distributions became apparent. In humid zones, such as those studied by STRAKHOV et al. (1956), the Mn concentrations increase continuously from the sands to the clays and further to the calcareous sediments. On the other hand, in arid zone accumulations the Mn content increases from the sands and silts to the clays and then decreases rapidly to a minimum in the carborpte sediments (Fig.9). The changes of the Mn concentration through the stratigraphic column of the Russian platform are given in Fig.10. The sediments of some periods show relative enrichment, whereas others indicate impoverishment in Mn content. The direction of these changes through time are more or less the same for all rock types, but for some intervals the displacement of the maxima and minima reflects the lithology of the sediments. (In this connection it should be remembered that the Mn contents of the Russian platform sediments are considerably smaller than those of geosynclinal sediments. In modern oceanic sediments the Mn content is about 4 times higher than the Mn contents of the Russian platform sediments.) If the lithology and Mn variations are compared, it becomes evident that Mn0 in *I.

0.100

!

0’0201 Sands ;nd siltstones

~

, 0 0

1

Clays

’

Humid zone

Carbonate rocks

’

Fig.9. Variation in MnO content of sedimentary rocks of the Russian platform according to the 1959, fig.1.) climatic conditions of their formation. (After RONOVand ERMISHKINA,

122

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

greater uniformity in Mn contents prevails in the sandstones and siltstones, whereas the fluctuation is a feature of the carbonate rocks. As shown in Fig.11, MnO follows FeO closely in its distribution through the stratigraphic column, indicating that Fe and Mn are genetically related; this has also been noticed by KUDYMOV (1962). The ratio of Mn to Fe remains more or less constant in clays and sands, whereas in carbonate rocks there is generally an increase in the Mn/Fe ratio relative to the associated sands and shales. This suggests that in zones of carbonate formation some regional geochemical processes are operative that lead to some differential separation of Mn and Fe. Local favorable pH and Eh conditions in both the transportation and deposition mediums (KRAUSKOPF, 1957) may cause a nearly complete geochemical differentiation of Mn and MnO in%

Carbonates

0.26-

f

I

0.24.

I

022-

I

0.20

I

018. 0.16

I

A

0.14 .

I

I

0.12 0.10 .

OD8 0.06 .

004 0.02 -

0 690

510

430 Absolute

time

30 in

225

150

m

0

millions of years

Fig.10. Variation in MnO content in sands and silts, clays, and carbonate rocks of the Russian 1959, fig.2.) Explanation of symbols: platform. (After RONOVand ERMISHKINA, snz = Sinian PZ = Upper Permian TI = Lower Triassic Cm = Cambrian Tz = Middle Triassic o = Ordovician s = Silurian T3 = Upper Triassic SI = Upper Silurian JI = Lower Jurassic sz = Lower Silurian Jz = Middle Jurassic J3 = Upper Jurassic DI = Lower Devonian Dz = Middle Devonian Cri = Lower Cretaceous Crz = Upper Cretaceous Di = Frasnian D: = Famennian Ce = Cenozoic Tr = Tertiary c 1 = Lower Carboniferous Pg = Paleogene cz = Middle Carboniferous Ng = Neogene c 3 = Upper Carboniferous PI = Lower Permian Q = Quaternary

123

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

510

690

L30 Absolute

310

time

in

225

150

70

millions of years

Fig.11. Variation in the MnO, FeO, and insoluble residue (I.R.) contents in carbonate rocks of the Russian platform. (After RONOVand ERMISHKINA, 1959, fig.5.) For explanation of the symbols see Fig. 10. Mn 0 in %

Carbonates

A

-f

/ \ I \

0.130

\

Clays

"'":

RWO0.050-

\

/

0.110

'f

, , ,

'-. \ .A

Fig.12. Variation in the MnO content in sedimentary rocks according to the facies conditions of 1959, fig.6.) their formation. (After RONOVand ERMISHKINA,

Fe that would favor the formation of sedimentary manganese deposits. The maximum Mn concentration, independent of lithology, is associated with coastal facies deposits; and Mn content decreases both toward the continental and basinal sediments, as illustrated in Fig.12. On the other hand, if the climatic conditions are taken into consideration, their influence on the facies profile becomes quite clear (Fig.13). Coastal sediments of a humid environment have

124

0.09

K. H. WOLF, G. V. CHlLlNGAR AND F. W. BEALES

-

.

0.08 0.07 . 0.06 .

Humid

zone

e---

0.050.04-

\

'Continental ' lagoonal

ao3. 0.02

and

\,Arid

zone

I

Pelagic

1

Fig.13. Variation in the MnO content in Russian platform deposits according to the facies and 1959, fig.7.) climatic conditions of their sedimentation. (After RONOV and ERMISHKINA,

a higher Mn content than those of similar facies formed under arid conditions. The decrease of Mn concentration toward the continental facies occurs more rapidly in a humid than in an arid zone deposit. On the other hand, the decrease of Mn content toward the pelagic or basin sediments takes place more rapidly in an arid environment as compared to humid ones. These differences are due to different intensities of physicochemical mechanisms that are indicative of various climatic conditions. Deep weathering in the source area results in large amounts of bivalent Mn, which is completely oxidized. The transportation medium is rich in organic acids and permits the Mn to stay in solution for a long time and to migrate beyond the limits of the continental facies. Thus, only small amounts of Mn are precipitated in the latter. The major deposition occurs as soon as the alkaline sea water is encountered. As powerful currents can freshen the sea water to a great distance from the shore, a very gradual gradient from acidic to alkaline conditions can prevail. Thus, the precipitation of the Mn does not occur all at once, but instead may gradually diminish with distance from shore. In arid localities the conditions are quite different. In cases of slight vegetation cover, chemical weathering is slow and shallow, and as a result of absence of organic acids the surface waters are slightly alkaline or neutral. Hence, the small amounts of totally oxidized bivalent Mn ions are not readily transported in solution. Because of smaller amounts of fresh-water run-off in arid regions, the sea water is not diluted to a great extent; and any Mn that reaches the sea in solution is rapidly precipitated in coastal and near-shore alkaline environments. RONOVand ERMISHKINA (1959) further pointed out that the rate and degree of upheaval of the continent controls the amount and rate of fresh-water run-off, which in turn is changing the width of the zone of Mn deposition along the coastline. For regional changes in contents of the elements Fe, Mn and P from siltstones to clays and marls, see also the publication of TIKHOMIROVA (1964).

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

125

Phosphate distribution in sediments of the Russian platform (RONOVand KORZINA, 1960)

The phosphate content of the Russian platform sediments was investigated by RONOVand KORZINA(1960), who found that geosynclinal phosphorites have a higher content of both PzO5 and carbonates than those of the platforms. In contrast, the phosphorites of the platform deposits are richer in terrigenous detritus. The average PzO5 content of sandstones, clays, and carbonates of the Russian platform is 0.104 %, 0.102 %, and 0.068 %, respectively. Significant for determining the mode of origin of phosphorites is the fact that the distribution of dispersed P in carbonate rocks follows the pattern of organic carbon. The curves in Fig.14 show an enrichment in PzO5 and Corgduring 0,D3, and J3 and an impoverishment during Snz, S,C, P, and Cr2 times. Most of the living organisms are concentrators of phosphorus; the PzO5 content in marine plankton, for example, is a thousand times greater than that in sea water. After death, diagenetic processes, such as those caused by bacterial decomposition, break down the P-bearing organic material and the phosphate formed goes into solution (RONOVand KORZINA,1960). As a result of diagenetic redistribution of PzO5 in the sediments, the phosphorus is precipitated around minute nuclei such as skeletons to form nodules of phosphorite. It seems that the larger the amount of organic matter present, the more phosphorus will accumulate in the calcareous ooze. It is not clear, however, if this phosphorus is released as a result of decay of the organic matter or precipitated by organic reagents formed during decay processes, or both. 5'2' inoh

Corg

in %

0.22 0.33

0.18 0.16

0.10 0.06

on2 0 Absolute

time

in

millions

of years

Fig.14. Variations in the average content of PZOSand Corg.in the carbonate rocks of the Russian platform. For explanation of the symbols see Fig.10. (After RONOVand KORZINA,1960, fig.5.)

126

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

in%

mela

1.4 . 0.26 '

A

1.2 0.221.0 0.19 '

0 8 . 0.16 .

0.6 . 0.12 Humid zone

0 . 4 . 0.08.

'

0.2- 0.04-

*------

/

- _-

/----

1

'SandstoAes and si It st on es

'

I Claystbnes

5%

Humid zone Cog. \.Arid zone -*Arid zone

$05

cots.

'

CarboAate

rocks Fig.15. Variation in the average PZOSand Corg.contents in sandstones, claystones and carbonate rocks of the Russian platform deposited in humid and arid climatic zones. (After RONOVand KORZINA, 1960, fig.9.) con inel

5in%s

1.3

1.2

024

1.1

0.22-

1.0

0.20-

09

0.18 .

08

0.16

0.7

014 .

0.E

0.12 .

0.5

0.10

0.4

0.08 -

0.3

0.06-

~

Humid zone cog, Humid ZOMP205

.

. /

\

----.

em-----

0.2

0.04 -

0.1

0.02

0

c/--

I Nearshoic

\

\.Arid

zone

5%

Arid zone coq.

_ / - _

Continental and lagoonal

\

-

marine

I

Pelagic

I

Fig.16. Variation in the average PZOSand Corg.contents in the sedimentary rocks of the Russian platform according to the facies and the climatic conditions of deposition. (After RONOVand KORZINA,1960, fig.11.)

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

127

Ronov and Korzina divided the sandstones, shales and carbonates according to their mode of formation into arid and humid zone deposits; and as to their environment of deposition, into continental, nearshore and pelagic facies (Fig. 15 and 16). It is interesting to note that in sandstones and siltstones there is no obvious correlation between dispersed phosphorus and organic carbon. The occurrence of P is determined by different factors which include: (I) accumulation of detrital “terrigenous” apatite derived from igneous rocks in the source area; (2) cementation of porous arenaceous sediment with phosphate, brought to the site of precipitation by the upwelling of water from deeper parts of the basin; and (3) admixture of phosphatic shells, such as those of inarticulate brachiopods. A1 and Ti distribution in Russian platform sediments (MIGDISOV, 1960)

The A1 and Ti distribution in the sediments of the Russian platform have been examined by MIGDISOV (1960). The variation of the Ti02 concentration in the carbonate rocks in the geologic column parallels those of the A1203, SiOz, and the content of insoluble residue in carbonates (Fig.17). As pointed out by Migdisov,

Fig.17. Variation of the average contents of insoluble residue (I.R.), SiOz, A1~03,and Ti02 in the carbonate rocks of the Russian platform with time. For explanation of the symbols see Fig.10. (After MIGDISOV,1960, fig.5.)

128

K. H. WOLF, G . V. CHILINGAR AND F. W. BEALES

the clays of humid epochs in general have higher average A1 and Ti contents. The maxima of the TiOz/A1203 ratios correspond to humid periods, during which intensive chemical weathering occurred with the formation of a thick weathered overburden and the deposition of large amounts of kaolinite, bauxite and clean quartz sand. The Ti and A1 are associated with the insoluble residue in the carbonate rocks and their content is determined by the tectonism of the platform. The maximum Ti02 concentration occurs in sediments formed at the beginning and the end of each tectonic cycle; this corresponds to both transgression and regression and an associated intensive supply of detritus. Element distribution as revealed by KUDYMOV (1962)

The distributions of minor elements on a regional scale and through the geologic column of the Russian platform (KUDYMOV, 1962) are of particular interest because of their application to both correlation and environmental reconstructions. As most of the findings are in close harmony with the geochemical findings discussed in the previous sections, there is no need to review them in detail here. It is sufficient to state that the spectral curves of Ca, Mg, Al, and Si, taken together, reflect the basic lithologies; and one can quite readily discriminate between limestones, dolomites, sandstones, shales, marls, argillaceous limestones, calcian dolomites, dolomitic marls, and calcareous or dolomitic shales. In general, a change from shales and sandstones into calcareous rocks is indicated by a decrease of Na, B, Fe, Mn, Ti, Cr, and P contents; Ca, Mg, and Cu contents, however, do not decrease. In addition, V, Ni, and Cu are usually associated with argillaceous sediments. It is believed that some of the Cu has been derived from organisms that are capable of concentrating this element. Cu and Ni are genetically related, especially in sandstones and shales. The Mn content relative to Cu is on the average higher in carbonates than it is in siltstones and shales. This suggests that there is no genetic relation between these two elements. Based on extensive research, KUDYMOV (1962) found that, as a rule, lithologically uniform sedimentary bodies are not geochemically homogeneous. In fact, some of the upper parts of formations are spectrographically similar to the lower parts of overlying deposits. Hence, the accepted lithologic boundaries are often transgressed by geochemical boundaries. Environmentally induced niineralogic and chemical changes of cement and concretions

BROVKOV (1 964) described diagenetically formed carbonate cement types and concretions as a product of different environments in the Jurassic coal measures. These are predominantly composed of terrigenous siltstones, sandstones, conglomerates and coals, and rare small lenses of pelecypod-rich limestones. The trends of the p H and Eh changes during diagenesis at any one locality, as

-

129

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

R

I 1 I

Siderite

D

L

T

LG

DS

SS

m

Silica

3

Pyrite An ke r i t e Calcite

.\.

Res. org. C

N

Fig.18. Occurrence of the various phases in the various types of facies. R = river beds; D = deltas; L = lagoons; LG= lagoon-gulfs; T= talus sands; SS= shallow sea deposits; DS= deep-sea clays. (After BROVKOV,1964, fig.7.)

'18

50

*\

\

\

\

LO

\

\

\

\

\

\

30

'. /=

/'

20

10

/

/

/

/

\

alcite

\

---

d'

IC)

\

/

_------, \

/

K -

/

-- -

.

-0

0 '' 0

Siderlte IS) Quartz

IQ)

0

Q

A

Q

A with si deri t e

A

and

wirh Q siderite

A

C with siderite

Zones of diagenetic formation

Fig.19. Authigenic zones and relative proportions of quartz and carbonates in the cement of sandstones-siltstones of various facies. Q = quartz; A = ankerite; C = calcite, (After BROVKOV, 1964, fig.9.)

130

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

Fig.20. Occurrence of different types of concretions in the various facies. R = river beds; D = deltas; M = marshy lakes; LG= lagoon-gulfs; L= lagoons; T= talus sands; SS = shallow sea deposits; DS= deep-sea clays. (After BROVKOV, 1964, fig.9;sideroplesite = Mg-rich siderite.)

well as from facies to facies, have been suggested through the study of calcite, siderite, sideroplesite, ankerite, dolomite, authigenic quartz, pyrite, and glauconite. The distribution of the numerous phases is given in Fig.18; authigenic zones and relative amounts of diagenetic quartz and carbonate cement of the sandstones and siltstones of various facies are presented in Fig. 19; and the distribution of different mineralogic types of concretions in the various facies is shown in Fig.20. Metamorphically mobilized elements An interesting use of trace elements in connection with low-grade metamorphosed sediments was suggested by GORLITSKIY and KALYAEV (1962), and others prior to them. As soon as more information is available on the distribution pattern of syngenetic elements in sediments, it should be possible, even if only indirectly, to follow the migration of trace elements during metamorphism. Gorlitskiy and Kalyaev observed: (I) a distinct increase in trace-element content in the schists, which they considered as having been formed from argillaceous sediments; (2) a reduction in trace-element content in quartzites and sandstones; and (3) a still greater reduction in content of trace elements in the dolomites. Ba and Sr are noteworthy in this respect. They were probably originally deposited with the carbonate sediments, but appear to have migrated with some of the carbonates to form cement in the sandstones and quartzites.

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

131

WORLD-WIDE CHANGES IN COMPOSITION OF CARBONATES THROUGHOUT GEOLOGIC TIME

In the previous section a number of examples have been given that illustrate changes in elemental composition both in synchronous sediments and through the geologic column within the Russian platform. No consideration was given to the fact that some of the changes in contents of elements occurring from the Precambrian to the Recent may be world-wide. The interpretations of the causes are quite hypothetical and consequently are of a controversial nature. VINOGRADOV and RONOV(1956) mentioned that the composition of the carbonate sediments of the Russian platform show a periodicity and a definite trend through geologic time, which are comparable to those observed on the North American continent. As shown in Fig.21, with a decrease in geologic age the Mg content diminishes twenty-five fold from 12.63 % in the Proterozoic to 0.51 % in the Quaternary. This is accompanied by a conspicuous increase in Ca content of carbonate rocks from the Proterozoic (20.35 %) to the Quaternary (35.9 %). Fig.22 demonstrates similar trends in North America as based on the Ca/Mg ratio. According to VINOGRADOV and RONOV(1956), the dolomites of the Russian platform are syngenetic and/or early diagenetic, and the Ca and Mg contents consequently reflect the geochemical processes occurring at or close to the sea floor. It is important to note here the conclusions of TEODOROVITCH (1960, p.76) that: ( I ) during the Precambrian and Early Paleozoic times most of the dolomites resulted from direct chemical precipitation out of sea water; (2) dolomites of the Late Paleozoic time are of chemical (primary dolomites in salinified lagoons or brackish-water large bays) as well as of diagenetic origin; and (3)during the Meso-

Absolute time in millions of years

Fig.21. Variation with time of the average percentages of Ca and Mg in the carbonate rocks of the Russian platform. For explanation of the symbols see Fig. 10. (After VINOGRADOV and RONOV, 1956, fig.3.)

132

K. H. WOLF, G. V. CHILINGAR AND F. W. BEALES

Cahg

+Caledonian

--MHercynian ---w A t p i c e 4

'O0I 90

70

501 40

1

/

30

platform

20 101

0

Sn2

' C m ' S, ' 5 $ D ' C

5x)

Absolute

433

time

310

in

' P ' T ' J ' C r Ce' 225 150 70 0

millions of

years

Fig.22. Variation of the Ca/Mg ratio with time in the carbonate rocks of the Russian platform and and North America (N.A.). For explanation of the symbols see Fig.10. (After VINOGRADOV RONOV,1956, fig.4.)

zoic and Cenozoic periods predominantly diagenetic dolomites were formed. The distribution of Sr is also quite distinct. As has been shown earlier, Sr can enter the aragonite of organisms, and thus the skeletal carbonate sediments are enriched in Sr content. Sr can also precipitate with marine salts together with CaC03, either independently or together with CaS04. The data on the Sr con-

0.18- 18

0.16: 0.14.

14 1 61

0.12-

0.10. 0.08

0.06

0.04, 0.02.

0-

Absolute

time

in

millions

of years

,

Fig.23. Variation with time of the average percentages of CaS04 and Sr. For explanation of the and RONOV,1956, fig.5.) symbols see Fig.10. (After VINOGRADOV

133

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

centration in the carbonate rocks indicate certain maxima that coincide with maxima of CaS04 contents. Lower Paleozoic deposits have a small CaS04 content, and the Sr concentration is also correspondingly small. In Middle and Upper Paleozoic times the amounts of both CaS04 and Sr increase (Fig.23). This parallelism in composition, however, is not present from the beginning of the Mesozoic: CaS04 in the carbonate rocks is practically zero, whereas the Sr content increases rapidly. This trend is well demonstrated by the change in Ca/Sr ratio with time as shown in Fig.24. The superimposed curve for the North American carbonate rocks illustrates a similar increase in Sr content. There is an almost fifty-fold enrichment of Sr from the Proterozoic to the Tertiary. (See FAIRBRIDGE, 1964, for further discussion.) Complementary to the observed changes in Ca and Mg contents in carbonate sediments from the Proterozoic to the Tertiary, there are similar trends in the argillaceous sediments and sandstones. There is a distinct increase in the Ca/Mg ratio with decreasing age. The Ca and Mg contents in both sandstones and clays are probably largely associated with carbonate admixture. A similar tendency toward an increase in the Ca/Mg ratio with decreasing age has been reported from the carbonate fraction of phosphorites (RONOVand KORZINA,1960). VINOGRADOV and RONOV(1956) pointed out that although there is a distinct relationship between the lithology and the content of certain essential elements (e.g., Mg in dolomite), the changes in content of elements through the geologic column are also quite distinct in cases where the elements are only of secondary importance, as in the cements of sediments. This suggests that the initial material of the sedimentary rocks had a common source and that their composition reflects changes in geologic times. They concluded that the general increase in Ca/Mg ratio with

510

L30

Absolute

310 time in

225

M)

70

0

millions of years

Fig.24. Variation with time of the Ca/Sr ratio in the carbonate rocks of the Russian platform and and RONOV, North America (N.A.). For explanation of the symbols see Fig.10. (After VINOORADOV 1956, fig.6 and 7.)

134

WOLF, G.

K. H.

V. CHILINGAR AND F. W. BEALES

time in clays, sandstones, and carbonates, and possibly the Sr content in the latter, in Russia and North America appears to reflect the evolution of the chemical composition of the sedimentary crust. (For additional curves based on the work of VINOGRADOV et al., 1952, see summary of CHILINGAR, 1957.) Additional concepts that attempt to explain the trend of Ca/Mg ratio through geologic times are given by CHILINGAR (1953, 1956a), CHAVE(1954a, b), and FAIRBRIDGE (1957, 1964). Fairbridge discussed some of the problems of interpreting this geochemical trend. RONOV(1959) pointed out that the principal cations in sea water (Na, K, Mg, Ca, Sr, etc.) and the elements of sedimentary rocks (Si, Al, Fe, Ca, Mg, Na, K, Mn, etc.) were derived in the past from the erosion of ancient rocks. Although the water of the oceans contains the principal anions (CI, S 0 4 , F, B, etc.) and COZ,the same components in the sedimentary rocks and a considerable part of the atmospheric gases (Nz,COz, etc.) must have been derived from an additional source, most likely from volcanism (RONOV,1959). According to RONOV(1959), if RUBEY'Sview (1955) is maintained that the amounts of COz in the atmosphere and ocean remained relatively constant and that the excess volatiles supplied through volcanism accumulated gradually, "then the conclusion is inevitable that, in order for these conditions to persist, in the system atmosphere-ocean there must have been a continuously active mechanism of removal and fixation of COz . ." Ronov proceeded to compare the evidence of volcanism during the geologic epochs and periods with the amount of COz locked in the sediments as carbonates. A possible relationship between the volumes of volcanic emanations and the

.

9.75

825 6.75

E

=

m x

5.25

E 3.75

I

al

E

3

225

t

\

C%of the carbonates

\

P

s

0.75 1

,

I

D I ' D Z ' D '~ c1

310

275

'

I

c2+3

Absolute

'

PI

225 time

I

in

'

,

I

I

I

,

T1 I T 2 ' T 3 ' J1 ' J21J3' 185 150 110 millions of years

p2

Fig.25. Relation between the volumes of subaqueous and subaerial volcanic extrusions, and the volumes of COZlocked in the carbonate rocks of the present-day continents. For explanation of the symbols see Fig.10. (After RONOV,1959, fig.1.)

ELEMENTAL COMPOSITION OF SEDIMENTARY CARBONATES

Absolute

time

135

in millions of years

Fig.26. Relation between volumes of volcanic extrusions and areas covered by seas (percentage of the total of the present-day continents). For explanations of the symbols see Fig.10. (After RONOV,1959, fig.2.)

amounts of COZ locked in carbonate sediments is illustrated in Fig.25. The volcanic COZ added to the atmosphere and sea water was apparently almost immediately incorporated in the carbonate sediments deposited. Deviations from this pattern must have been rare and of short duration, as an increase in the amount of COZ would have dissolved carbonates. RONOV(1959) also mentioned that the epochs of intensive volcanism and great accumulation of carbonates alternated with periods having less intense volcanic activity. The fluctuations correspond well to marine transgressions and regressions (Fig.26). Ronov concluded that ". . . the periodic fluctuations in the amount of carbonate sediments were governed by the corresponding periodic changes in the intensity of the interrelated volcanic and tectonic (epeirogenic) processes. The former provided the quantity of C02 needed for the accumulation of the carbonates; the latter determined the area of the inland seas. . ." The question whether or not the absolute amount of COZin the atmosphere and oceans changed during post-Precambrian (Phanerozoic) time can be approached indirectly by investigating the lithology and chemical composition of the sedimentary deposits. In particular the Ca/Mg ratios in carbonate rocks may serve as a kind of COZ indicator in the system atmosphere-ocean (CHILINGAR, 1956a; RONOV,1959). This is possible if, first of all, the much higher Mg concentration and the high COZcontent in the water, in addition to climatic conditions and salinity, govern dolomite formation. Ronov concluded that during Paleozoic time the pcoZ decreased very slowly. At the end of the Mesozoic, however, it diminished

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more rapidly because of the precipitation of carbonates associated with the vast accumulation of Globigerina ooze during the Upper Cretaceous and Paleocene times, and because of photosynthetic fixation by plants. In addition to the control of the C02 budget by volcanism, one has to consider the effect of organic life processes. Apart from possible minor catastrophies of individual taxonomic groups, it is reasonable to assume that animals and plants have been establishing a progressively greater control on-their environment. It is not likely, for instance, that carbon dioxide concentrations in the atmosphere have fluctuated greatly for any considerable period. Simple mutational probability demands that plants must have become progressively more efficient in such a basic activity as the utilization of carbon dioxide. Furthermore, it is likely that the vast mass of the slowly evolving oceanic plankton has controlled the C02 budget more than their more flamboyant and variable terrestrial relatives. Ultimately it should be possible to relate the composition of sediments to organic evolution and its interplay with the earth’s and cosmic evolution.

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SUGAWARA, K., OKABE,S. and TANAKA, M., 1961. Geochemistry of molybdenum in natural waters (11). J. Earth Sci., Nagoya Univ., 9: 114128. M. W. and FLEMING, R. H., 1952. The Oceans, 4 ed. Prentice-Hall, SVERDRUP, H. U., JOHNSON, Englewood Cliffs, N.J., 1087 pp. SWAN,E. F., 1956. The meaning of strontium/calcium ratios. Deep-sea Res., 4: 71. S W E ~K., , 1965. Dolomitization, silification and calcitization patterns in Cambro-Ordovician oolites from northwest Scotland. J. Sediment. Petrol., 35: 928-938. TAFT, W. H., 1962. Influence of magnesium on the stability of aragonite, high-Mg calcite, and vaterite, and its control on the precipitation of aragonite. Trans. Am. Geophys. Union, 43: 477 (Abstract). TAFT,W. H., 1967. Physical chemistry of formation of carbonates. In: G. V. CHILINGAR, H. J.BIsSELL and R. W. FAIRBRIDGE (Editors), Carbonate Rocks, B. Elsevier, Amsterdam, pp. 151-167. TAFT,W. H. and HARBAUGH, J. W., 1964. Modern carbonate sediments of southern Florida, Bahamas, and Espiritu Santo Island, Baja California: a comparison of their mineralogy and chemistry. Stanford Univ. Publ., Univ. Ser., Geol. Sci., 8: 1-133. TASCH, P., 1957. Fauna and paleoecology of the Pennsylvanian Dry Shale of Kansas. In: H. S. LADD(Editor), Treatise on Marine Ecology and Paleoecology. 2. Paleoecology-Geol. Soc. Am., Mem., 67: 365406. TATSUMOTO, M. and GOLDBERG, E. D., 1959. Some aspects of the marine geochemistry of uranium. Geochim. Cosmochim. Acta, 17: 201-208. TAYLOR, J. H., 1964. Some aspects of diagenesis. Advan. Sci., 23: 417-436. TEICHERT, C., 1930. Uber die Moglichkeit der syngenetischen Entstehung einiger Metallsulfide in Kalken durch die Konzentrierende Tatigkeit der Organismen. Zentr. Mineral., Abt. B, 1930: 49-70. TEODOROVICH, G. I., 1955. Uber die Genesis des Dolomits in sedimentaren Bildungen. Z. Angew. Geol., 2: 91-93. TEODOROVICH, G. I., 1960. About origin of dolomite. Sov. Geol., 1960(5): 74-87. TEODOROVICH, G. I., SOKOLOVA, N. N., ROWNOVA,E. D. et BAGDASSAROVA, M. V., 1964. Traits particuliers mineralogiques-geochimiques de l'assise terrigene du carbonifere (Editor), inferieur dans la region Ouralienne-Volgienne. In: L. M. J. U. VAN STRAATEN Deltaic and Shallow Marine Deposits. Elsevier, Amsterdam, pp.399409. THOMPSON, T. G. and CHOW,T. J., 1955. The Sr/Ca atom ratio in carbonate-secreting marine organisms. Deep-sea Res., 3 (Suppl. Papers Marine Biol. Oceanog.) : 20-30. TIKHOMIROVA, E. S., 1964. Distribution of iron, manganese and phosphorus in the Lower Oligocene deposits of Mangyshlak. Dokl. Akad. Nauk S.S.S.R., 143: 143-145. TISCHENDORF, G. und UNGETH~~M, H., 1965. Zur Anwendung von Eh-pH Beziehungen in der geologischen Praxis. Z. Angew. Geol., 11 : 57-67. TUREKIAN, K. K., 1955. Paleoecological significance of the Sr/Ca ratio in fossils and sediments. Bull. Geol. SOC.Am., 66: 155-158. TUREKIAN, K. K., 1957. The significance of variations in the strontium content of deep-sea cores. Limnol. Oceanog., 2: 309-314. TUREKIAN, K. K., 1959. Factors controlling the traceelement concentration in Recent and fossil molluscan shells. Geol. SOC.Am., Abstr., 70: 1960. TUREKIAN, K. K., 1963. The use of trace-element geochemistry in solving geologic problems. In: D. M. SHAW(Editor), Studies in Analytical Geochemistry-Roy. SOC. Can., Spec. Publ., 6: 3-24. TUREKIAN, K. K., 1964. The marine geochemistry of strontium. Geochim. Cosmochim. Acta, 28: 1479-1496. TUREKIAN, K. K. and ARMSTRONG, R. L., 1960. Magnesium, strontium, and barium concentrations and calcite/aragonite ratios of some recent molluscan shells. J. Marine Res., 18: 133-151. TUREKIAN, K. K. and ARMSTRONG, R. L., 1961. Chemical and mineralogical composition of fossil molluscan shells from the Fox Hills Formation, South Dakota. Bull. Geol. SOC.Am., 72: 1817-1828. TUREKIAN, K. K. and KULP,J. L., 1956. The geochemistry of strontium. Geochim. Cosmochim. Acta, 10: 245-296.

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TUREKIAN, K. K. and WEDEPOHL, K. H., 1961. Distribution of the elements in some major units of the earth's crust. Bull. Geol. SOC.Am., 72: 175-191. USDOWSKI, H.-E., 1962. Die Entstehung der Kalkoolitischen Fazies des norddeutschen Unteren Buntsandsteins. Beitr. Mineral. Petrog., 8: 141-179. USDOWSKI, H.-E., 1963a. Die Genese der Tutenmergel oder Nagelkalke (cone-in-cone). Beifr. Mineral. Petrog., 9: 95-1 10. USDOWSKI, H.-E., 1963b. Der Rogenstein des norddeutschen Unteren Buntsandsteins, ein Kalkoolith des marinen Faziesbereichs. Fortschr. Geol. Rheinland Wesffalen, 10: 337-342. USDOWSKI.H.-E., 1964. Dolomit im System Ca2+-Mgz+-C032+-C122--H20. Naturwissenschafen, 51(15): 357. VALENTINE,J. W. and MEADE,R., 1961. California Pleistocene paleotemperatures. Univ. Calif. (Berkeley) Publ. Geol. Sci., 40(1): 1 4 6 . VANNEY, J.-R., 1965. etude sedimentologique du Mor Bras, Bretagne. Marine Geol., 3: 195222. VINOGRADOV, A. P., 1953. The Elemental Chemical Composition of Marine Organisms. Yale Univ. Press, New Haven, Conn., 647 pp. T. F., 1945. On the geochemistry of strontium. VINOGRADOV, A, P. and BOROVIK-ROMANOVA, Dokl. Akad. Nauk S.S.S.R., 46: 193-196. VINOGRADOV, A. P. and RONOV,A. B., 1956. Composition of the sedimentary rocks of the Russian platform in relation to the history of its tectonic movements. Geochemistry (U.S.,S.R.) (English Transl.), 1956(6): 533-559. VINOGRADOV, A. P., RONOV,A. B. and RATYNSKIY, V. M., 1952. Variation in chemical composition of carbonate rocks of the Russian platform (with time). Izv. Akad. Nauk S.S.S.R., 1957.) Geol. Ser., 1961 : 33-50. (In Russian. See CHILINGAR, VONDER BORCH,C., 1965. The distribution and preliminary geochemistry of modern carbonate sediments of the Coorong area, South Australia. Geochim. Cosmochim. Acta, 29: 781800. VONENGELHARDT, W., 1936. Die Geochemie des Bariums. Chem. Erde, 10: 187-246. VONENGELHARDT, W., 1961. Zum Chemismus der Porenlosung der Sedimente. Bull. Geol. Znst. Univ. Uppsala,40: 189-204. WALKER, C. T., 1964.Paleosalinity in Upper Visean Yoredale Formation of England-geochemical method for locating porosity. Bull. Am. Assoc. Petrol. Geologists, 48: 207-220. WANGERSKY, P. J. and GORDON, D. C., 1965. Particulate carbonate, organic carbon, and Mn2+ in the open sea. Limnol. Oceanog., 19: 544-550. WANGERSKY, P. J. and JOENSUU, O., 1964. Strontium, magnesium, and manganese in fossil foraminifera1 carbonates. J. Geol., 72: 477482. WATABE, N. and WILBUR, K. M., 1960. Influence of the organic matrix on crystal types in molluscs. Nature, 188 (4747): 334. WATTENBERG, H. und TIMMERMANN, E., 1938. Die Loslichkeit von Magnesiumkarbonat und Strontiumkarbonat in Seewasser. Kiel Meeresforsch., 2: 81-94. WEBB,D. A. and FEARON, W.R., 1937. Studies on the ultimate composition of biological material. 1. Aims, scope and methods. Sci. Proc. Roy. Dublin SOC.,Ser. A, 21: 487-504. WEBER,J. N., 1964a. Trace-element composition of dolostones and dolomites and its bearing on the dolomite problem. Geochim. Cosmochim. Acta, 28: 1817-1868. WEBER,J. N., 1964b. Chloride ion concentration in liquid inclusions of carbonate rocks as a possible environmental indicator. J. Sediment. Petrol., 34: 677-679. WEBER,J. N. and LA ROCQIJE,A., 1963. Isotope ratios in marine mollusk shells after prolonged contact with flowing fresh water. Science, 1421: 1666. WEDEPOHL, K. H., 1960. Spurenanalytische Untersuchungen an Tiefseetonen aus dem Atlantik. Ein Beitrag zur Deutung der geochemischen Sonderstellung von pelagischen Tonen. Geochim. Cosmochim. Acta, 18: 200-232. WEDEPOHL, K. H., 1964. Untersuchungen am Kupferschiefer in Nordwestdeutschland. Ein Beitrag zur Deutung der Genese bituminoser Sedimente. Geochim. Cosmochim. Acta, 28: 305-364. WICKMAN, F. E., 1945. Some notes on the geochemistry of the elements in sedimentary rocks. Arkiv Kemi, Mineral. Geol., 19B(2): 1-7.

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WILBUR,K. M., 1960a. Shell structure and mineralization in molluscs. In: R. F. SOGNAESS (Editor), Calcification in Biological Systems. Am. Assoc. Advan. Sci., Washington, D.C., pp. 1540. K. M. and WATABE, N., 1960. Influence of the organic matrix on crystal type of molluscs. WILBUR, Nature, 188: 334. WILBUR, K. M. and WATABE, N., 1963. Experimental studies on calcification in molluscs and the alga Coccolithus huxleyi. Ann. N.Y. Acad. Sci., 109: 82-112. WILLIAMS, R. P., 1953. Metal ions in biological systems. Biol. Rev. Cambridge Phil. Soc., 28: 381415. WILSON, R. L. and BERGENBACK, R. E., 1963. Observations on present-day carbonate environments in the Bahama Islands. J. Tenn. Acad. Sci., 38: 31-36. WISEMAN, J. D. H., 1964. Rates of sedimentation of nickel, cobalt, copper, and iron on the equatorial mid-Atlantic floor, and its bearing on the nature of cosmic dust. Nature, 202: 1286-1288. F. J., 1965. Sedimentology of the Lias (Lower Jurassic) of South Wales. J. Sediment. WOBBER, Petrol., 35: 683-703. WOLF,K. H., 1963a. Syngenetic to Epigenetic Processes, Paleoecology, and Classification of Limestones; in Particular Reference to Devonian Algal Limestones of Central New South Wales. Thesis, University of Sydney, Sydney, N.S.W. Unpublished. WOLF, K. H., 1963b. Limestones. Australian National Univ., Canberra, A.C.T. Unpublished. WOLF,K. H., 1965a. Petrogenesis and paleoenvironment of Devonian algal limestones of New South Wales. Sedimentology, 4: 1 13-1 78. WOLF,K. H., 1965b. “Grain-diminution” of algal colonies to micrite. J. Sediment. Petrol., 35: 420-427. WOLF,K. H., 1965c. Gradational sedimentary products of calcareous Algae. Sedimentology, 5: 1-37. WOLF,K. H., 1965d. Littoral environment indicated by open-space structures in algal limestones. Palaeogeography, Palaeoclimatol., Palaeoecol., 1: 183-223. J. R., 1965. Petrogenesis and paleoenvironment of limestone lenses WOLF,K. H. and CONOLLY, in Upper Devonian red beds of New South Wales. Palaeogeography, Palaeoclimatol., Palaeoecol., 1 : 69-1 1 1. WOLF, K. H., EASTON,A. J. and WARNE,S., 1967. Techniques of examining and analyzing H. J. BISSELL and R. W. carbonate skeletons, minerals, and rocks. In: G. V. CHILINGAR, FAIRBRIDGE (Editors), Carbonate Rocks, B. Elsevier, Amsterdam, pp. 253-341. WOODRING, W. R., 1954. Conference on biochemistry, paleoecology, and evolution. Proc. Natl. Acad. Sci., 40: 219-224. F., 1957. Preciptiation of calcite and aragonite. J. Am. Chem. Soc., WRAY,J. L. and DANIELS, 79: 2031-2034. WYLLIE,P. J. and TUTTLE,0. F., 1959. Melting of calcite in the presence of water. Am. Mineralogist, 44: 453459. YUSHKIN,N. P., 1962. The geochemistry of strontium and barium during sulphur deposition. Geochemistry (U.S.S.R.) (English Transl.), 1960(12): 1231-1244. ZARITSKIY, P. V., 1965. Isomorphous entry of CaC03 into siderite and magnesian siderite concretions of the Donbas. Dokl. Earth Sci. Sect. (English Transl.), 155(1965): 151-154. ZELLER,E. J. and WRAY,J., 1956. Factors influencing precipitation of calcium carbonate. Bull. Am. Assoc. Petrol. Geologists, 40: 140-152. ZEN,E-AN, 1959. Mineralogy and petrography of marine bottom samples off coast of Peru and Chile. J. Sediment. Petrol., 29: 513-539. ZOBELL,C. E., 1957. Bacteria. In: H. S. LADD(Editor), Treatise on Marine Ecology and Paleoecology. 2. Paleoecology-Geol. SOC.Am., Mem., 67: 693-698.

Chapter 3 PHYSICAL CHEMISTRY O F FORMATION O F CARBONATES WILLIAM H. TAFT

Department of Geology, University of South Florida, Tampa, Fla. (U.S.A.)

SUMMARY

Modern, unconsolidated, carbonate sediments are composed predominantly of metastable carbonate minerals, whereas ancient carbonate rocks are made up of calcite and dolomite. If ancient carbonates were predominantly metastable prior to lithification, then in order to preserve the original textures solid-state recrystallization must have been operative instead of solution-reprecipitation of aragonite to calcite. Aragonite in contact with distilled water completely recrystallizes to calcite in approximately 100 days at 23°C. Recrystallization rate of aragonite to calcite increases with increasing concentration of calcium ions and increasing temperature. Magnesium, on the other hand, retards recrystallization of aragonite to calcite if the weight ratio of aragonite to magnesium is 804 or less.

INTRODUCTION

One of the more important aspects of carbonate rock formation is that dealing with their chemical origin. Although physical characteristics of carbonate rocks have been extensively studied (BATHURST,1959; HARBAUGH, 1960; MURRAY, 1960; CAROZZI, 1961;and many others), seemingly little progress has been made in deciphering their chemical history. The sites of modern carbonate sediments that are forming and accumulating in many warm, shallow, tropical and subtropical seas, such as the Bahama Banks, Florida Bay, Persian Gulf, and the Great Barrier Reef of Australia, are not unlike those in which sediments of ancient limestones were deposited. One critical aspect of unconsolidated modern carbonate sediments that should be kept constantly in mind, when one considers the origin of carbonate rocks, is their mineralogy. Modern, shallow warm-water carbonate sediments are composed predominantly of metastable carbonate minerals, aragonite and high-magnesium calcite, and contain only minor amounts of low-magnesium calcite (STEHLIand HOWER,1961; Blackman, in CLOUD,1962; TAFTand HARBAUGH, 1964). Carbonate rocks are composed essentially of two stable minerals, calcite and dolomite. One

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of the problems facing chemists and geologists alike is the abundance of metastable carbonate minerals in modern sediments and their absence in carbonate rocks. Only in rare instances, however, one can demonstrate recrystallization of metastable carbonate minerals to either calcite or dolomite. These exceptions include beach rock exposed to fresh water in the form of ground water or rainfall (DEBOO, 1961; RUSSELL, 1961) and dolomite replacing aragonite (ILLING, 1964; LUCIAet al., 1964; SHINNand GINSBURG, 1964).One notable exception to the apparent rule of lack of persistence of exposed metastable carbonate minerals can be found in a report by DURHAM (1950), in which he described metastable high-magnesium calcite surviving at the expense of calcite in uplifted Pleistocene carbonate sediments along the Peninsula of Lower California (Baja California, Mexico). One may summarize this introduction to the problem as follows: ( I ) Most modern, unconsolidated, shallow warm-water carbonate sediments are composed of metastable minerals. (2) Metastable carbonate minerals are generally absent in Pliocene and.older carbonate rocks. (3) If one can assume that Pliocene and older limestones were chiefly metastable carbonate minerals originally, virtually all limestones have undergone recrystallization. ( 4 ) Recrystallization can be either a solid-state recrystallization or can be achieved through the solution of metastable carbonate minerals and reprecipitation as stable carbonate forms. (5) Many older limestones show preservation of very delicate structures, which is probably due to the early lithification that prevented compaction from destroying these textures. (6) Modern carbonate sediments, for the most part, tend to be unconsolidated. This possibly suggests that either rates of lithification have changed since older limestones formed, or chemical environments at present are not conducive to lithification. The origin of carbonate rocks is extremely complex, and it is necessary to subdivide each and every effect and understand it thoroughly. Although this chapter purports to explain the physical chemistry associated with the origin of carbonate rocks, this problem is far from being solved. Many new approaches will be required, such as studies of surface energies (SCHMALZ, 1963), before one truly begins to understand the physical and chemical changes accompanying recrystallization of unconsolidated metastable carbonate minerals to stable carbonate minerals in carbonate rocks. One fruitful avenue of approach would appear to be study of the effect of Mg/Ca ratios of solutions from which carbonate minerals precipitate. ERENBURG (1961) reported precipitation of protodolomite (GRAFand GOLDSMITH, 1956) below 100°C from CaClz and MgClz solutions. One might suspect that, given sufficient time, protodolomite would recrystallize to ordered dolomite.

PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES

153

CHILINGAR and BISSELL (1 963b) presented some physical-chemical evidence which suggests that possible high Mg/Ca ratio of Precambrian sea waters prevented the formation of hard protective and skeletal structures of organisms, or largely hindered their formation. This could explain the scarcity of calcareous skeletons of invertebrates in Precambrian formations. Another interesting avenue of approach is that dealing with the influence of time, concentration, and pH. SIEGEL (1961) demonstrated that protodolomite can be produced at 25 "C if Ca2+ and Mg2+ ions were temporarily tied up in activated charcoal and could only come in contact with c 0 s 2 - ions very slowly. In addition, he found that somehow the sulfate radical plays an important role in dolomite formation, although admittedly at present its importance is not understood. Possibly S O P complexes with Ca2+ to form a CaS04O complex,which increases the Mg/Ca ratio to the critical point at which dolomite forms. Certainly, it comes as no surprise to see the so& radical somehow involved in this reaction because of the abundance of S O P in evaporite sequences where dolomite is so common (cf. CHILINGAR, 1956a,b). CHILINGAR and BISSELL(1963a) discussed the formation of dolomite in sulphate-chloride solutions and presented adiagram showing the region of dolomite formation in saturated chloride and sulphate solutions. The purpose of this chapter is to emphasize that (1) the formation of carbonate rocks (i.e., lithification and recrystallization) is a chemical problem; and (2) the chemical composition of water in which carbonate sediments were deposited, and that of interstitial water, during lithification, cannot be overlooked in studying their origin and subsequent history. In addition, experimental data are presented that suggest a major role played by magnesium ions of sea water in controlling the form of carbonate minerals precipitated and their persistence. Finally, an attempt is made to demonstrate the importance of these data in interpreting the origin of carbonate rocks. Experimental procedures

Aragonite was prepared at 70°C by the procedure described previously by WRAY and DANIELS (1957). This technique consists of adding 20 ml of a 1.O M Ca(N03)~ solution to 200 ml of a 0.1 M N a ~ C 0 3solution in a 500-ml beaker. Each solution was preheated and mixed in a water bath at 70°C. The resulting precipitate was allowed to equilibrate for approximately 2 min, filtered, washed with distilled water at 70"C, dried, ground with a mortar and pestle to minus 0.062 mrn, and then identified by X-ray diffraction. A calibration curve for aragonite and calcite was prepared following the procedure of LOWENSTAM (1954) and is described in detail elsewhere (TAFTand HARBAUGH, 1964). All chemicals used in the preparation of test solutions were Reagent Grade

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W. H. TAFT

Baker-analyzed. Test solutions were added to a weighed quantity of aragonite precipitate in 50-ml and 250-ml beakers, mixed, covered with Parafilm, and stored in the laboratory at specific temperatures.

INFLUENCE OF CHEMISTRY AND TEMPERATURE ON RECRYSTALLIZATION RATES

Recrystallization of aragonite to calcite would appear possible by either solution of aragonite and reprecipitation as calcite or by solid-state recrystallization. Solution of aragonite and subsequent reprecipitation as calcite obliterates original texture, whereas textures may be preserved by solid-state recrystallization. In view of perfect texture preservation in many ancient limestones, one must conclude that in these instances, if the original sedimentary particles were metastable carbonates, solid-state recrystallization had taken place. All experiments, listed in this chapter which show evidence of recrystallization, involved solution and reprecipitation. Aragonite in distilled water Recrystallization rate of aragonite to calcite in contact with distilled water is directly affected by temperature of the solution (Table I). Recrystallization rate at 3 "C is very slow averaging about 0.1 %/day. With increasing temperature, recrystallization speeds up, until at 70°C only 3 days are needed to convert a sample of

100

eP,

80

0

m

g

n

236

60

.# C

8

I

\A \A 40

A\

70'

A

20

0

-

I

Fig.1. Recrystallization of aragonite to calcite in distilled water (D.W.) as a function of temperature. At 70°C recrystallizationwas complete within 3 days; whereas at 3 "C, and after 236 days, only 22 % of the aragonite recrystallized to calcite.

z

TABLE I ARAGONITE IN CONTACT WITH DISTILLED WATER AT VARIOUS TEMPERATURES SHOWING INCREASED RATE OF RECRYSTALLIZATION OF ARAGONITE TO CALCITE WITH TEMPERATURE RISE

Chemistry of solution

Volume (mi)

Weight of precipitate (g)

Temp. ( "C)

Duration of experiment (days)

B

Mineralogy

01

Aragonite (weight %)

Calcite (wei.pht %) ~~

11-H

11-F

43

distilled water

distilled water

distilled water

40

50

50

0.1074

0.1996

0.1998

r 0

~~

Experiment

2>

3*1

23*2

70' 1

+

0 77 236

99 91 77

0 18 36 49 64 75 86 100

99 95 85 74 58 43 27 trace

0 3

+

99

0

+

trace 9 23 trace 5 15 26 42 58 63 99

+

trace 100

4

* ga

8

g

2;

az cl

>

6

0

z

2;

TABLE111 ARAGONITE IN CONTACT WITH MAGNESIUM SOLUTIONS OF VARIOUS CONCENTRATIONS1

Experiment

Chemistry of solution

Volume (nil!

Weight of precipitate (g)

50

0.2011

Temp. ("C!

Duration OJ experiment (days)

~~

3

2 p.p.m. Mg

4

2 p.p.m. Mg

50

5

5 p.p.m. Mg

50

0.1921

0.2010

23'2

70+1

23*2

0 28 54 70 86

Mineralogy Aragonite (weight %)

99 I0 45 15

+

Calcite (weight %) 1 30 55

0

85 100

0 40 I0 90 110

99 t 65 30 10

1 35 I0 90

0 8 15 33 I0 86 100

99 99 99 99 99 99 99

0

+ . +

130

5 p.p.m. Mg

50

0.2000

IO-tl

0 4 19 29

99 80 30 0

11

5 p.p.m. Mg

40

0.2188

23*2

0 108 246

100 14 trace

100

1

1

1 1 1 I 1 1 20 I0 100

0 26 99 -I

10

10 p.p.m. Mg

40

0.331 1

23*2

0 108 246

100 74 0

0 26 100

55

26 p.p.m. Mg

40

0.1 140

23'2

0 3 13 24 141

91 90 91 90 87

9 10 9 10 13

+ + + +

.

115

49 p.p.m. Mg

40

0.1008

23+2

0 66 180 300 365

99 99 99 99 99 J-

trace trace trace trace trace

131

10 p.p.m. Mg

50

0.2003

23*2

0 121

99

trace

133

10 p.p.m. Mg

50

0.2004

70-t1

0 12 29

trace

55 99

99 99

trace trace

136

50 p.p.m. Mg

50

0.1998

70*1

0 38

I 42

250 p.p.m. Mg

50

0.1997

70*1

0 38

11-G

1,330 p.p.m. Mg

50

0.1Ooo

23'2

0 120 200 320

400 470 1

+ 99 + 45

+ + 99 + 99 + 64 63 64 61

64 64

trace

+

i

$3

trace trace 36 37 36 39 36 36

Mineralogy is presented in weight :L and appears to be dependent upon temperature and quantity of magnesium ions relative to weight of precipitate.

L

5

158

W. H. TAFT

essentially 100% aragonite to calcite (Fig. 1). Of particular interest is the curve at 23 "C (Fig. 1) (close to standard temperature), which suggests that aragonite in contact with distilled water would recrystallize to calcite in less than 6 months in the natural environment. Magnesium effect

Because of the metastable nature of aragonite (JAMIESON, 1953; MACDONALD, 1956), any condition that slows down or prevents solution of aragonite and its reprecipitation as calcite may be a controlling factor that enables solid-state recrystallization to be the dominant process. KITANO and HOOD(1961) described the influence of organic material on the polymorphic form of CaC03 precipitated. In addition, organic matter secreted by carbonate shell-secreting organisms prevents chemical reaction between interstitial water and calcium carbonate of the shell until chemical or biological activity removes this layer. Magnesium ions in contact with aragonite appear to be capable of preventing recrystallization to calcite for an indefinite period by the process of solution and reprecipitation. Temperature and concentration of magnesium ions relative to quantity of aragonite appear to be important factors (Table 11,111).The empirical weight ratio of aragonite to magnesium in solution was termed the critical concentration ratio (TAFTand HARBAUGH, 1964). This ratio (Table 111) is critical to long-term aragonite preservation at laboratory temperature (23*2 "C), but changes with increasing temperature. At 2312 "C, 50 ml of a 5 p.p.m. solution of magnesium in contact with 0.2010 g of aragonite prevents aragonite solution and reprecipitation as calcite (Fig.2). If the temperature is increased to 70 "C, TABLE 111 EFFECT OF MAGNESIUM ION CONCENTRATION ON

Experiment2

3 11 10 5 131 55 115

Critical concentration ratio3 2,011 1,394 827 804 400 109 51

RE CRYSTALLIZATION^ Recrystallized Yes

no

+ +

+

+

+ + +

Based on empirical results from Table 11; temperature 23 f 2°C. Taken from Table 11. Grams of precipitate (in contact with solution)/grams of magnesium in solution.

159

PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES

40

80

100

Tome (days1

Fig.2. Recrystallization of aragonite to calcite as a function of weight ratio of aragonite to magnesium ions available in the solution. This ratio in experiment 3 (Table 11) is 2,011 ;recrystallization is complete within 87 days. The same ratio for experiment 5 (Table 11) is equal to 804; no detectable recrystallization occurs within 100 days.

100

0

0

49.4 p.p.m.Mg2’(115)

0

1

0

26 pp.m.Mg2+(55)

L c

-

u

k

n

40-

20

-

0-

I

I

Fig.3. Lack of recrystallization to calcite of aragonite in contact with solutions having 49.4, 26 and 1,330 p.p.m. of Mgz+. Numbers in parentheses refer to experiment numbersfrom Table 11.

solutions containing 5 and 10 p.p.m. of magnesium are ineffective, but 50 p.p.m. of Mg at this temperature prevents recrystallization (Table 11). Sea water contains 1,330 p.p.m. of Mg2+ which is sufficient to prevent recrystallization (Fig.3). In some instances, the magnesium concentration in interstitial water of fine-grained modern carbonate sediments tends to increase during compaction. Therefore, as interstitial water is squeezed from these sediments, magnesium ions remain

160

W. H. TAFT

in sufficient quantity to prevent recrystallization. If magnesium ions are flushed before lithification, however, recrystallization by solution and reprecipitation appears possible.

Calcium effect Increasing the quantity of magnesium ions relative to the amount of aragonite tends to prevent recrystallization if the critical concentration ratio is 804 or less (Table IV). Calcium ions, on the other hand, react in just the opposite manner. If the concentration of calcium ions relative to quantity of aragonite is increased, the rate of aragonite recrystallization to calcite also increases (Table IV, Fig.4). In addition to calcium ion concentration, temperature, and pH of the solution affects the recrystallization rate (Table IV). At 3 "C, recrystallization is sluggish, but with less calcium at 70°C recrystallization is complete within three days (Table IV). In order to investigate the effect of pH on recrystallization rates, 10 ml of an ethanolamine buffer solution (pH= 10.4) was added to 30 ml of a 400 p.p.m. solution of calcium in contact with 0.2006 g of aragonite at 70°C. Based on previous experiments of aragonite in distilled water (Fig. I), and aragonite in contact with 400 p.p.m. of Ca2+(Fig.4) that recrystallized to calcite within 3 days, this mixture at adjusted pH should have recrystallized similarly. This, however, was not the case (Table IV). During the 20 days duration of this experiment, no recrystallization to calcite was detected. Although this relationship indicates that pH may play a role in affecting recrystallization, it would be unusual to find pH values this high (10.4) in the natural environment.

01.000 p.p.m. Ca2+ A2.500p.p.m. Ca2+ 400pp.m. Ca2+

C P,

L U

20 -

0

0

I

5

Ib

115

2b

; 5

do

i5

do

-

d5

20

Time (days)

Fig.4. Dependence of recrystallization rate of aragonite to calcite upon Ca2+ concentration. Recrystallization rate increases with increasing Ca2+ion concentration.

TABLE IV ARAGONITE IN CONTACT WITH SOLUTIONS CONTAINING VARIOUS CONCENTRATIONS OF CALCIUM IONS AND AT DIFFERENT TEMPERATURES

Experiment

Calcium

Chemistry of solution

400 p.p.m. Ca

Volume

Weight of precipitate

(mil

(gl

Temp. ("C)

0.2008

23*2

50

Mineralogy

(days)

Aragonite (weight %)

Calcite (weight %)

99 90 17 55 30 7 trace 99 80 70 60 25 5 99 80

trace 10 23 45 70 93 99 trace 20 30 40 75 95 trace 20

1 0 99 0

99 100 trace 100

0 22 32

40

Calcium

Calcium Calcium

Calcium

1,OOO p.p.m. Ca

2,500 p.p.m. Ca

400 p.p.m. Ca

1,OOO p.p.m. Ca 2,500 p.p.m. Ca 720 p.p.m. Ca

300 p.p.m. Ca solution adjusted to pH 10.4 with ethanolamine buffer

50

50

50

0.2008

0.1996

40

0.1998 0.2002 0.1940

40

0.2006

23'2

23'2

70*1 3*1

70*1

F

Duration of experiment

15

Calcium

zcl

44 46 0 10 13 15 21 24 0 6 9 12 13 0 1

0 9 81 115 237 0 2 6 14 20

cl

+ +

50

+

99 99 97 97 89 99 99 99 99 99

+ +

+ + + + +

+

50

trace trace 3 3 11 trace trace trace trace trace

zi?! 8

g 5

az

8

c, >

tiz

5

E

162

W. H. TAFT

Effect of other ions Potassium and sodium chlorides increase the recrystallization rate of aragonite to calcite (Table V). The recrystallization rate also increases with increasing concentration of chlorides (Fig.5). Strontium has a retarding effect (Table V), similar to that of magnesium, and prevents recrystallization. The quantity of strontium necessary to preserve aragonite (> 100 p.p.m.), however, exceeds that present in sea water (8 p.p.m.). During precipitation of aragonite, in one instance the writer obtained vaterite with a trace of aragonite and a trace of calcite. In order to test whether or not vaterite could possibly be preserved in marine sediments, vaterite was placed in contact with distilled water and solutions containing magnesium and calcium ions (Table VI). No attempt was made to construct a calibration curve for the three carbonate minerals aragonite, calcite, and vaterite. By comparing the relative intensities of the more intense reflections of these minerals, however, one can obtain a general idea concerning their relative abundance. The second most intense peak of vaterite (intensity= 75; d=3.29) correspondsvery closely to the third most intense peak of aragonite (intensity= 52; d=3.273); and, therefore, as vaterite recrystallizes to aragonite, this peak does not diminish as rapidly as it should. Nevertheless, from the results presented in Table VI, one can conclude that vaterite, if formed in the marine environment, would recrystallize and be preserved as aragonite. If vaterite comes into contact with distilled water, or water containing calcium ions alone, recrystallization to calcite will be rapid.

100

3,000 P.pm CI- AS KCI

\ -

8.0. 0 30.000 D.D.m.CI-AS NaCl

” k

40

20

0

b

10

2‘0

2‘5

Tlme(day5)

Fig.5. Dependence of recrystallizationrate of aragonite to calcite upon concentration of potassium and sodium chloride solutions. The recrystallizationrate increases with increasing concentration of chloride solutions.

PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES

N

N

0

2:

0

3 6

2:

W

?

W

N

-

0

2

2: Y

6 mul

G

E: 2

-

ti Im

0

N W

163

-

tl Im

I-

d

I

TABLE VI VATERITE IN CONTACT WITH

Experiment

Vaterite

150

DISTILLED WATER CONTAINING VARIOUS CONCENTRATIONS OF MAGNESIUM IONS AND CALCIUM IONS1

Chemistry of solution

Distilled water

WeiRht of precipitate

Volume (mu

(g)

Temp. ("C)

150

2.5

23+2

Duration of experiment (days)

Mineralogy, intensities Aragonite

Calcite

0 1 9

42 4 0

loo+ lOOt

8 32

78 59 0

8

78 0 78 65 22 0 0

Vateritc

420 p.p.rn. Ca

150

2.5

2312

0

4 0

Vaterite

30 p.p.m. Mg

I50

2.5

2312

0

4 5 29 71 72

8 8 7

4

8 10 8

Vaterite

60 p.p.rn. Mg

150

2.5

23*2

5

1 71 80 32 1 0 1 71

90 32 1 Vaterite

240 p.p.rn. Mg

150

2.5

23*2

0 1 71 I05

321

4 17 36 72 4 4 5 13 68

Aragonite Vaterite

9 8

12 9 8

9 9 8 8

+

78 67

40 66

0

78 72 70

60 0

3 X

1

1

Intensities are used as a measure of relative abundance of aragonite, calcite, and coincident peak vaterite-aragonite.

%1

PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES

165

SUMMARY OF PHYSICAL CHEMISTRY

Some of the reactions between aragonite and test solutions, described in this chapter, can be summarized as follows: ( I ) Addition of a common ion, calcium in this instance, increases the recrystallization rate of aragonite to calcite. (2) Recrystallization rate of aragonite to calcite is markedly affected by temperature. Increasing the temperature of test solutions speeds up the recrystallization rate, whereas lowering the temperature reduces the recrystallization rate of aragonite to calcite. (3) Addition of a high pH solution to a mixture of aragonite and calcium, that would normally recrystallize rapidly, retards recrystallization. This pH value (10.4), however, is much higher than that normally found in modern carbonate sediments. (4) If the weight ratio of aragonite to magnesium ions in solution is less than 804, recrystallization of aragonite to calcite by solution and reprecipitation does not take place. (5) Strontium ions are effective in preventing recrystallization of aragonite to calcite, but the Sr2+ concentration necessary is much greater than that which occurs in marine waters. (6) Potassium and sodium-chloride solutions increase the recrystallization rate of aragonite to calcite over that of aragonite in distilled water. CONCLUSIONS

Lack of detectible recrystallization of metastable carbonate minerals in unconsolidated modern carbonate sediments may be attributed to the high concentration of magnesium ions in interstitial waters. If magnesium-ion concentration persists, the preserved metastable carbonate particles should be cemented by aragonite. This cementation by aragonite will preserve original textures and prevent large-scale recrystallization by aragonite solution and reprecipitation as calcite. Solid-state recrystallization of aragonite to calcite should preserve original chemistry such as Sr2+/Ca2+,12C/13C, and 1 6 0 / 1 * 0 ratios. These ratios should be useful in interpreting ancient depositional environments. In the case of aragonite solution and calcite precipitation, however, the resulting chemical ratios can be significantly altered as a result of changes of ion ratios in the interstitial waters. Preservation of aragonite in carbonate sediments for long periods favors formation of dolomite. This is particularly true in those environments where brines are concentrated at the surface by evaporation, the Mg/Ca ratio increases as a result of calcium carbonate precipitation, and brines percolate through aragoniterich sediment.

166

W. H. TAFT

ACKNOWLEDGEMENTS

Financial support for this work was provided principally by National Science Foundation Grants G- 19772 and GP-2527. Assistance of Catheryn MacDonald who did much of the laboratory work is gratefully acknowledged.

REFERENCES

BATHURST, R. G. C., 1959. Diagenesis in Mississippian calcilutites and pseudobreccias. J. Sediment. Petrol., 29: 365-376. CAROZZI,A. V., 1961. Reef petrography in the Beaverhill Lake Formation, Upper Devonian, Swan Hills area, Alberta, Canada. J. Sediment. Petrol., 3 1 :497-5 13. G. V., 1956a. Solubility of calcite, dolomite, and magnesite and mixtures of these CHILINGAR, carbonates. Bull. Am. Assoc. Petrol. Geologists, 40:2770-2773. CHILINGAR, G. V., 1956b. Note on direct precipitation of dolomite out of sea water. Compass, 34: 29-34. CHILINGAR, G. V . and BISSELL, H. J., 1963a. Formation of dolomite in sulfate-chloride solutions. J. Sediment. Petrol., 33: 801-803. CHILINGAR, G. V. and BISSELL, H. J., 1963b. Note on possible reason for scarcity of calcareous skeletons of invertebrates in Precambrian formations. J. Paleontol., 37: 942-943. CLOUDJR., P. E., 1962. Environment of calcium carbonate deposition west of Andros Island, Bahamas. U.S.,Geol. Surv., Profess. Papers, 350: 1-1 38. DEBOO,P. B., 1961. A preliminary petrographic study of beach rock. Proc. Natl. Coastal Shallow Water Res. Conf:, Ist, 1961, pp.456458. DURHAM, J. W., 1950. 1940 E. W. Scripps Cruise to the Gulf of California. Part 2: Megascopic paleontology and marine stratigraphy. Geol. SOC.Am., Mem., 43: 216 pp. ERENBURG, B. G., 1961. Artificial mixed carbonates in the CaC03-MgC03 series. J. Struct. Chem. (U.S.S.R.) (Eng. Transl.), 2: 178-182. GRAF,D. L. and GOLDSMITH, J. R., 1956. Some hydrothermal syntheses of dolomite and protodolomite. J. Geol., 64: 173-186. HARBAUGH, J. W., 1960. Petrology of marine bank limestones of Lansing Group (Pennsylvanian), southeast Kansas. Geol. Surv. Kansas, Bull., 142: 189-234. ILLING, L. V., 1964. Penecontemporary dolomite in the Persian Gulf. Bull. Am. Assoc. Petrol. Geologists, 48: 532-533. JAMIESON, J. C., 1953. Phase equilibrium in the system calcite-aragonite. J. Chem. Phys., 21: 1385-1 390. KITANO, Y .and HOOD,W. H., 1961.Effect of organic material on the polymorphic forms ofCaCO3. Geol. SOC.Am., Spec. Papers, 72: 86-87. LOWENSTAM, H. A., 1954. Factors affecting the aragonite/calcite ratios in carbonate-secreting organisms. J. Geol., 62: 284-322. LUCIA,F. J., WEYL,P. K. and DEFFEYES, K. S., 1964. Dolomitization of Recent and Plio-Pleistocene sediments by marine evaporite waters on Bonaire, Netherlands Antilles. Bull. Am. Assoc. Petrol. Geologists, 48: 535-536. MACDONALD, G. J. F., 1956. Experimental determination of calcite-aragonit? equilibrium relations at elevated temperature and pressures. Am. Mineralogist, 91 : 744-736. MURRAY,R. C., 1960. Origin of porosity in carbonate rocks. J. Sediment. Petrol., 30: 59-84. RUSSELL,R. J., 1961. Origin of beach rock. Proc. Natl. Coastal Shallow Water Res. Con$, Ist, 1961, pp.454-456. SCHMALZ, R. F., 1963. Role of surface energy in carbonate precipitation. Geol. SOC.Am., Spec. Papers, 76: 144. SHINN,E. A. and GINSBURG, R. N., 1964. Formation of Recent dolomite in Florida and the Bahamas. Bull. Am. Assoc. Petrol. Geologists, 48: 547.

PHYSICAL CHEMISTRY OF FORMATION OF CARBONATES

167

SIEGEL, F. R., 1961. Factors influencing the precipitation of dolomitic carbonates. Geol. Surv. Kansas, Bull., 152: 127-158. F. G. and HOWER, J., 1961. Mineralogy and early diagenesis of carbonate sediments. STEHLI, J . Sediment. Petrol., 31: 358-371. J. W., 1964. Modern carbonate sediments of southern Florida, TAFT,W. H. and HARBAUGH, Bahamas, and Espiritu Santo Island, Baja California: a comparison of their mineralogy and chemistry. Stanford Univ.Publ., Univ. Ser., Geol. Sci.,8: 1-133. WRAY,J. L. and DANIELS,F., 1957. Precipitation of calcite and aragonite. J . Am. Chem. SOC.,79: 203 1-2034.

Chapter 4 CHEMISTRY OF DOLOMITE FORMATION K. JINGHWA HSU University of California, Riverside, Calif. (U.S.A.)

SUMMARY

Chemical experiments under atmospheric conditions so far have not yielded any unequivocal answers on the stability of dolomite. The possibility that nesquehonite or hydromagnesite might be the stable magnesium carbonate at 25 "C and 1 atm. in the system MgC03-COz-HzO has added further complications. Unless further experimentation proves the contrary, the possibility exists that the stability of dolomite in the system C~CO~-M~CO~-COZ-HZOat 25°C and'l atm. is related not only to temperature and pressure, but also to the partial pressure of

coz.

The geologic occurrence of magnesium-bearing carbonates in Recent sediments is somewhat puzzling. The common occurrence of dolomite in ancient carbonate rocks, however, indicates that dolomite, rather than a mineral pair, is the stable phase under the low temperature and pressure conditions of carbonate diagenesis. The possibility that the calcite-hydromagnesite pair might represent a stable assemblage at 25°C and 1 atm. and extremely low pcoZ in the system CaCO3MgCO,-COz-HzO has been suggested-by the theoretical considerations and by experimental data. This tentative conclusion is not ruled out by the field evidence. Experimental evidence on the solubility of dolomite is controversial. The composition of the ground waters in dolomites is such that the writer believes the highest reported values (Kdr 1O-l') are more nearly correct than the lower values. This interpretation is not accepted by those who question whether equilibrium has been established or even approximated between a ground water and the solid carbonate phases of its host rocks. The controversy on the solubility of dolomite will probably not be resolved until dolomite is synthesized under controlled atmospheric conditions. Inasmuch as the solubility of dolomite is not known, the question whether any natural water (such as normal marine sea water) is saturated with dolomite cannot be satisfactorily answered. Experimental results on the composition of solution at dolomite-calcite-solution equilibrium differ radically, and deductions from such results have led to controversies. Nevertheless, all experimental results as well as deductions on the basis of ground water composition studies suggest that the Kdz value is less than 1 at room temperatures and atmos-

170

K. J. HSU

pheric or near-surface pressures. Paradoxically, sea water with a magnesium/ calcium-concentration ratio of 5.3 is apparently not dolomitizing. The reason is not clear, although alternative explanatidns have been suggested.

INTRODUCTION

The origin of dolomite involves two different problems. First of all, the chemical condition must have been such that the mineral dolomite could be formed as a stable phase. Secondly, the geologic history of a region must have permitted the chemical condition for the formation of dolomite mineral to persist long enough for sufficient quantity of the mineral dolomite to be formed in order to constitute a dolomite rock, or “dolostone”. This chapter is only concerned with the chemical problem of dolomite formation. Chemical experimental results are required to define specifically the conditions (temperature, pressure, chemical potentials of the various components in solution, etc.) under which the dolomite mineral can be formed. Unfortunately, experimental studies pertaining to dolomite formation under room temperatures and atmospheric pressures have not been very successful. Those who attempted to determine the solubility by dissolving dolomite in aqueous solutions have given widely divergent results; the solubility product of dolomite at 25°C and 1 atm., for example, as determined by the various experiments, ranges from 10-17 to 10-20, or a difference of three orders of magnitude! Deductions on the basis of controversial experimental data led, at times, to conflicting opinion. Further confusion arose because the occurrence of dolomite is not always what might be predicted on the basis of experimentation. This chapter is a review of the present status of our knowledge of the chemistry of dolomite formation under the relatively low temperatures and pressures of sedimentary and diagenetic conditions. The theoretical discussions begin with a consideration of the conditions of equilibrium as given by GIBBS(1875-1878) in his collected works, which form a basis for further theoretical deductions. A review of experimental work follows next. Finally, the geologic evidence pertaining to the chemistry of dolomite formation is presented.

-

A THREE-FOLD PROBLEM

-

Three questions may be asked regarding the chemistry of formation of the mineral dolomite. (I) Whether the double salt dolomite rather than a pair of single salts, calcite-magnesite, calcite-nesquehonite, or calcite-hydromagnesite, is the stable phase under a given temperature and pressure condition?

171

CHEMISTRY OF DOLOMITE FORMATION

(2) Whether the mineral dolomite could be precipitated from a solution of a given composition under a given temperature and pressure condition? (3) Whether the mineral dolomite should replace the mineral calcite (or aragonite) when a solution of a given composition at a given temperature and pressure is in contact with a solid phase of calcium carbonate? These three questions should be answered separately. The often-repeated phrase in geologic literature “conditions favorable for the formation of dolomite” is not meaningful unless one specifies the mode of formation.

STABILITY OF DOLOMITE

Theoretical discussions of conditions of equilibrium

GIBBS(1875-1878, p.63) stated that the variation of energy of any homogeneous part of variable chemical composition of a given mass is: dE

=

TdS - pdV

+ pldml -k pzdmz + . . . + pndmn

(1)

Where E denotes the total energy of the homogeneous part; T=its absolute temperature; S=its entropy; p=its pressure; V=its volume; ml, mz, . . mn are the quantities of the various substances; and pi, pz, . . . pn denote the chemical potentials of the various substances or the differential coefficients of E taken with respect to ml, mz, . . . md. If, for example, the whole mass consists of three homogeneous parts each consisting of the same two components, the variation of the energy of the system is expressed by dE’ d E ’ dE“’, if one distinguishes the letters referring to the different parts by accents. GIBBS(1875-1878, p.64) stated that the general condition of equilibrium requires that:

.

+

dE‘

+

+ dE” + dE”’ b 0

(2)

or:

To satisfy equation 3, the necessary and sufficient conditions of equilibrium are: The chemical potentials are intensive quantities: they can be expressed in J/g, or J/mole. Gibbs used the chemical potentials in terms of J/g; consequently, molecular-weight terms are involved in many of his equations. The chemical potentials are expressed here in terms of J/mole.

1

172

K . J. HSU

If the whole mass consists of three homogeneous parts (the first part consists of a substance s1, the second part of s2, and the third part of a substance s3 which is composed of s1 and s2 combined in the ratio l / l ) , then conditions of equilibrium are (GIBBS,1875-1 878, p.67):

On considering the reaction: CaC03 (calcite)

+ MgC03 (magnesite)

CaMg(CO3)z (dolomite)

(A)

at relatively low temperatures and pressures, when dolomite ideally does not contain CaC03 and MgC03 as separately variable components, the conditions of equilibrium are as follows: T' = T'= T"

P'

= P" = P"'

Y'CaCO,

ip"MgC03

p"'CaMg(C03)2

where ~'caco3.,U"MgC03 and ,U"'CaMg(C03)2 are the chemical potentials of the CaC03 in calcite, MgC03 in magnesite, and CaMg(CO& in dolomite, respectively. If calcite and magnesite are to form dolomite spontaneously, under a given T and p:

+

> p"'CltMg(C03)2

(7) Inasmuch as chemical potentials of those solid phases are a function of temperature and pressure only, and are independent of other variables, the stability of dolomite in the system CaCOs-MgCO3 depends thus upon temperature and pressure only. A complication arises, however, because of the uncertainties regarding the stability of magnesite. Free-energy calculations suggested that magnesite rather than nesquehonite is the stable magnesium carbonate phase at a temperature of 25 "C and a pressure of 1 atm in the system MgC03-H20 (GARRELS et al., 1960). Evidence on the basis of synthesis experiments suggested the contrary. KAZAKOVet al. (1957) repeatedly synthesized nesquehonite or hydromagnesite at room temperatures (1 5-24 "C) and atmospheric pressures, but failed to obtain magnesite under such conditions. Hydrothermal experiments by SCHLOEMER (1 952) also suggested that nesquehonite is the stable phase at temperatures below 80°C, above which, depending upon the Y'CaCO3

p"MgC03

40001-

173

CHEMISTRY OF DOLOMITE FORMATION

A

350°

:250°

0

Brucite 0

M \

Moqnesite

..

I w

--

N e s q u e honite 500

1,000

1,500 2,000 2,500 PRES'URE (ATM)

3,000

3,500

4,000

Fig.1. Stability of magnesite. (Modified after SCHLOEMER, 1952.). Hydrothermal experiments by Schloemer suggested that nesquehonite is the stable phase containing MgCO3 at room temperatures and atmospheric pressures. The univariant curve defining the equilibrium MgCOq8) 3Hz0 = M ~ C O ~ . ~ H ZisOdetermined (~) by experimentally determining the hydration temperature of nesquehonite at various pressures. The possibility of errors introduced by sluggishness of the reaction at low temperatures cannot be ruled out. That nesquehonite is the stable magnesiumcarbonate phase at room temperatures and atmospheric pressures is also indicated by the syntheet al. (1960), sis experiments of KAZAKOV et al. (1957). Free-energy calculations by GARRELS however, suggested that magnesite rather than nesquehonite is the stable phase in the system MgC03-H20 at 25 "C and 1 atm. total pressure. Crosses indicate runs in which the stable solid phase is nesquehonite; triangles, magnesite; and spheres, brucite.

+

confining pressure effect, nesquehonite may dehydrate to form magnesite and water (Fig. 1). If nesquehonite, rather than magnesite, is the stable carbonate in the presence of water, the following reaction must be considered:

+

CaC03 (calcite) MgC03.3HzO (nesquehonite) 3Hz0 (dolomite)

+

CaMg(CO3)z (B)

The conditions of equilibrium are:

where

and , U H ~ O represent the chemical potentials of MgC03. 3Hz0 in nesquehonite and that of water, respectively. In such a case, the stability of dolomite at room temperatures would be not only a function of T and p, but also that of the chemical potential of the water. $'MgC03.3H20

174

K. J. HSU

A still further complication arises because hydromagnesite could be the stable magnesium carbonate phase of the system MgC03-COz-HzO at room temperatures and very low pco, (KAZAKOV et al., 1957; GARRELS et al., 1960). If so, the following reaction must be considered:

+

4CaC03 (calcite) M ~ ~ ( C O ~ ) ~ ( O H ) Z .(hydromagnesite) ~HZO C02 e 4CaMg(CO& (dolomite) 4H20

+

The condition of equilibrium at any given T and p , would then be: T = T' = T" = T"' p = p' = p" = P"' 4p'CaC03

+

p"Mgp(C03)3(OH)2.3H20

+

+ pC02*4p"'CaMg(C03)2 + ~ P H , o

(C)

(9)

where ~ " M ~ ~ ( C O ~ ) ~ ( O H ) Zand . ~ H pcoZ ~ O represent the chemical potential of M ~ ~ ( C O ~ ) Z ( O H )in~ .hydromagnesite ~HZ~ and that of the C02, respectively. The question whether calcite-hydromagnesite pair or dolomite represents a stable phase at room temperatures is related, therefore, not only to T and p , but also to the chemical potential of water and to the partial pressure of COZ. Deductions on the basis of solubility experiments

The chemical potential of a one-component pure substance, expressed in J/mole is equal to its molar Gibbs Free energy, F. The change of free energy of the reaction A can thus be expressed by AFA, which is:

AFA = F"'

- (F'

+ F")

(10)

where F', F", and F"' represent molar free energies of calcite, magnesite, and dolomite, respectively. Equations 7 and 10 show that AFA must be negative if dolomite is to be formed from calcite and magnesite spontaneously at any given T and p . The AFA is related to solubility constants through a consideration of the following equilibria of calcite, magnesite, and dolomite with their saturated solutions: CaC03 (calcite)

s Ca2+ + CO&

MgC03 (magnesite)

zMgz+ + cos2-

CaMg(CO3)z (dolomite)

Caz+

+ Mgz+ + 2C0s2-

(D) (E) (F)

The free energy of a solution, F, at any given T and p , is related to,the activity of the ions, a, in solution by the relation (LEWISand RANDALL,1923, p.291):

F = F" -l- R T l n a

(1 1)

where F" is the free energy of a solution at an arbitrarily chosen standard state.

175

CHEMISTRY OF DOLOMITE FORMATION

Inasmuch as the free energies of the solids are equal to the free energies of their saturated solutions (FCa2+C0:-, FMg2+co:-, Fca2+Mg2+(co:-)2) at any given T and p, then:

F'

=

FCa'+Co:-

=

F"ca2+

+ Poco:-

f R T In Kc

F" = FMg2+co,2- = F0Mg2+-/ F"c0:- $- R T In Km

F"' = Fca2+Mg2+(c0:-), = FoMg2++ F"Ca'+

+ 2F"co:-

(12) (13)

-/ RTln Kd (14)

where Foca2+,FoMg2+and F"CO:- represent the free energies of Ca2+, Mg2+, and ions of a solution at an arbitrarily chosen standard state, and K,, Km, and Kd represent the equilibrium activity products (or solubility constants) of calcite, magnesite, and dolomite, respectively, at any given T and p. Thus, on substituting equations 12, 13, and 14 into equation 10, one obtains the condition of stability of dolomite, i f C032-

AFA = RTln-

Kd
Inasmuch as solubility constants can be determined by solubility measurements, AFA at any given T and p can thus be calculated from such experimental data. HALLA(1935), GARRELS et al. (1960), and HALLAet al. (1962), proceeded from such a theoretical consideration to determine the stability of dolomite on the basis of solubility measurements. Unfortunately, as discussed later (p. 179), different workers experimenting at the same T and p conditions have obtained different values of Kd; none of the results are universally accepted because equilibrium has not been ascertained during any of the experiments. Calculations based upon such debatable results are thus subjected to the same degree of uncertainty as the experimental results themselves. Nevertheless, calculated AFA values based on those widely divergent results are all negative, ranging from about -0.5 to -4 kcal. for the reaction A at 25 "C and 1 atm. (HALLA,1935; GARRELS et al., HALLA et al., 1962). Halla used the maximum reported Kd value in his calculations, which is three orders of magnitude larger than the minimum reported value used by Garrels in his calculations. The available experimental evidence is thus favoring the idea that dolomite, rather than calcite-magnesite, is the stable phase at 25 "C and a pressure of 1 atm. The change in Gibbs free energy involved in reaction B at room temperatures (25-38°C) and 1 atm. have also been calculated from solubility data (HALLA, 1935, p.79). The results also indicated a negative free energy change for such a reaction under atmospheric conditions. The same criticism concerning the establishment of equilibrium, however, must be'applied, and the calculated results have thus been viewed with skepticism. The stability field of dolomite and of the calcite-hydromagnesite pair at 25"Cand 1 atm. has been tentatively defined by GARRELS et al. (1960, p.416, f i g 3

176

K. J. HSU

on the basis of their solubility studies and free energy calculations. Their postulate contains also an element of uncertainty because of the difficulty of ascertaining equilibrium during solubility measurements of magnesium-bearing carbonates. Deductions on the basis of synthesis experiments

Early claims of having succeeded in synthesizing dolomite under atmospheric conditions (e.g., RIVIZRE,1939) were not supported by positive identification of the dolomite phase. GRAFand GOLDSMITH (1956, p. 178) have synthesized, at temperatures less than 100"C and unknown pressures, a calcium-magnesium carbonate phase with a calcium content somewhat greater than that of dolomite. Such a carbonate, termed protodolomite, has a composition ranging from Ca55Mg45 to Ca,,Mg4, and was formed at a temperature as low as 25 "C. These workers failed, however, to obtain dolomite with an ordered arrangement of Ca and Mg ions under low temperatures, although such dolomite could be easily synthesized at higher temperatures of 200-500 "C. Graf and Goldsmith accepted Halla's'tentative conclusion that dolomite, rather than the pair calcite-magnesite, is the stable mineral at room temperatures. They explained their failures in synthesizing ordered dolomite in terms of the kinetics of dolomite formation; they believed that crystallization under the low-temperature experimental conditions could not attain the ordered Ca-Mg configuration in dolomite. Recently, OPPENHEIMER and MASTER(1963) synthesized dolomite at 2225°C and 1 atm. in an experimental aquarium. The carbonate phase was identified by X-ray diffraction method. Whether an ordered dolomite or protodolomite was synthesized was not mentioned in the published preliminary report. Except for this one reported success, the repeated failures to synthesize dolomite under atmospheric conditions are well known to students of the dolomite problem. Commonly a hydrous magnesium carbonate, nesquehonite or hydromagnesite, co-precipitates with a calcium carbonate phase under atmospheric temperatures and pressures (e.g., KAZAKOV et al., 1957). The interpretation of the experimental evidence is very difficult. One might postulate that calcite and nesquehonite, or calcite and hydromagnesite, but not dolomite, represent the stable assemblage under atmospheric conditions, and that the dolomite synthesized in the aquarium represents a metastable biochemical precipitate. Alternatively, one might conclude that the rate ofthe dolomite formation without catalysis is so slow under atmospheric conditions that the metastable mineral pair tend to be formed from supersaturated solutions; the organisms in the experimental aquarium assumed the role of the catalyst which promotes the formation of the stable dolomite phase. Deductions from j e l d occurrences

Recent dolomite has been repeatedly discovered during the last few years (e.g.,

177

CHEMISTRY OF DOLOMITE FORMATION

ALDERMAN and SKINNER, 1957; JONES,1961; WELLS,1962; DEFFEYES et al., 1964). The Recent dolomite of Australia is calcium-rich, having a constant composition of Ca56Mg44; it was considered a protodolomite because of its structural resemblance to those synthesized (SKINNER, 1960). The Recent dolomite of the Antilles, ranging in composition from Ca56Mg44 to Ca54Mg46 has an ordered structure (DEFFEYES et al., 1964). These discoveries have dispelled much of the doubt that dolomite can be a stable phase under room temperatures and atmospheric pressure. On the other hand, the assemblage aragonite-hydromagnesite has also been reported from the Recent or Pleistocene sediments (ALDERMAN and VON DER BORCH,1960; GRAFet al., 1961). Aragonite is not the stable calcium carbonate phase under atmospheric conditions (MACDONALD, 1956). Also the surficial deposits of aragonite and hydromagnesite of Australia are replaced by dolomite at a few inches below the surface (ALDERMAN and VON DER BORCH,1960). These facts suggest that the aragonite-hydromagnesite pair might represent metastable phases precipitated from supersaturated solutions at atmospheric temperatures and pressures. An alternative explanation that hydromagnesite is the stable phase under very low atmospheric pcoZ,however, cannot be ruled out. Dolomite rather than the single-salt mineral pairs is found in ancient sedimentary formations containing calcium and magnesium carbonates. This fact alone strongly indicates that the double carbonate is the stable phase under the low temperatures and pressures of carbonate diagenesis.

PRECIPITATION OF DOLOMITE

In the heterogeneous equilibrium dolomite-solution: CaMg(CO3)z (dolomite)

Ca2+

+ Mg2+ + 2CO$-

(F)

at equilibrium under any given T and p (GIBBS,1875-1878, p.426): /&a2+

+

PMg2+

+ 2pCO,2-

=

p”’CaMg(C03)2

(16)

where pca2+, p M g 2 + and pc0,2- represent the chemical potentials of calcium, magnesium, and carbonate ions in the solution phase. The additional condition that dolomite represents a stable phase is expressed by equation 7: P‘CaC03

+ P”MgC03 > p”’CaMg(CO.&

Today activity and related quantities rather than chemical potential serve as the usual medium for expressing the results of thermodynamic measurements on solu-

178

K. J. HSU

tions. Equation 16 is expressed in terms of activities in the better known form of mass-action lawl: (aca2+)(aMg2+)(aco:->2

(17)

= Kd

(aMg2+),and (ace:-) represent the activities of calcium, magnesium where (ma2+), and carbonate ions in the saturated solution, and Kd is the equilibrium activity product, or the solubility product, of dolomite and is a constant at any given T and p. Solubility experiments

Several attempts have been made to determine the solubility of dolomite under room temperatures and 1 atm (HALLA,1935; YANAT'EVA, 1950, 1955a, 1955b, 1956, 1957; KRAMER,1959; GARRELS et al., 1960; Von Tassel in HALLAet al., 1962). So far all solubility experiments consisted of dissolving dolomite in aque. ous solutions. Different analytical techniques in determining the composition of the solutions have been used: for example, GARRELS et al. (1960) determined the carbonate concentration indirectly by measuring the pH of the solutions. Commonly after an initial increase, the concentration of a solution dissolving dolomite became practically constant within the errors of measurements. Inasmuch as the solubility experiments cannot be continued forever, the final apparently constant concentration of the solution is assumed as the equilibrium concentration. The equilibrium constant Kd has been calculated from the relation: Kd = (mCa2+)(7Ca2+)

(mMg2+)(yMg2+)(mCO:-)2

(yCO:-)2

(18)

where (mca2+),(mMg2+)and (rnco:-) are the molar concentrations, and (yca2+), (yMg2+),and ( y ~ 0 , 2 -are ) the activity coefficients of the ions in solution, which are usually calculated through the use of the Debye-Hiickel relations for very dilute solutions (KLOTZ,1950, p.239). Inasmuch as attempts to precipitate dolomite under controlled atmospheric conditions have not been successful, the usual procedure of checking equilibrium by precipitating a solid phase from its supersaturated solution has not been underThe mass-action law expressed in terms of concentration of solute (in a very dilute solution) has been derived by GIBBS(1 875-1 878, p.424426) through the relation, which is approximately valid for very dilute solutions under ordinary pressures: p = function ( t ) RT In rn The term activity was introduced by Lewis and was defined by the equations (LEWISand RANDALL,1923): p = function ( t ) RT In a

+

p(+) =

+

1

On substituting activity terms for concentration terms in very dilute solutions, the mass-action (1936) gives a thorough discussion of the definitions law is expressed in terms of activity. ADAMS of activity.

179

CHEMISTRY OF DOLOMITE FORMATION

TABLE I COMPARISON OF EXPERIMENTALLY DETERMINED AND ESTIMATED VALUES OF DOLOMITE SOLUBILITY

Investigators

Kd

Values determined experimentaNy Von Tassel in HALLA et al. (1962)

KRAMER (1959) YANAT'EVA (1955a) GARRELS et al. (1960) Values estimated from composition of subsurface waters

HOLLAND et al. (1964) Hsu (1963) BARNES and BACK(1964)

taken in those experiments. All published data on the solubility of dolomite under atmospheric conditions, therefore, contain an uncertainty. This uncertainty left geochemists in doubt as to which of the widely divergent results obtained by different experimenters is more nearly correct. The value of Kd at any given temperature and pressure should be a constant. The reported values of & for 25 "C and 1 atm., calculated from solubility measurements, however, range from 10-17 to 10-20, a difference of three orders of magnitude (Table I). Two alternative explanations have been advanced to explain the discrepancy of Kd values calculated from laboratory experiments. One school of thought suggested that the highest reported values (Kd z 10-17) should more nearly approximate the equilibrium value than the lower values, because the equilibrium has always been approached from the undersaturation side (Hsu, 1963). Another school of thought suggested that the lowest reported values (Kd z 10-20) should represent the equilibrium value; higher values resulted from grinding of dolomite, which caused disordering of the surface of dolomite crystals, either during sample preparation or from the stirring or tumbling during the measurement itself (GARRELS et al., 1960, p.417). This controversy cannot be entirely resolved until dolomite can be synthesized under controlled atmospheric conditions. It can be pointed out, however, that the high estimates of dolomite solubility in ground water can not be explained in terms of disordering by grinding.

Synthesis experiments The composition of the solution phase in the dolomite-synthesis experiments of Graf and Goldsmith is unknown. The dolomite synthesized by Oppenheimer was

180

K. I. HSU

precipitated from a solution similar to sea water in composition; he reported (personal communication, 1964): “The solution was 1 1 of artificial sea water, composition of Lyman and Fleming (In: SVERDRUP et al., 1942, p.186), plus 0.1 g peptone, 0.01 g FeP04, 0.1 g KN03 and 50 ml of soil extract prepared from mangrove peat. To the liter of solution were added 50 g each of quartz and Mg-calcite (7%) with a particle size of approximately 100p and an inoculum consisting of a mixture of microorganisms from an algal mat from the shore line near The Marine Laboratory, Miami. Sterile controls were maintained by adding 0.5 % mercuric chloride to the above solutions without inoculum. The solutions were then subjected to 12 h of light and dark, at a temperature of approximately 20°C for 30 days. During alternate dark and light periods, the pH of the solution had a diurnal fluctuation between 7.6 and 9.2 and the carbonates were both dissolved and precipitated and quartz dissolved. After 1 month of diurnal pH fluctuation, X-ray analyses of the residual carbonate material showed the presence of dolomite.” The temperature of Oppenheimer’s synthesis experiments varied ‘between 22 O and 25 “C. Oppenheimer believed that the magnesian calcite was dissolved, and both calcite and dolomite precipitated during the pH change caused by the biologic activities of the living organisms. Inasmuch as the pH and the carbonateion concentration of the solution at the time when dolomite was precipitating are unknown, solubility constant K d cannot be obtained from the data of this experiment. One is left with the uncertainty whether K d is more nearly equal to 10-17 or to 10-20. ROSENBERG and HOLLAND (1 964) studied the stability relations of calcite, dolomite, and magnesite in 2 M chloride solutions at temperatures ranging from 275°C to 420°C and pressures of a few hundred atmospheres. They have been able to synthesize dolomite and to analyze the calcium and magnesium ion concentrations of the solution phase. Their data are, however, insufficient to permit a calculation of the & value. If one is so bold as ( I ) to assume that the activity coefficient ratio, ( Y M ~ ~ + ) / ( Y Cfor ~ ~such + ) , concentrated solutions is not much different from unity, and (2) to make an extrapolation from such high temperatures to room temperatures, then one could obtain, by using the relation which is expressed by equation 19, that K d at 25 “C is of the order of 10-17 (Fig.2). Such a long range extrapolate with a very uncertain assumption is, of course, extremely speculative. Composition of subsurface waters in dolomite

Studies of the chemical composition of the natural waters have served as an independent check of the validity of the various experimental data. Namely, the solubility of dolomite can be computed from the analysis of a subsurface water which

181

CHEMISTRY OF DOLOMITE FORMATION

3 4-

\

33-A\m

:::

3029-

\

2 8 2 7-

-

?\

26-

\

2 5 -

0-

24-

w

23-

-

22'

x

2 1 -

+

20-

1

\

\

\

\

\

19-

1817I 6 -

1514-

6

02

04

06

08

12

10

14

16

18

210

Fig.2. Variation of the calcium-magnesium concentration ratio of a solution at calcite-dolomiteand HOLLAND, solution equilibrium as a function of temperature. (Modified after ROSENBERG 1964.). Data at lower right corner are taken from the hydrothermal experiments of ROSENBERG and HOLLAND (1964)at high temperatures and some unspecified high pressures. Data at upper left corner are taken from a ground-water study by Hsu (1963). Oil-field brine data have not yet been systematically studied. The question mark on the diagram indicates the range of temperature and concentrations of oil-field brines possibly in equilibrium with both calcite and dolomite (CHAVE, 1960). Such an extrapolate from the high-temperature data at high pressures to low temperatures at a much lower pressure is very speculative. The relation of the concentration ratio to the activity ratio at equilibrium depends upon the activity coefficient ratio of the calcium and magnesium ions in solution. For the very dilute solutions studied by Hsw (1963), the concentration ratio is approximately the same as the activity ratio. Squares indicate the temperatureconcentration ranges in which the stable carbonate phase is dolomite, and triangles, calcite.

has equilibrated with dolomite. The difficulty of such an approach is two-fold: (1) sampling problems, and (2) difficulty of ascertaining equilibrium. A most serious sampling problem arises from the tendency of the bicarbonate ion in water samples to equilibrate with atmospheric COZ before an analysis could be made. Consequently, subsurface waters from carbonate terranes are often apparently supersaturated with respect to the carbonate phases when calculations involve pH and (mco,2-) terms (e.g., BACK,1960; HOLLANDet al., 1964). To circumvent the difficulty, one could utilize the relation that at any given T and p: Kd = (aMg2')/(aca2')

'

Kc2

(19)

where ( u M ~ ~and + ) (aca2+) represent the activities of magnesium and calcium ions of a solution in equilibrium with both calcite and dolomite. Using this method, Hsu (1963) obtained a figure of 2 * 10-17, and HOLLANDet al. (1964) obtained a

182

K. J. HSU

figure of the about same order of magnitude (IO-l7). Those results led to the belief (Hsu, 1963; BARNESand BACK,1964) that the experiments which yielded the highest published figures on the solubility of dolomite most likely have approximated equilibrium. The question whether ground waters in dolomites have equilibrated with the carbonate phases in the host rocks has not been resolved. Due to its slow flow rate a ground water might maintain a prolonged contact with its host rock under similar temperature and pressure conditions; the opportunity of achieving equilibrium in nature is thus far greater than that afforded by laboratory experiments of limited durations. That calcite-dolomite-solution equilibrium might actually be established during the flow of ground waters through dolomitic limestones is indicated by the relatively constant activity ratio of such waters (Fig.3). Such a constant ratio constitutes a necessary, but not sufficient, proof of equilibrium.

2.01

-

",-

DOLOMITE

A

. . :. , . ........ .

....

0.5-

.

STABLE

.

.

.

.

~

A

0.4-

A

.

0.3-

CALCITE 0.2-

A

A

STABLE

A

A

A

2

3

4

5

6

7

0

9

[caZ'] rnMal/l

Fig.3. Magnesium/calcium molar concentration ratio of shallow ground waters, and the postulated stability fields of calcite and of dolomite at about 25°C and at near-surface confining pressures of a few atmospheres. (After Hsu, 1963.). Data on the chemical composition of dolomitic limestones are taken from Hsu (1963). Data on the chemical composition of waters from limestones and from dolomites are taken from WHITE et al. (1963). Note that the limestone waters all have magnesium/calcium ratio equal to or less than the postulated ratio at dolomite-calcitesolution equilibrium, and that the dolomite waters all have magnesium/calcium ratio equal to or greater than the postulated equilibrium ratio.

CHEMISTRY OF DOLOMITE FORMATION

183

Composition of surface waters related to Recent dolomite precipitation

Solubility of dolomite could be estimated if a natural water which is precipitating dolomite could be analyzed. ALDERMAN and SKINNER (1957, p.566) believed that the Recent dolomite of Australia was precipitated from waters which are similar to sea water in composition, but which have a high pH of about 9.2 and a salinity half of that of an average sea water. No attempts were made to calculate the solubility constant of dolomite. JONES(1961, 1963) made a detailed study of the chemical composition of the surface waters in the Deep Spring Playa region, California, where Recent dolomite has been found. He reported that “dolomite ooze coats the bottoms of all surface inflow channels (to the Deep Spring Playa) from springs” implying that the precipitation of dolomite might be related to the evaporation of such spring waters. The spring waters contain very little dissolved solids and have a magnesium/calcium concentration ratio similar to that of the ground waters in dolomitic limestones (cf. HSU, 1963, and JONES,1963). This fact would support the postulate of for the value of K d . An uncertainty remains, however, because the composition of the evaporated spring water which deposited dolomite might have been significantly different from that of the fresh spring waters. REPLACEMENT OF CALCIUM CARBONATE BY DOLOMITE

On considering the heterogeneous equilibria: CaMg(C03)~ CaC03

Ca2+

+ Mg2+ + 2Coa2-

zCa2+ + C032-

the conditions of calcitedolomite-solution three-phase equilibrium are:

T = T’ = T’” p = p’ = p”’ PCa2+

pca2+

+ +

PMg2+

+ 2PC032-

= P”‘CaMg(C03)e

P C O , ~ - = P’CaCO3

Expressed in terms of ion activity, at equilibrium under any given T and p : (aca2+)(am2+)(ace:-)' (aca2+)(aco,2-) = KC

= Kd

At the three-phase equilibrium, therefore, the following relation would hold true: (aMg2+)/(aca2+) = Kd/Kc2

= Kdz

(22)

The magnesium/calcium activity ratio of a solution in equilibrium with both calcite and dolomite is a constant at any given temperature and pressure, and is

184

K. J. HSU

represented by the abbreviation Kdz. Dolomitization of a calcium carbonate could occur if the magnesium/calcium activity ratio of a solution in contact with a calcium carbonate would exceed the value of Kdz. On letting the ion activity terms be substituted by terms of ion concentrations, one gets: (mMg2+)

(yMg2+)/(mca2+)(yCa2+)= Kdz

(23)

Equation 23 can be written as: (mMg2+)/(mCa2+) = Kdz

*

(yCa2+)/(rMg2+)

(24)

The activity coefficients, YMg2+ and yca2+, are not only a function of T and p , but also a function of the concentrations of the various ions in solution. Thus, the ion-concentration ratio at dolomite-calcite-solution three-phase equilibrium is not necessarily a constant at any given T and p.

Solubility experiments Several experiments have been attempted by different investigators to obtain the magnesium and calcium ion concentrations of a solution in equilibrium with both calcite and dolomite at room temperatures and atmospheric pressure. Timeconcentration plots have indicated that to achieve calcite-dolomite-solution equilibrium is even more difficult than to obtain the simpler dolomite-solution twophase equilibrium (YANAT'EVA,1950, fig. 1). The results of different experiments do not agree. The wide discrepancies in reported values are clearly indicated in Table 11. The magnesium/calcium concentration ratio at the calcite-dolomite-solution three-phase equilibrium for the MgC03-CaC03-C02-H20 system should be a constant at a given temperature, pressure, and a constant partial pressure of C02. The reported values range from 0.017 (at 17 "C) to 0.146 and 0.352 (at 25 "C).Nene of the experimenters have demonstrated establishment of equilibrium through the TABLE I1 SOLUBILITY DATA OBTAINED BY DIFFERENT INVESTIGATORS

Experimenter

Temperature Composition at presumed equilibrium

Duration of experimenr

("C)

mca2+

in mll solution

mMgZ+'

mcaz+

(days)

BAR (1932) HALLA (1935)

17 25

YANAT'EVA (1950)

25

6.339 8.21 8.67 8.10

0.017 0.325 0.352 0.146

30 28 28 100

mMg2+

0.110 2.67 3.05 1.18

CHEMISTRY OF DOLOMITE FORMATION

185

precipitation of the solid phases from a supersaturated solution. One cannot be certain which, if any, of the reported values is more nearly correct. Solubility studies of the system C~CO~-M~CO~--COZ--HZOhave also been conducted at different temperatures (0-70°C) and partial pressures of COZ (0.0012-1 atm) by YANAT’EVA (1955a), who also evaluated the effect of addition of sulphate and chloride on the solubility relation of the system (YANAT’EVA, 1956; 1957). These results serve to renew the controversy of the effect ofpco, on the value of magnesium/calcium concentration ratio at calcite-dolomite-solution threephase equilibrium. BAR (1932) postulated that the ratio is a function of pco,. HALLA(1935) stated that the ratio is constant under any given temperature and pressure, and cannot be a function of any other factors such as pco,. Halla’s statement, however, was based upon an assumption that the ratio of the activity coefficients of calcium and magnesium ions in solution is unity; an assumption which is probably valid only for very dilute solutions. Yanat’eva’s results supported Bar’s postulate. Equilibrium, however, has not been ascertained during solubility measurements; and the reported results are controversial. Thus the question remains unsettled whether the magnesium/calcium concentration ratio of a solution at the three-phase equilibrium does decrease as a result of increasing ~ c o , . Deductions on the basis of subsurface waters The tendency for well-recognized mineral associations to recur in rocks of widely different age and locality is the single most important indirect evidence that approximate chemical equilibrium has been established in many metamorphic rocks. In a heterogeneous system of fluid-bearing rock, the solution in equilibrium with the solid phases of the enclosing rock should be characterized by an equilibrium composition. Thus, if ground water in a dolomitic limestone has equilibrated with the dolomite and calcite phases in a rock, the magnesium/calcium activity ratio of the fluid should be a constant under a given temperature and confining pressure (equation 22). A study of the chemical composition of ground waters in dolomitic limestone has been undertaken (Hsu, 1963). The values of the magnesium/calcium concentration ratio of such waters fall within a very narrow range with an average of about 0.8, even though the calcium or magnesium concentration varies from 1 to more than 10 mmoles/l (Fig.2). The activity ratio, (aMg2+)/(acaz+),should be approximately the same as the concentration ratio, because the magnesium/calcium activity coefficient ratio is approximately equal to unity for these waters which contain less than 1 part per thousand of dissolved salts. The relatively constant activity ratio suggests that calcite-dolomite-solution equilibrium might be approximated during the flow of ground waters through dolomitic limestone. The value of K d z at 25°C and a pressure of a few atmospheres is thus estimated to be about 0.8 (Hsu, 1963), which corresponds to a K d value of about 2 * 1O-l’.

186

K. J. HSU

This result is consistent with that extrapolated from the data of high-temperature experiments (Fig.2). Oil field brines of higher temperatures from deeply buried dolomitic limestones contain much dissolved salts. The Debye-Huckel relation can hardly be applied and Kdz for such waters cannot be ascertained. It is interesting to note, however, that such waters tend to have a magnesium/calcium concentration ratio of about 1/2 or 1/3 (e.g., CHAVE,1960, fig.5): such a ratio is what might have been postulated on the basis of very speculative extrapolate shown in Fig.2. Deductions on the basis of composition of sea water

A normal marine sea water contains 53.57 mg-atoms of Mg2+ and 10.24 mg-atoms of Ca2+/1 (SVERDRUP et al., 1942, p.173). It thus has a magnesium/calcium concentration ratio of about 5.3. If the ratio of the activity coefficient of these ions is unity, the magnesium/calcium ion activity ratio of sea water should also be 5.3, and thus considerably greater than the various values of Kdz reported by the various experimenters and by the students of ground water geochemistry. There is no geologic evidence, however, that dolomitization of Recent carbonate sediments by normal marine sea water is taking place anywhere. One could accept one of the following alternatives: ( I ) The sea water has magnesium/calcium activity ratio greater than K d z , but the kinetics of dolomite formation under room temperatures is so slow that dolomitization of lime sediments cannot take place, or (2) The sea water has a magnesium/calcium activity ratio smaller than K d z . Dolomitization of lime sediments by sea water under surface conditions is not possible until the chemical composition of the sea water is so modified by natural processes that its activity ratio becomes greater than the equilibrium ratio. Such an increased activity ratio might be related to an increase of the magnesium/ calcium concentration ratio, or to an increase of the magnesium/calcium activity coefficient ratio, or to both. No agreement can be reached at the present time. The numerous discoveries of Recent dolomite in places where the chemical composition of the sea water has been sufficiently altered seem to argue in favor of the second alternative. Still another possibility exists that hydromagnesite rather than dolomite is the stable phase containing MgC03 (in equilibrium with sea water) under the atmospheric partial pressures of C02. Such a hypothesis would postulate that the formation of dolomite under atmospheric temperatures and pressures is not possible unless P C O , of a solution is sufficiently different from that of the atmospheric pco,, so that dolomite becomes the stable phase containing MgC03. The discovery of Recent dolomites in high pH and presumably low pco, environment by ALDERMAN and SKINNER (1 957) seems to argue against such an idea.

187

CHEMISTRY OF DOLOMITE FORMATION

Deduction on the basis of synthesis experiments

As discussed on p. 176 magnesian calcite has been converted to calcite and dolomite in artificial sea water in an aquarium experiment by OPPENHEIMER and MASTER (1963). One might postulate that the presence of other substances, such as KNO3, soil extract, etc., sufficiently influenced the activity coefficients of the solution so that the magnesium/calcium activity ratio of the artificial sea water became greater than the K d z value at the given T and p. Or, alternatively, one might postulate that the activity ratio of some sea water is always greater than that at calcitedolomite-solution equilibrium; the living organisms served as a catalyst and promoted a reaction which has otherwise too slow a rate without a catalytic agent. Oppenheimer's experiment is interesting, but does not help resolve the question whether theoretically dolomite should form spontaneously in normal marine sea water at room temperatures and atmospheric pressures. ROSENBERGand HOLLAND(1 964) determined the magnesium/calcium concentration ratio of the solution at dolomite-calcite-solution equilibrium at high temperatures of 275-420 "C and pressure of a few hundred atmospheres. Their results show an exceedingly small magnesium/calcium concentration ratio at the three-phase equilibrium at such high temperatures (Fig.2,4). The solutions are too concentrated to permit a meaningful calculation of the activity ratio. An extrapolation of such results to room temperatures, however, is interesting because such a speculative extrapolate seems to confirm the deductions from other lines of evidence (Fig.2).

-2!!

450-

400-

Magnesite

2 350-

z

0

n

E 300 0 c 250

Dolomite

so Iu t io n

+

solution

-

Calcite 0.6

0.7

mCa2+ /(mCa2+

0.8

+ mMg*+

't

+ solution

0.9

1.0

) i n solution

+

Fig.4. The ratio in solutions in equilibrium with calcite, with calcite dolomite, and with magand HOLLAND, 1964.) nesite at temperatures between 275°C and 420°C. (After ROSENBERG Squares indicate runs in which dolomite was replaced by calcite; and triangles, calcite or magnesite replaced by dolomite. The presence of the vapor phase and the possible intervention of critical phenomena have been ignored. Circles indicate runs in which magnesite is stable.

188

K. J. HSU

CONCLUSION

Preceding discussions demonstrated clearly the unsatisfactory state of our knowledge on the chemistry of dolomite formation. One does not even know for certain that dolomite, rather than a mineral pair (calcite-magnesite, or calcite-nesquehonite), is the stable phase under room temperatures and atmospheric pressures. The published results of the solubility of dolomite at 25 "C and a pressure of 1 atm. differ by as much as three orders of magnitude. No two persons seem to agree on the value of magnesium/calcium activity ratio of a solution equilibrated with both calcite and dolomite. Under the circumstances of our present imperfect knowledge, postulates of the conditions that are favorable for the precipitation of dolomite, or for the replacement of calcite by dolomite have been speculative. Much has been written that the dolomite genesis is related to the pH, Eh, or pco, of the sedimentary or diagenetic environments. Preceding analysis of our present knowledge has furnished very little basis for such postulates. The carbonate ion activity of a solution is related to pH by the relation: (a ' ) ' H (aCO:-)/(a H2C03) = K H2CO3 (25) where KH,CO~ is a constant at any given temperature and pressure. An increase of carbonate ion activity resulting from an increased pH should favor the precipitation of a carbonate phase, but there is no theoretical basis and little experimental evidence to suppose that the rise of pH favors the precipitation of dolomite in place of calcite. Nor is there any apparent reason why dolomitization should be directly related to changes in pH of a solution; the conditions for replacement of calcite by dolomite at any T and p are determined by the magnesium/calcium ion activity ratio (equation 22) and apparently are unrelated to hydrogen ion activity. A theoretical possibility cannot be ruled out, however, that the formation of dolomite migth be related to changes in pH under certain circumstances, because the pH of a solution is related to the pco, of a solution, which in turn might have some influence on the relative stability of dolomite and hydromagnesite. The relation between'Ehand dolomite genesis is even more remote as neither the precipitation of dolomite nor dolomitization of lime sediments involves an oxidation-reduction process. The relation of the partial pressure of CO, of a system to the genesis of dolomite is controversial. The possibility that hydromagnesite might be the stable phase containing MgC03 in the CaC03-MgC03-C02-H20 system permits a working hypothesis that the precipitation of dolomite (in place of two single salts) might be related to pco,. It has been shown that K d z , or the equilibrium magnesium/calcium activity ratio, is not a function of pco,. Whether the equilibrium concentration ratio is related to pco, cannot be ascertained; there is no obvious reason for such a supposition unless the activity coefficient ratio ( ~ M ~ ~ + ) / ( Yisc ~ ~ + ) , significantly altered by variations in pco,.

a

The effect of T and p on dolomite genesis is also not very clear. An increase in temperature obviously increases the rate of dolomite formation. An influence of changing temperature on the stability relations of the dolomite in the system CaC03-MgC03-C02-H20 is shown in Fig.2, but this relation is not certain because of the present uncertainties on experimental results. An eventual understanding of the dolomite genesis is not completely unlikely, despite the existence of many controversies at the present moment. The discoveries of Recent dolomites permit field studies of the geochemistry of dolomite formation. Ground water studies and hydrothermal experiments provide some evidence to confirm the higher reported values of dolomite solubility at 25 "C and a pressure of 1 atm. The reported success of synthesizing dolomite under atmospheric conditions also points to the possibility that the equilibrium condition might eventually be ascertained during solubility measurements, and thus many of the present uncertainties might be resolved.

ADDENDUM

Recently LANGMUIR (1964), using the Garrels technique but giving the system more encouragement to reach equilibrium, obtained a solubility product 1.O * 10-17 for dolomite at 25°C and 1 atm. This work gave further credence to the view that the true value of the dolomite solubility product at 25°C and 1 atm. is not far from 2 10-17 as suggested by the works of many.

ACKNOWLEDGMENTS

The writer is indebted to Drs. Heinrich D. Holland of Princeton University, Princeton, N.J., Abraham Lerman of John Hopkins University, Baltimore, Md., and Frank Dickson of University of California at Riverside, Calif., who critically read and improved the manuscript. My late wife, Ruth, helped in many ways during the preparation of the manuscript.

REFERENCES

ADAMS,L. H., 1936. Activity and related thermodynamic quantities; their definition, and variation with temperature and pressure. Chenr. Rev., 19: 1-26. ALDERMAN, A. R. and SKINNER, H. C. W., 1957. Dolomite sedimentation in the southeast of South Australia. Am. . I Sci., . 255: 561-567. ALDERMAN, A. R. and VON DER BORCH, C. C., 1960. Occurrence of hydromagnesite in sediments of South Australia. Nature, 188: 931. BACK,W., 1960. Calcium carbonate saturation in ground water from routine analyses. U.S., Geol. Surv., Water Supply Papers, 1535-D, 14 pp.

190

K. J. HSU

BAR, O., 1932. Beitrag zum Thema Dolomitentstehung. Zentr. Mineral. Geol. Palaontol., Abt. A., 1932: 46-62. BARNES, I. and BACK,W., 1964. Dolomite solubility in ground water. U.S.,Geol. Surv., Profess. Papers, 475-D: 179-180. CHAVE,K. E., 1960. Evidence of history of sea water from chemistry of deeper subsurface waters of ancient basins. Am. Assoc. Petrol. Geologists, 44: 357-370. DEFFEYES, K. S., LUCIA,F. J. and WEYL,P. K., 1964. Dolomitization: observations on the Island of Bonaire, Netherlands Antilles. Science, 143: 678-679. GARRELS, R. M., THOMPSON, M. E. and SIEVER,R., 1960. Stability of some carbonates at 25°C and one atmosphere total pressure. Am. J. Sci., 258: 402481. GIBBS,J. W., 1875-1878. On the equilibrium of heterogeneous substances. The Scientific Papers of J. Willard Gibbs, 1. pp.55-349, 419425. Dover Publications, New York, N.Y., 1961. GRAF,D. L. and GOLDSMITH, J. R., 1956. Some hydrothermal syntheses of dolomite and protodolomite. J. Geol., 64: 173-186. GRAF,D. L., EARDLEY, A. J. and SHIMP,N. F., 1961. A preliminary report on magnesiancarbonate formation in glacial Lake Bonneville. J. Geol., 69: 219-223. HALLA,F., 1935. Eine Methode zur Bestimmung der h d e r u n g der freien Energie bei Reaktionen B (s) = AB (s) und ihre Anwendung auf das Dolomitproblem. Z. des Typus A (s) Physik. Chem. Leipzig., 175: 63-82. HALLA, F., CHILINGAR, G. V. and BISSELL, H. J., 1962. Thermodynamic studies ,on dolomite formation and their geologic implications: an interim report. Sedimentology, 1 : 296-303. HOLLAND, H. D., KIRSIPU, T. V., HUEBNER, J. S. and OXBOUGH, V. M., 1964. On some aspects of the chemical evolution of cave waters. J. Geol., 72: 36-67. Hsu, K. J., 1963. Solubility of dolomite and composition of Florida ground waters. J. Hydrol., I : 288-310. JONES, B. F., 1961. The hydrology and mineralogy of Deep Spring Lake, California. U.S.,Geol. Surv., Profess, Papers, 424-B: 199-202. JONES,B. F., 1963. The Hydrology and Mineralogy of Deep Spring Lake, Inyo County, California. Thesis, John Hopkins Univ., Baltimore, Md., 227 pp. M. M. and PLOTNIKOVA, V. I., 1957. The system of carbonate KAZAKOV, A. V., TIKHOMIROVA, equilibria (dolomite, magnesite). Tr. Inst. Geol. Nauk, Akad. Nauk S.S.S.R.,Geol. Ser., 64: 13-58. KLOTZ,M., 1950. Chemical Thermodynamics. Prentice-Hall, Englewood Cliffs, N.J., 369 pp. KRAMER, J. R., 1959. Correction of some earlier data on calcite and dolomite in sea water. J. Sediment. Petrol., 29: 465467. LANGMUIR, D., 1964. Thermodynamic properties of phases in the system Ca0-Mg0-COz-Hz0. Geol. SOC.Am., Progr. 1964 Ann. Meeting, 120 (abstract). LEWIS,G. N. and RANDALL, M., 1923. Thermodynamics and the Free Energy of Chemical Substances. McGraw-Hill, New York, N.Y., 653 pp. MACDONALD, G. J. F., 1956. Experimental determination of calcite-aragonite equilibrium relation at elevated temperatures and pressures. Am. Mineralogist, 41 : 744-756. OPPENHEIMER, C. H. and MASTER, I. M., 1963. Transition of silicate and carbonate crystal structure by photosynthesis and metabolism. Geol. SOC.Am., Progr. 1963 Ann. Meeting, 125A (abstract). RIVI$RE,A., 1939. Sur la dolomitisation des sediments calcaires. Compt. Rend., 209: 597599. ROSENBERG, P. E. and HOLLAND, H. D., 1964. Stability relations of calcite, dolomite, and magnesite between 275°C and 420°C in the presence of aqueous solutions of CaCh, MgClzand COZ. Science, 145: 700-701. SCHLOEMER, H., 1952. Hydrothermale Untersuchungen iiber das System Ca0-Mg0-COz-Hz0. Neues Jahrb. Mineral., Abhandl., 1952: 129-133. SKINNER, H. C. W., 1960. Formation of modern dolomitic sediments in south Australian lagoons. . Bull. Geol. SOC.Am., 71: 1976. Abstract. SVERDRUP, H. U., JOHNSON, M. W. and FLEMING, R. H., 1942. The Oceans. Prentice-Hall, New York, N.Y., 1089 pp. WELLS,A. J., 1962. Recent dolomite in the Persian Gulf. Nature, 194: 274-275.

+

CHEMISTRY OF DOLOMITE FORMATION

191

WHITE,D. E., HEM,J. D. and WARING, G. D., 1963. Chemical composition of subsurface waters. US.,Geol. Surv., Profess. Papers, 440-F: 67 pp. 0. K., 1950. The solubility of dolomite in aqueous salt soiutions. Zzv. Sektora YANAT’EVA, Fiz.Khim. Analiza, Znst. Obshch. Neorgan. Khim., Akad. Nauk S.S.S. R., 20: 252-268. YANAT’EVA, 0. K., 1954. Solubility of dolomite in water in the presence of carbon dioxide. Zzv. Akad. Nauk S.S.S.R.,Otd. Khim. Nauk, 6: 1119-1 120. YANAT’EVA, 0. K., 1955a. Solubility in the system CaC03-MgC03-HzO at different temperatures and pressures of COz. J. Gen. Chem. U.S.S.R. (English Transl.), 25: 217-234. YANAT’EVA, O.K., 1955b. Solubility isothermsat0” and 55’ in the system Ca, Mg//C03, so4-Hzo. Zzv. Sektora Fiz.Khim. Analiza, Znst. Obshch. Neorgan. Khim., Akad. Nauk S.S.S.R., 26: 266-269.

YANAT’EVA, 0. K., 1956. The nature of the solubility of dolomite in water and in calcium sulphate solutions at different partial pressures of C02. Zh. Neorgan. Khim., 1: 1473-1478. YANAT’EVA, 0. K., 1957. On the solubility polytherm of the system CaC03+MgS04 = CaS04 +MgC03-H20. Proc. Acad. Sci. U.S.S.R.(Chem. Sect., English Transl.), 1957: 155-157.

Chapter 5 STABLE ISOTOPE DISTRIBUTION I N CARBONATES EGON T. DEGENS

Division of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, Mass. (U.S.A.)

SUMMARY

A brief survey has been presented on the stable isotope geochemistry of carbonates. Emphasis was placed on sedimentary carbonates in view of the fact that most of the other chapters of this book are almost exclusively concerned with sediments. The principal goal of this chapter was to demonstrate in what way stable isotope studies may contribute to a better understanding of certain problems in the area of classical geology and petrography; the data were selected accordingly.

INTRODUCTION

The stable isotope geochemistry of carbonates has been thoroughly investigated for a number of reasons. In the first place, the common pure end-member carbonates (calcite, aragonite, and dolomite) are composed of only four light elements: (I) carbon, (2) oxygen, (3) magnesium, and ( 4 ) calcium, all of which contain at least two stable isotopes in sufficient relative abundance. In the second place, the methods of extracting carbon and oxygen from carbonates are relatively simple and straightforward, whereas isotope extraction techniques for other mineral groups are more time-consuming and cumbersome. Thirdly, carbonates are equally well at home in magmatic and metamorphic rocks (e.g., carbonatites, nepheline-syenites, marbles), hydrothermal ore deposits (e.g., siderite veins, accessory minerals), and in sediments (e.g., limestones, shell materials, dolomites). It is also noteworthy that carbonates can be a product of both inorganic and organic processes. Factors that determine isotope fractionation in nature have been extensively discussed by UREY(1947), CRAIG(1953, 1963), EPSTEINet al. (1953), EPSTEIN (1959), CLAYTON and EPSTEIN(1958), and others. Principally, most of the stable isotope fractionation in nature appears to be the result of exchange reactions occurring at or near equilibrium. Thus, knowledge of the isotope fractionation factors in natural systems may reveal detailed information on, for instance, paleotemperatures, mode of mineral formation, photosynthesis, and many other natural phenomena.

194

E. T. DEGENS

CARBON ISOTOPES

In nature, the distribution of the two stable carbon isotopes 12C and 13C (12C/13C terrestrial ratio is about 90/1) is predominantly determined by (I) kinetic effects, and (2) equilibrium processes. For instance, the enrichment in 12C in land plants over that of atmospheric COZby about 2 %can be partly attributed to the more frequent collision of 1zC160~with the photosynthesizing leaf, as compared to 13C160z. In general, carbon isotope data are reported as per mil deviation relative to the PDBI Chicago Belemnite Standard (CRAIG, 1953, 1957): R - 1) * 1,Ooo 613C = (Rstandard where R = 13C/12Cratio in the sample, and Rstandard = 13C/12Cratio in the standard. d l 8 0 is defined similarly in terms of l8O/16O ratio. The 'data for oxygen 6 values will differ by about 29.5 when reported as per mil deviation relative to Standard Mean Ocean Water (S.M.O.W.). The relationship between 6 1 8 0 ~ ~ ~ 1 and ~ ~ ~ O S . M .can O.W be. expressed as: = (POPDBI* 1.03) G1~0s.~.o.w.

+ 29.5

In the present chapter, all carbon isotope data are reported relative to PDBI, whereas the oxygen isotope data are reported relative to mean ocean water standard (the most commonly used oxygen isotope scale). Since publication of a detailed study on the distribution of stable carbon isotopes in nature by CRAIG(1953), many papers have appeared on this subject. With regard to carbonates, a few pertinent studies on 13C/12C ratios include WICKMAN (1952), LANDERGREN (1954), JEFFREY et al. (1955), CRAIG(1957), SILVERMAN and EPSTEIN (1939, VOGEL(1959), COMPSTON (1960), KREJCI-GRAF and WICKMAN (1960), DEGENS and EPSTEIN (1962,1964), ECKELMANN et al. (1962), and MUNNICH and VOGEL(1963). The distribution of carbon isotopes in the carbonate system is plotted in Fig.1. Carbonates exhibit a range of about 12% in 13C/12C ratio. The lightest carbonates are those associated with sulfur-evaporite domes (bacterial carbonates), and the heaviest ones occur in meteorites. In order to illustrate the pathway of stable isotope fractionation in the carbonate system, the precipitation and dissolution mechanisms of fresh-water and marine carbonates are briefly discussed here. It is well established that due to the low COz content (0.03% by volume) in the atmosphere (KEELING, 1958), only small amounts of C02 can be picked up by precipitates. Rain water, therefore, will merely yield carbonate concentrations up to about 1.2 mMol/l. Inasmuch as the usual content of dissolved carbonates in ground waters of humid regions falls in the range of 3-10 mMol/l, most of it

195

STABLE ISOTOPE DISTRIBUTION IN CARBONATES

averaae values

b-yI ~* carbonates marine carbonates hydrothermally altered limestone ot spring gases (COZ) atites (soevites and alvikites) fresh-water carbonates

---

well gases ( C o p )

L

-60

-40

”

-20

-15

-10

-5

8 ’3c

0

t5

t10

t50

t70

Fig.1. Distribution of carbon isotopes in carbonates and related materials. (Largely obtained 1951; UREYet al., 1951; CRAIG,1953; THODEet al., 1954; JEFFREYet al., from BAERTSCHI 1955; CLAYTON and DEGENS, 1959; VOGEL, 1959; COMPSTON, 1960; ZARTMAN et al., 1961; DEGENS and EPSTEIN, 1962, 1964; CLAYTON, 1963; KEITH and ANDERSON, 1963; G. D. Garlick, personal communication, 1964; TAYLOR et al., 1964; and others.)

has to come from sources other than atmospheric C02. As shown by VOGEL(1959) and MUNNICHand VOGEL(1963), the overwhelming portion of bicarbonate ions found in fresh waters is derived from biogenic sources in the soil. Namely, soil air, enriched in COz relative to the atmosphere by a factor of about 10-100, will equilibrate with percolating fresh waters and thus increase the carbonate content in the moving waters. Limestones in contact with these COz-enriched fresh waters will react in the following manner: CaC03

+ C02 + HzO s Cazf + 2HC03l-

This reaction actually involves a number of separate equilibria (WEYL, 1958), i.e., the dissociation of calcite into calcium and carbonate ions and the subsequent formation of the bicarbonate ions from the various carbonate species present in the aqueous and gaseous phases (c0s2-, HzC03, and CoZ(Hz0)). In equilibrium, the amount of calcium bicarbonate that can go into solution, therefore, depends on the partial pressure of COZ or the quantities of dissolved C02 in the system. Data’on the solubility product ofCqCO3 in saline waters are more difficult to obtain, inasmuch as-aside from temperature and hydrostatic pressure-the solubility product is a function of type and amount of the various solutes present. In addition, kinetics considerations are also very important. As shown by PYTKOWICZ (1964) and P. K. Weyl (personal communication, 1964), Mg ions in the

196

E. T. DEGENS

sea seem to interfere with the spontaneous nucleation of calcium carbonate upon supersaturation of sea water. The power dependence of the rate of nucleation increases from a second to a sixth order in the presence of magnesium. The inference is that CaC03 deposition in the oceans is largely a result of biogenic extraction. In summary, under normal fresh-water conditions, where the water is saturated with respect to CaC03 and the Mg content is negligible, dissolution and precipitation can only take place as the solubility changes due to changes in pressure, temperature, or chemical composition of the moving water. CaC03 deposition can be brought about, for instance, when fresh waters move into open spaces having a lower partial pressure of COZthan that which existed at the place of origin of bicarbonates. CaC03 deposition under marine conditions, however, appears to be largely governed by the activities of organisms that extract both calcite and aragonite during their life cycle. It is important to study the fractionation characteristics of the stable carbon isotopes that are established between the various molecular species of the natural carbonate cycle. In Fig.2, a model is presented that illustrates the fractionation

I

I I

I

I

I

t - t - -LEGEND LI

,

(therrnol decomposiflbn)

I I

(travertine)

t10

heovier

0 L

-10

-+lighter

I -20

blcorbonote corbonotes lond plonts

-30

Fig.2. 13C/12Cfractionation in the carbonate system under different environmental conditions. (After CRAIG,1953; MUNNICHand VOGEL,1962; and others.)

STABLE ISOTOPE DISTRIBUTION IN CARBONATES

197

steps of the 13C/W ratios. As mentioned before, soil COZ is predominantly derived from biogenic sources, e.g., respiration of plants, or decay of organic matter. According to CRAIG(1953) and others, the average land plant has a 613C of -25 as compared to -8 for atmospheric COz. Thus, biogenic COZin the soil is expected to be enriched in I2C by about 2 %. This is based on the findings of CRAIG(1954), WICKMAN ( 1 952), BAERTSCHI (1953), and others, that apparently no significant isotope fractionation is involved, at least during decay and respiration of common land plants. Direct studies on the carbon isotopic composition of soil air, however, are still lacking. Biogenic COZwhich is incorporated in the moving meteoric water is eventually instrumental in dissolving ancient carbonates which, in most instances, are of marine origin. The 13C/W ratio of the bicarbonate ion in the water is, therefore, determined by the isotopic composition of the biogenic COz and the marine limestone. Carbonates precipitated in a marine environment under equilibrium conditions are about 7-8%, heavier in I3C than atmospheric COz. The isotope relationship between COz(atm),dissolved carbonate ions, and marine limestones is presented in Fig.2. Assuming that the biogenic COz in the soil air has a 613C of -24, and the limestone source one of 0, the resulting bicarbonate will have a 613C of -12. Inasmuch as this bicarbonate may still stay in contact with biogenic COz, carbon isotope exchange will take place until equilibrium is attained. This will result in a lowering of the d13C value in the bicarbonate by as much as 5-6%, (Fig.2). In contact with atmospheric COz, on the other hand, equilibrium processes work in the opposite direction, i.e., fresh waters preferentially lose 12C. In the final stage, the bicarbonate in fresh waters exposed to the atmosphere will be isotopically similar to the dissolved carbonates in the sea. The speed of equilibration under various natural condition!; has been determined by 14C analysis. A review on this subject has been prepared by CRAIG(1963) and MUNNICH (1963). Fresh-water carbonates, therefore, may yield a wide range of 613C values from as low as about -20 to as high as $2 to +3. Most of the fresh-water carbonate deposits, however, fall in the range of approximately -5 to -15%, (BAERTSCHI, 1951; CLAYTON and DEGENS, 1959; KEITHand ANDERSON, 1963). Thermal decomposition of marine limestones will produce a COz having 613C identical to that of the carbonate precursor (Fig.2). In analogy to the marine and fresh-water carbon-dioxide system, the resulting bicarbonate will be enriched in 1% by about 7 % , and a carbonate forming from this source at room temperature will have a 613C of about +7-+8 %,. In summary, equilibrium processes predominantly govern the distribution of stable carbon isotopes in the natural carbonate system. Carbonates deposited in equilibrium with their surrounding water and gas phases should yield identical 613C values, independent of whether they are of organic or inorganic origin. It appears, however, that a great number of marine organisms secrete a carbonate

198

E. T. DEGENS

that is slightly enriched in 12C relative to the value predicted by theory for a system in isotopic equilibrium (CRAIG,1953; LOWENSTAM and EPSTEIN,1957; WILLIAMS and BARGHOORN, 1963). Inasmuch as Recent limestones from many areas also reflect this slight deviation in “X content from the expected equilibrium value, the previously proposed hypothesis that marine limestones are largely a product of life processes in the sea receives further support. Fresh-water carbonates, in general, are significantly different from marine carbonates. This is a result of 12C-enriched CO2 contributions to the continental carbon-dioxide system. Thus, isotope data may reveal information regarding the nature of ancient environments. Aquatic marine and fresh-water organisms thriving on the dissolved carbonates will indirectly affect the carbon isotope distribution of marine and lacustrine carbonates. During assimilation and respiration, the C02 content in the dissolved carbonate fraction will decrease or increase, respectively. The magnitude of organic activity and the available bicarbonate resources in the environment where the plants live will, therefore, determine the fluctuations in the 613C of the bicarbonate from water samples taken during daytime (assimilation) or nighttime (respiration). Diurnal and seasonal fluctuations in the isotope distribution of bicarbonate may account for some of the apparent “disequilibrium” 613C values recorded in marine carbonates. UREYet al. (1951) presented evidence for internal 613C variations as high as about 2x0 within the shell structure of a single belemnite. The carbon isotope distribution once fixed in the carbonates is apparently not significantly altered during diagenesis and metasomatism (CRAIG, 1953; DEGENSand EPSTEIN,1962, 1964). But it is noteworthy that the few Precambrian marine carbonates analyzed so far are often enriched by a few per mil in 12C relative to the average 613C of geologically younger limestones. In this context, carbon isotope data of organic materials reported by S. R. Silverman and W. R. Eckelmann (personal communication, 1964) are of interest. Based on hundreds of analyses, these two investigators showed that organic extracts of rocks older than about 400-500 million years are systematically enriched in l2C by a few per mil. The number of data on Precambrian carbonates, however, is too small to justify further elaboration on this subject. Little is known on the carbon isotope distribution in high-temperature carbonates. The 613C of marbles (CRAIG,1953) and hydrothermally altered limestones (ENGELet al., 1958) fall in the range of normal marine limestones. This adds further support to the contention that the 613C of sedimentary carbonates is not drastically affected during the post-depositional history. Carbonatites (BAERTSCHI, 1951; VON ECKERMANN et al., 1952; TAYLOR et al., 1964) and hydrothermal vein carbonates (G. D. Garlick, personal communication, 1964; TAYLOR et al., 1964), however, are enriched in 12C relative to normal marine carbonates. Inasmuch as the fractionation characteristids in the carbonate system are reason-

STABLE ISOTOPE DISTRIBUTION I N CARBONATES

199

ably well established, these isotope data may reveal important details on the isotopic composition of the primordial terrestrial carbon source and its subsequent history of fractionation. CLAYTON (1963) reported 613C values for carbonate minerals of two carbonaceous chondrites which are about 5-6 % greater than the ratio of any known terrestrial carbon. According to CLAYTON (1963), the isotopic differences observed may be a result of chemical isotope fractionation involving processes not common to earth, or it may be the result of incomplete homogenization of substances with different histories of nucleosynthesis. On the other hand, data by ABELSON and HOERING (1961) indicate that decarboxylation of amino acids-which are known to be present in meteorites-results in a significant l2C enrichment of the remaining amine by as much as 1-2%. Consequently, a COZ gas can be obtained which will be enriched in 13C by the same amount. So far, dolomites are only known from carbonaceous chondrites high in organic matter, and a cause and effect relationship between organic matter and carbonates may be anticipated.

OXYGEN ISOTOPES

UREY(1947), in his classical paper on the thermodynamic properties of isotopic substances, laid the foundation of modern isotope geochemistry. One of the first elements studied in detail during the early fifties for its isotope abundance in geological materials was oxygen (MCCREA,1950; UREYet al., 1951; BAERTSCHI and SILVERMAN, 1951;SILVERMAN, 1951;DANSGAARD, 1953; EPSTEIN and MAYEDA, 1953; EPSTEIN et al., 1953). In later work, in particular that by E P S T E I N (1959) ~~~~, and his associates (CLAYTON and EPSTEIN,1958, 1961; TAYLOR and EPSTEIN,1962), the principal laws that govern oxygen isotope fractionations in natural systems were outlined. Based on their findings and those of the earlier workers, a number of geological problems in the field of carbonate geochemistry can be solved. Oxygen has three stable isotopes: 160,170,and l80in a ratio of 99.759/0.0374/ 0.2039 for air oxygen. In dealing with natural variations of oxygen isotopes, the data are generally reported in terms of 1 8 0 / 1 6 0 ratios or P O , which is the per mil deviation in 1 8 0 / 1 6 0 ratio relative to Standard Mean Ocean Water (S.M.O.W.). Carbonates exhibit a range of about 4 % in 1 8 0 / 1 6 0 ratio, with carbonatites being the lightest and carbonates associated with certain continental evaporite deposits being the heaviest ones. A representative collection of data is included in Fig.3. The temperature dependence of oxygen isotopes present in the various molecular species of the C02-bicarbonate-carbonate-water system allowed paleotemperature determinations such as those by UREYet al. (1951), EPSTEIN et al. (1953), LOWENSTAM and EPSTEIN (1954,1956), EMILIANI (1955,1956, 1958), H. J. H. BOWEN(1960), COMPSTON (1960), and others. Their data indicate that it is possible

200

E. T. DEGENS

marine carbonates (syngenetic) marine carbonates (recrystallize

f re s h-water carbonates hydrothermally altered hydrothermal veins

-20 -10

-5

0

+5

+10

+15

+20

+30

+25

+35

8 1% Fig.3. Distribution of oxygen isotopes in carbonates and related materials. (Largely obtained 1951; DANSGAARD, 1953; EPSTEINand MAYEDA, 1953; LOWENSTAM’ and EPfrom BAERTSCHI, STEIN, 1954,1956,1957; CLAY TON^^^ EPSTEIN, 1958; EMILIANI, 1958; EN GEL^^ al., 1958; CLAYTON and EPSTEIN,1962, 1964; CLAYTON, 1963; G. D. and DEGENS,1959; UREYet al., 1961; DEGENS Garlick, personal communication, 1964; TAYLOR et al., 1964).

to use the 1*0/160 ratio of preserved marine carbonates for the determination of water temperature fluctuations in the ancient sea. The results of the comprehensive isotope study by EMILIANI (1 958) are of particular geological significance because they can be checked by different geological methods and observations. First of all, paleotemperatures inferred from the 180/le0 data of carbonates (“Globigerina ooze” facies) in Pleistocene deep-sea cores from the middle and equatorial Atlantic, the Caribbean, and the Mediterranean areas, show similar patterns. Furthermore, a generalized curve of temperature variations of tropical surface oceanic waters I

I

N o r t h America

Wisconsin(Proirie)

WurmP

Loufen

,&,Songomon lllinoion Wurm

I

Yormouih

Konson

Aftonion

Nebroskon

E u rope Riss/Wurm

Riss

MindeVRlss

Mindel

6

7

10

Gunz

Gunz/Mindel

c

0

L 30-1

2

3

4

5

8

9

11

12

13

14-stoqes

201

STABLE ISOTOPE DISTRIBUTION IN CARBONATES I

I

f r e s h water

I

J\,S 1 0 2

0 - CoCO3 *---I

12 6

,

?Ye

CoCO3

c----l

1

I

I

I

I

I

502

14 2

ZI

c

.-0 I 300.E 400 -

500

I

v

Fig.5. Variations in 180/160 ratio of carbonates and cherts with geologic age. (After DEGENS and EPSTEIN, 1962.)

W

t32

-

t30

-

c .-

5 +28 -

-0

0

z6 0 t 2 6 +24

-

8 "0

calcite

Fig.6. The W O relationship between coexisting dolomites and calcites of Recent age. marine environment; o = continental salt lake environment. (After EPSTEIN et al., 1964.)

+=

202

E. T. DEGENS

during the last 300,000 years correlates well with continental temperature variations inferred from loess profiles, pollen profiles, and with eustatic changes of sea level (Fig.4). Uncertainties in the reliability of paleotemperatures are introduced, however, as marine carbonates of older geologic periods are studied for their 1 8 0 / 1 6 0 ratios. In most instances, 6180 values of limestones and shell materials, unfortunately, do not indefinitely remain constant with geologic time; isotopic equilibration with the surrounding meteoric or connate waters, which is often stimulated by a general increase in temperature (geothermal gradient), makes the marine limestones or shell carbonates progressively lighter (increase in l 6 0 content). Thus, the original 1 8 0 / 1 6 0 record, as laid down during deposition, is diagenetically altered. The 6180 variation of a number of carbonates and coexisting cherts with geologic age is presented in F i g 5 There are, however, certain diagenetic environments known which apparently have preserved the original l 8 0 / 1 6 0 record even of late Paleozoic carbonates. This can be inferred either from the presence of internal isotope variations, the occurrence of metastable aragonite, or the perfect structural preservation of the calcite material (STEHLI,1956; COMPSTON, 1960; H. A. Lowenstam and S . Epstein, personal communication, 1964). Stable isotope investigations have also proven to be rather significant in studies concerning the origin of sedimentary dolomites. The isotope data of high-temperature mineral phases reported by CLAYTONand EPSTEIN(1958), ENGELet al. (1958), and EPSTEINet al. (1964) suggest that dolomites, which precipitated in an aqueous environment at room temperature, should be heavier by about &lo%, in 6180 over cogenetic calcite or aragonite. In view of the considerable isotope fractionation between calcite and dolomite, it might, therefore, be expected that sedimentary dolomites and calcites which precipitated under the same environmental conditions should be different in 6180 values by about 6-10 Isotope data of recent dolomite-calcite pairs from various localities, however, show no significant difference between calcite and dolomite (DEGENSand EPSTEIN,1964; EPSTEIN et al., 1964). The lack of such a relationship in the investigated sedimentary dolomite-calcite pairs and the consistent A-dolomite-calcite values1 of about zero suggest that the dolomite did not precipitate from an aqueous solution (Fig.6). Dolomite, even in recent samples, must have been derived by way of metasomatism of calcite, and dolomitization must have proceeded without significantly altering the 1 8 0 / 1 6 0 record of the precursor carbonate. Namely, the transformation of the original calcareous ooze must have taken place without chemically affecting the CO32- unit. Consequently, it can be inferred that the growth of dolomite did take place under solid state conditions from crystalline calcium carbonate.

x0.

1 A-dolomitexalcite is the difference between P O of dolomite and 6 1 8 0 of calcite, and thus is a measure of the magnitude of oxygen isotope fractionation between these two carbonate species.

203

STABLE ISOTOPE DISTRIBUTION IN CARBONATES

The same characteristics also hold true in the case of late diageneticepigenetic dolomitization, which does not introduce a major isotope fractionation between coexisting dolomites and calcites. Namely, the isotope ratio of the calcite precursor is inherited by the dolomite without any changes. Thus, isotope data suggest that all sedimentary dolomites, independent of age, environment, and mode of formation (syngenetic, diagenetic, or epigenetic), are products of calcite metasomatism. Aragonites, however, first have to become inverted to calcite, before dolomitization may proceed. In contrast to calcite and aragonite, dolomite does not easily adjust isotopically to changes in temperature, and l80/16O ratio of formation waters (EPSTEIN et al., 1964). This makes penecontemporaneous dolomites of marine origin a potential tool for the evaluation of paleotemperatures in the ancient sea. The d l 8 0 and d13C relationships that are established between coexisting dolomites and calcites of various origins are presented in Fig.7 and 8. The data illustrated in Fig.7 indicate that dolomites are either about equal or heavier in cY80relative

OC

.='/

/

0

marine pairs

-201

early diagenetic (penecontemporaneous A late diagenetic-epigenetic

/ /+ /

te r r est r ia I pairs

recent and ancient early dlagenl

hydrothermal pairs naturally occuring deposits + bomb experiments

-3OV

-30

I

-25

I

-20

I

-15

I

-10

8 I8O calcite

I

-5

0

t5

Fig.7. The 6180 relationship between coexisting dolomites and calcites. Black line: A-dolomitecalcite equals zero; dashed line: the dolomite-calcite relationship obtained by CLAYTON and 1958 (the assumed equilibrium curve between dolomite and calcite and a large reservoir EPSTEIN, 1958; DEGENS and EPSTEIN, 1964: and of hydrothermal fluids). (After CLAYTON and EPSTEIN, EPSTEIN et al., 1964.)

204

E. T. DEGENS

0

recent, early diagenetic ancient, early diagenetic + late diagenetic-epigenetic

terrestrial pairs recent, early diagenetic ancient, early diagenetic

-4

-%

-4

I -3

-2

-1

0

+I

' t3 +4 t6

+2

t5

813c calcite Fig.8. The 613Crelationshipbetween coexistingdolomites and calcites.Diagonal line: Sdolomiteand EPSTEIN, 1964.) calcite equals zero. (After DEGENS

to their coexisting calcites. That the majority of the calcites tend to approach the assumed equilibrium curve constructed by CLAYTON and EPSTEIN(1958) can probably be linked to the faster equilibration rate of calcite when compared to that of dolomite. Studies on high-temperature carbonates include those of BAERTSCHI ( 195l), CLAYTON and EPSTEIN (1958), ENGEL et al. (1958), CLAYTON (1961), G. D. Garlick (personal communication, 1964), O'NEILL and CLAYTON (1964), and TAYLOR et al. (1964). Most crucial for any future work in the area of high-temperature carbonate geochemistry appears to be the knowledge of the equilibrium constants for the various carbonate-water systems. CLAYTON (1 96 I), for instance, has experimentally determined the equilibrium constants for CaC03(,)-H20(1) at elevated temperet al. (1953), atures. By including data of the paleotemperature scale of EPSTEIN an equilibrium curve over a temperature range of about 1,000"C can be constructed. In Fig.9, In K is plotted versus the reciprocal of the square of the absolute temperature. An empirical equation which fits the experimental data over the 0"-750" C range is as follows: In K

=

2,730 T-2 - 0.000256

In case the equilibrium constants in two or more cogenetic mineral systems

205

STABLE lSOTOPE DISTRIBUTION IN CARBONATES

temperature ("C)

0

2

1

4

I 8

I 6

I I0

12

lo6/ T 2 Fig.9. Experimental equilibrium constants for CaC03(,,-H~0(~,. (After EPSTEIN et al., 1953; and CLAYTON, 1961.)

are sufficiently different, the 6 1 8 0 values of mineral pairs may allow, for instance, the evaluation of the temperature of mineral formation and the determination of the isotopic composition of the participating water phase. The usefulness of this type of approach has been shown, for instance, by CLAYTON and EPSTEIN (1958), ENGELet al. (1958), TAYLOR and EPSTEIN (1962), O'NEILL and CLAYTON (1964), and others. Geologically potential mineral pairs include: ( I ) calciteapatite, (2) siderite-magnetite, (3) calcite-dolomite, and (4) calcite-quartz. In case carbonate-containing magmatic and metamorphic rocks are studied (e.g., carbonatitesj, the various silicates coexisting with the carbonate can be used as proper mineral partners (TAYLOR et al., 1964).

CALCIUM A N D MAGNESIUM ISOTOPES

Stable isotopes of calcium differ in mass by up to 20% (40Ca versus 48Ca). Inasmuch as this is the largest relative mass difference of all the elements except hydrogen, a priori, studies on calcium isotopes appear promising. Mass-spectrometrical studies by HIRTand EPSTEIN (1964), however, indicate that there is a lack of large calcium isotope variations in nature in contrast to

.

206

E. T. DEGENS

oxygen, carbon, nitrogen, and sulfur. Namely, samples of different origins, i.e., meteorites, crystalline rocks, limestones, shell materials, ocean waters, bones and teeth, have about the same calcium isotope distribution. This may mean that elements in natural products which are bonded by ionic bonds show small isotopic variations when compared to those light elements that are bonded by covalent bonds. In the light of these results, a re-examination of magnesium isotopes would be relevant, because DAUGHTRY et al. (1962) reported 5 % variation in the 24Mg/26Mg ratios in dolomites. Similarly, the isotope data of CORLESS (1963) and CORLESS et al. (1963) have to be re-evaluated in view of the results by HIRTand EPSTEIN (1964). REFERENCES

ABELSON, P. H. and HOERING, T. C., 1961. Carbon isotope fractionation in formation of amino acids by photosynthetic organisms. Proc. Natl. Acad. Sci. U.S.A., 47: 623-632. BAERTSCHI, P., 1951. Relative abundances of oxygen and carbon isotopes in carbonate rocks. Nature, 168: 288-289. BAERTSCHI, P., 1953. Die Fraktionierung der natiirlichen Kohlenstoff-isotopen im Kohlendioxydstoffwechsel griiner Pflanzen. Helv. Chim. Acta, 36: 773-781. S.R.,1951. The determination of relative abundances of the BAERTSCHI, P. and SILVERMAN, oxygen isotopes in silicate rocks. Geochim. Cosmochim. Acta, 1: 3 17-328. BOWEN,H. J. H., 1960. Biological functionation of isotopes. Intern. J . Appl. Radiation Isotopes, 7: 261-272. BOWEN,R.,1963. Oxygen isotope paleotemperature measurements on Mesozoic Belemnoidae and G. D. HOBSON and their importance in paleoclimatic studies. In: U. COLOMBO (Editors), Advances in Organic Geochemistry. Pergamon, London, pp.271-283. R.N., 196l.Oxygen-isotope fractionation between 180/1e0 ratios in calcium carbonate CLAYTON, and water. J. Chem. Phys., 34: 724726. R. N., 1963. Carbon isotope abundance in meteoritic carbonates. Science, 140: 192-193. CLAYTON, R. N. and DEGENS,E. T., 1959. Use of carbon-isotope analyses for differentiating CLAYTON, fresh-water and marine sediments. Bull. Am. Assoc. Petrol. Geologists, 43: 890-897. R. N. and EPSTEIN,S., 1958. The relationship between laO/lBOratios in coexisting CLAYTON, quartz, carbonate and iron oxides from various geologic deposits. J. Geol., 66: 352-373. R.N. and EPSTEIN,S., 1961. The use of oxygen isotopes in high temperature geological CLAYTON, thermometry. J. Geol., 69: 447452. COMPSTON, W., 1960. The carbon isotopic compositions of certain marine invertebrates and coals from the Australian Permian. Geochim. Cosmochim. Acta, 18: 1-22. J. T., 1963. Variations of the Ratio 48Ca/(totalCa) in the Natural Environment. Thesis CORLESS, Mass. Inst. Techn. (unpublished). J. T., RHAN,K. A. and WINCHESTER, J. W., 1963. Variations in the ratio 48Ca/(total Ca) CORLESS, in natural materials. Trans. Am. Geophys. Union, 44: 69-70. CRAIG,H., 1953. The geochemistry of stable carbon isotopes. Geochim. Cosmochim. Acta, 3: 53-92. CRAIG,H., 1954. Geochemical implications of the isotopic composition of carbon in ancient rocks. Geochim. Cosmochim. Acta, 6: 186196. CRAIG, H., 1957. Isotopic standards for carbon and oxygen and correction factors for mass spectrometric analyses of carbon dioxide. Geochim. Cosmochim. Acts, 12: 133-149. CRAIG,H., 1963. The natural distribution of radiocarbon. Mixing rates in the sea and residence and E. D. GOLDBERG (Editors), Earth Science and times of carbon and water. In: T. GEISS Meteoritics. North-Holland, Amsterdam, pp. 103-1 14.

STABLE ISOTOPE DISTRIBUTION IN CARBONATES

207

DANSGAARD, W., 1953. The abundance of l*O in atmospheric water and water vapor. Tellus, 5 : 461476. DAUGHTRY, A. C., PERRY,D. and WILLIAMS, M., 1962. Magnesium isotope distribution in dolomite. Geochim. Cosmochirn. Acta, 26: 857-866. DEGENS, E. T. and EPSTEIN, S., 1962. Relationship between lsO/lsO ratios in coexisting carbonates, cherts and diatomites. Bull. Am. Assoc. Petrol. Geologists, 46: 534-542. DEGENS, E. T. and EPSTEIN,S., 1964. Oxygen and carbon isotope ratios in coexisting calcites and dolomites from Recent and ancient sediments. Geochim. Cosmochim. Acta, 28: 2344. ECKELMANN, W. R., BROECKER, W. S.,WHITUX~K, D. W. and ALLSUP, J. R., 1962. Implications of carbon isotopic composition of total organic carbon of some recent sediments and ancient oils. Bull. Am. Assoc. Petrol. Geologists, 46: 699-704. EMILIANIC., 1955. Pleistocene temperatures. J. Geol., 63: 538-578. EMILIANI,C., 1956. Oligocene and Miocene temperatures of the equatorial and subtropical Atlantic Ocean. J. Geol., 64: 281-288. EMILIANI, C., 1958. Paleotemperature analysis of core 280 and Pleistocene correlations. J. Geol., 66: 264-215. ENGEL,A. E. J., CLAYTON,R. N. and EPSTEINS., 1958. Variations in isotopic composition of oxygen and carbon in Leadville limestone and its hydrothermal and metamorphic phases. J. Geol., 66: 374-393. EPSTEIN,S., 1957. Nuclear processes in geologic settings. Natl. Acad. Sci.-Natl. Res. Council, Publ., 400: 20 pp. EPSTEM,S., 1959. The variations of the 1sO/160ratio in nature and some geologic implications. In: P. H. ABELSON(Editor), Researches in Geochemistry. Wiley, New York, N.Y., pp.217-240. T., 1953. Variations of l 8 0 content of waters from natural sources. EPSTEIN,S. and MAYEDA, Geochim. Cosmochim. Acta, 4: 21 3-224. EPSTEIN,S. BUCHSBAUM, R., LOWENSTAM, H. A. and UREY,H. C., 1953. Revised carbonatewater isotopic temperature scale. Bull. Geol. SOC.Am., 64: 1315-1 326. EPSTEIN, S., GRAF,D. L. and DEGENS,E. T., 1964. Oxygen isotope studies on the origin of dolomites. In: H. CRAIG,S. L. MILLERand G. J. WASSERBURG (Editors), Isotopic and Cosmic Chemistry. North-Holland, Amsterdam, pp. 169-180. HIRT,B. and EPSTEIN,S., 1964. A search for isotopic variations in some terrestrial and meteoritic calcium (in press). D. and DELAETER, J., 1955. On the l3C abundance JEFFREY, P. M., COMPSTON, W., GREENHALGH, of limestones and coals. Geochim. Cosmochim. Acta, 7: 255-286. KEELING,C. D., 1958. The concentration and isotopic abundances of atmospheric carbon dioxide in rural areas. Geochim. Cosmochim. Acta, 13: 322-334. KEITH,M. L. and ANDERSON, G. M., 1963. Radiocarbon dating: fictitious results with mollusk shells. Science, 141: 634-637. KREJCI-GRAF,K. and WICKMAN, F. E., 1960. Ein geochemisches Profil durch den Lias alpha (Zur Frage der Entstehung des Erdols). Geochim. Cosmochim. Acta, 18: 259-272. LANDERGREN, S., 1954. On the relative abundance of the stable carbon isotopes in marine sediments. Deep-sea Res., 1: 98-120. LOWENSTAM, H. A. and EPSTEIN, A., 1954. Paleotemperatures of the post-Aptian Cretaceous as determined by the oxygen isotope method. J. Geol., 62: 207-248. LOWENSTAM, H. A. and EPSTEIN,S., 1956. Cretaceous paleotemperatures as determined by the oxygen isotope method, their relations to and the nature of rudistid reefs. Intern. Geol. Congr., 20th, Mexico, 1956, Rept., pp.65-76. LOWENSTAM, H. A. and EPSTEM,S., 1957. On the origin of sedimentary aragonite needles of the Great Bahama Banks. J. Geol., 65: 364-375. MCCREA,J. M., 1950. On the isotopic chemistry of carbonates and the paleotemperature scale. J. Chem. Phys., 18: 849-857. M ~ ~ w c HK. , O., 1963. Der Kreislauf des Radiokohlenstoffs in der Natur. Naturwissenschaften, 50: 211-218. M ~ I C HK., 0.and VOGEL,J. C., 1963. Untersuchungen an pluvialen Wassern der Ost-Sahara. Geol. Rundschau, 52: 61 1424.

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O’NEILL,J. R. and CLAYTON, R. N., 1964. Oxygen isotope geothermometry. In: H. CRAIG, S. L. MILLERand G. J. WASSERBURG (Editors), Isotopic and Cosmic Chemistry. NorthHolland, Amsterdam, pp. 157-168. PYTKOWICZ, R. M., 1964. Rates of inorganic calcium carbonate nucleation. Preprint. S. R., 1951. The isotope geology of oxygen. Geochim. Cosmochim. Actu, 2: 26-42. SILVERMAN, SILVERMAN, S. R. and EPSTEIN,S., 1958. Carbon isotopic compositions of petroleums and other sedimentary organic materials. Bull. Am. Assoc. Petrol. Geologists, 42: 998-1012. STEHLI,F. G., 1956. Shell mineralogy in Paleozoic invertebrates. Science, 123: p.1031. TAYLOR JR., H. P. and EPSTEIN,S., 1962. Relationship between l80/l6O ratios in coexisting minerals of igneous and metamorphic rocks. 1. Principles and experimental results. 2. Application to petrologic problems. Bull. Geol. SOC.Am., 73: 461480, 675-693. TAYLOR JR., H. P., FRECHEN, J. and DEGENS, E. T., 1964. Distribution of 1 * 0 / 1 6 0 and 13C/12C ratios in coexisting minerals of Pleistocene carbonatites, C02 well gases and well waters from the Laacher See volcanic area, Germany. Ann. Meeting Geol. SOC.Am., 1964, in press. THODE, H. G., WANLESS, R. K. and WALLOUCH, R., 1954. The origin of native sulphur deposits from isotope fractionation studies. Geochim. Cosmochim. Actu, 5 : 286298. UREY,H. C., 1947. The thermodynamic properties of isotopic substances. J. Chem. SOC.,1947: 562-581. UREY,H. C., LOWENSTAM, H. A., EPSTEIN,S. and MCKINNEY, C. R., 1951. Measurement of paleotemperatures and temperatures of the Upper Cretaceous of England, Denmark, and the southeastern United States. Bull. Geol. SOC.Am., 62: 399-416. VOGEL,J. C., 1959. Uber den Isotopengehalt des Kohlenstoffs in Siisswasser-Kalkablagerungen. Geochim. Cosmochim. Acta, 16: 236-242. VONECKERMANN, H., VONUBISCH,H. and WICKMAN, F. E., 1952. A preliminary investigation into the isotopic composition of carbon from some alkaline intrusions. Geochim. Cosmochim. Acta, 2: 207-210. WEYL,P. K., 1958. The solution kinetics of calcite. J. Geol., 66: 163-176. WICKMAN, F. E., 1952. Variations in the relative abundance of the carbon isotopes in plants. Geochim. Cosmochim. Acta, 2: 243-254. WILLIAMS, M. and BARGHOORN, E. S., 1963. Biogeochemical aspects of the formation of marine (Editor), Organic Geochemistry. Macmillan, New York.N.Y., carbonates. In: I. A. BREGER pp.596604. ZARTMAN, R. E., WASSERBURG, G. J., and REYNOLDS, J. H., 1961. Helium, argon and carbon in some natural gases. J. Geophys. Res., 66: 277-306.

Chapter 6 INFLUENCE O F PRESSURE AND TEMPERATURE ON LIMESTONES BERNARD L. MAMET AND MICHELINE D'ALBISSIN

Fonds National de la Recherche Scientifque. Laboratoire de Gkologie, UniversitC Libre de Bruxelles, Bruxelles (Belgium) Centre National de la Recherche Scientifque, Laboratoire de Gkologie dynamique, Facultt des Sciences, Paris (France)

SUMMARY

Some of the petrographic and physical characteristics of limestones which have been exposed to increasing temperatures and pressures are reviewed in this chapter. They are first considered under burial load on a moderate scale, with conditions being of the order of magnitude of slightly deformed rocks usually encountered in stable cratons or parageosynclines. Then, the behavior of the carbonate rocks is examined under oriented stress at low temperature; such conditions are well exemplified in alpine-type orogenies. Finally, contact and general metamorphism are studied; they deal with pressures reaching 5,000 atm. and temperatures of 150-700"C.

SEDIMENTATION AND DIAGENETIC FABRICS

Before reviewing the influence of physical variables on limestones, it is important to review a few basic facts concerning limestone formation, because calcite aggregates display properties somewhat different from those of the ideal Iceland spar crystal.1 Limestones are indurated or lithified rocks containing more than 50% calcium carbonate. This induration suggests that the fabric of the assemblage differs from the original fabric; lithification implies diagenesis (the different stages through which aragonite and calcite muds reach equilibrium) but not necessarily recrystallization. It should be noted that petrographers and metallographers often use recrystallization in different senses. If the original dimensions of the crystals remain unmodified and if no nucleation centers appear, one may hardly speak of recry1 Dolomites are not included in this chapter; although their behavior is rather similar to that of limestones, quantitative data are still inadequate to reach definite conclusions. The influence of small amounts of magnesium on calcite assemblages is considered whenever possible.

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stallization but only of phase transformation. The term recrystallization should really be reserved to designate obliteration of original fabric, through displacement of grain boundaries. In such a case the pre-existing texture may still be recognizable as “phantom” or “palimpsest”, or may be totally destroyed. The newly formed assemblage has a lower free energy than the original one. The original matrix in numerous limestones is made up of fine-grained aragonite crystals of micron dimensions. It encloses discrete elements which can be divided into three main groups: fossils, oolites and intraclasts. Diagenesis usually converts the matrix to a stable aggregate. Depending on pcoZ,nucleation, and accretion speed, a microcrystalline mud may remain of the micron size and form an interlocking mosaic of crystals (micrite). In contrast, recrystallization leads to much bigger crystals; it may occur simultaneously with sedimentation (“alpha sparite” parrim) or at a later time (“gamma sparite”) (MAMET,1961). Another possibility is that the closely-packed discrete elements lack micrite matrix at the time of deposition; however, they form a mechanically stable assemblage which may, or may not, be cemented by percolating solutions. The latter product is referred to as void-filled sparite. A first conclusion may be drawn from this brief outline: from purely chemical causes, without external pressure or temperature changes, limestones may vary from those having homogeneous fabrics, with mosaic texture of the micron size (e.g., “Marbre Noir”, MAMET,1964), to those with completely heterogeneous textures where grain-size differences may be of the order of 1-105. INFLUENCE OF LOAD PRESSURE

Load pressure applied on a calcite assemblage increases its strength and stability1 (GOGUEL, 1943; HANDINand HAGER,1957-1958). The primary effects of deformation are compaction, pore reduction, and development of contact surfaces between the grains. These grains become completely xenomorphic2 and the order of magnitude of their size differences decreases to an average of 1-103. It is hard to find a direct and simple quantitative relationship between petrography and burial depth, at such low pressures. The great heterogeneity of the original material, inherited from sedimentation conditions, has already been stressed. Moreover, minute differences in chemical composition lead to extremely variable petrographic “landscapes” (i.e. microfacies). The presence of less than 2 % MgO in the latter is sufficient to induce extensive recrystallization. In contrast, a small percentage of clay readily prevents such a modification. These chemical and sedimentation characteristics often carry through the entire formation. Hence, This pressure may be considered as hydrostatic. Anhedral.

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

21 1

by examining Lower Carboniferous carbonate sequences of northern France and Belgium, the writers were able to recognize a number of persistent crystalline calcite assemblages, which persisted almost independently of tectonic conditions; these latter ranged from burial under about 1,OOO m of sediment to dynamic modification under small load. However, for thrust faults under load, persistent recrystallization patterns (e.g., recrystallization “fibrous sparite”) were detected. Increasing pressure diminishes the depositional differences; unfortunately petrographic recrystallization fabrics are of questionable value at the present time, because there is considerable difference of opinion as to their quantitative significance (BATHURST,1959; ORMEand BROWN,1963). Precise examination of microfossil walls, however, may lead to a fair recrystallization appraisal; these walls exhibit different calcite fabrics, the reactivity of which varies greatly in response to external conditions. Moreover, through morphological and paleontological examination, one can determine exactly from which material the actual assemblage is derived; and thus the approximate amount of recrystallization may be ascertained. The writers have found, for instance, in European Carboniferous limestones: (1) fine-grained, dense, “isotropic” micrite of the pre-Fusulinid wall type (Eostafella); (2) micrite (Endothyra, Bradyana) or agglutinated calcite grains in such material (Forschia);and (3) radially oriented clear microspar on a microcrystalline basal layer (Archaediscus) (W.W. Brown, personal communication, 1964). Careful investigation of such assemblages in similar petrographic environments reveals the same order of texture obliteration, the radially oriented microspar being the last to recrystallize. By comparing the total assemblage of such microfossils in similar facies (same magnesium and clay content, in the same microspar range) and eliminating the otherwise dominant sedimentation factor, one may obtain a clue to the influence of increasing pressure. The same line of thought may be applied to the study of other microfossilbearing sequences. Inasmuch as this type of investigation is long and painstaking one may conclude that a method based on selective oxidation (TEICHMULLER et al., 1960) of the ubiquitous kerogen may be a more convenient geological tool in evaluating burial depth.

INFLUENCE OF STRESS

If pressure increases further, with dynamic modification, calcite crystals respond and WEISS, to the stress by acquiring a preferred orientation (SANDER,1930; TURNER 1963).

Mechanism of the deformation Plastic strain may be related to the concurrent effects of ( I ) intracrystalline gliding

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by twinning or translation; (2) intercrystalline gliding along intergranular boundaries; and (3) recrystallization. Intracrystalline gliding Intracrystalline gliding occurs by a step-by-step process, which induces defects or dislocations between the glided parts. Whereas creation of such defects in pure crystals requires high energies, natural carbonate lattices show many defects which can be displaced and grouped. This process, leading to a distortion of the lattice, raises its potential energy. Twin-gliding. Twin-gliding is the most obvious, but not necessarily the most efficient mechanism for orienting crystals (positive e gliding on 0112) (TURNER and WEISS,1963). Twin-gliding results in petrographic modifications which can be studied under the microscope; this induced early workers to attach paramount importance to the mechanism.1 Further experiments, however, have shown that translation gliding is as likely to induce permanent deformation. Translation gliding on r (0111)2. Extensive gliding on r leaves no visible traces except random orientation of twin lamellae, which usually does not survive minor post-tectonic adjustments (TURNER and WEISS,1963). In tercrystalline gliding Experiments of ADAMSand NICHOLSON (1901) have shown that intercrystalline gliding occurs during plastic deformation; it is an intergranular rupture followed by immediate “healing”. Moreover, the contact of “mosaic calcite” crystals is not planar, but is along an S dislocation family3. In spite of their small volume (HABRAKEN and GREDAY,1956), boundaries act as barriers for dislocation propagation. Recrystallization Recrystallization occurs by (I) solution and precipitation linked to pressure, or (2) formation of new crystal nuclei within the aggregate. Solution and precipitation linked to pressure. The sometimes misquoted “Riecke’s principle” effects are often observed by petrographers. The outlines of a crystal The “mean spacing index” is the number of lamellae encountered per millimeter, in a direction perpendicular to the lamellae plane. It can not be related to the effectiveness of the stress orientation. 2 Another translation off1 has been described for artificially deformed limestones, but it would be effective only in the deepest catazone. Some authors ( L m m , 1957) have proposed the presence of a fluid phase between the mosaic boundaries. 1

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

213

surrounded by a saturated solution of its own composition change; under pressure, strained faces are dissolved, whereas epitaxial growth occurs on the faces under minimal stress.l There is, therefore, a competition among coexistent grains, and the original orientation determines their increase or decrease in size. Formation of new crystal nuclei within the aggregate. Syntectonic recrystallization from a nucleus leads to more or less lenticular grains, with rather regular outlines and no cataclastic effects. The order of magnitude of grain-size differences range from 1-10 to 1-102. Few to no original micrite grains areencountered, but palimpsest textures are still conspicuous. Experimental data have shown that this recrystallization can lead to the formation of rocks similar to natural “marbles” at temperatures as low as 300°C (GRIGGS et al., 1960). Post-tectonic recrystallization of calcite assemblages will first affect the most deformed zones. Grains having many faces with concave boundaries show a tendency to grow, while grains with few boundaries tend to disappear. The limits of grains often coincide with lamellae or twin-glides, which have acted as barriers during the process. Conclusion on the mechanism of the deformation Whatever the proposed mechanism, gliding or recrystallization, the result from a geological point of view is quite similar; the optical axes of the reoriented crystals are in a direction roughly parallel to the maximum stress and plastic deformation increases the stored energy within the lattice. Experimental analysis of the deformation

The oldest method for the evaluation of crystal orientation is that of the universal stage developed by SCHMIDT (1925) and SANDER (1930). It has proved invaluable in many cases of macrocrystalline aggregates. TURNERand WEISS(1963) have shown, however, the difficulties of relating petrography to the probable stress action. Moreover, petrographical approach is hard to apply to microspar, where the grains have sizes comparable or inferior to the thickness of a thin-section. Attempts have been made, therefore, to overcome the difficulties of Sander’s method by investigation of other characteristics. linked to the anisotropy of calcite rhombohedra. Such methods are either vectorial and deal with crystalline orientation-(I) infra-red spectroscopy, (2) dilatometry and (3) X-ray diffraction -or are linked to a direct evaluation of lattice disorder-(l) etching figures and (5) thermoluminescence.

Poynting’s law has been proposed as appropriate here (BARTH, 1962); however, the thermody1960; KAMB, 1959, 1961). namic treatment is still inadequate (MACDONALD,

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B. L. MAMET AND M.

D’ALBISSIN

B 650

900

vcm-

Fig.1. Stress-oriented Guillestre marble. A. Gamier River, Guil Valley, near Guillestre, HautesAlpes, France. B. South of La Chapelue, Hautes-Alpes, France.

Infra-red reflection spectroscopy HAAS(1956) has shown that the reflection spectrum of the extraordinary p r a y at 875 cm-l varies in intensity according to its orientation with respect to the calcite crystal. When the light is parallel to the optical axis, reflection is minimum; whereas when the light is at 90°, reflection is maximum. This method may be applied to calcitic aggregates, and differences in intensities allow rapid determination of the mean orientation (D’ALBISSIN,1963). Some results dealing with strongly oriented microcrystalline aggregates (obtained in the “Zone BrianConnaise” of the Alps) are presented in Fig. 1. Dilatometry The linear thermal expansion coefficient is a property of the lattice (Mitscherlich) and varies according to the orientation of the crystalline structure. The expansion whereas that perpendicular coefficient along the optical axis of calcite is 31.6 to the same axis is -4.2 *lo-6 (D’ALBISSIN et al., 1960). Dilatometers or microstrain gauges readily enable a quantitative measurement of the expansion ellipsoid and, therefore, reconstruction of the deformation ellipsoid. The method is simple, reproducible and most adequate for routine examination. X-ray diflraction As early as 1930, SANDER and SACHSshowed that the X-ray diffraction planes were more important in some directions than in others for aggregates showing preferred orientation. Whereas the Debye-Scherrer method was not accurate enough for detection of such small variations, diffractometry is readily applicable to the variations in intensities observed for a given reflection (HIGGSet al., 1960; D’ALBISSIN and ROBERT,1962).

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

215

Etching figures If it is assumed that a direct relation exists between the number of dislocations and the etching figures (FRIEDEL,1956; D'ALBISSIN,1963), their density per grain can be related to intracrystalline gliding. Although the number of performed experiments is insufficient to prove this, the limited results obtained are in agreement with the proposed scheme. One finds an abnormally high number of corrosion pits in highly laminated microspars (up to 13 patterns per square p as compared to less than 0.01 per square ,n for Iceland spar crystals). Thermoluminescence The energy absorbed during dynamic metamorphism can be dissipated as heat, it may be used to displace the dislocations, or it can be stored within the crystal by distortion of its lattice. Furthermore, it may also be used for recrystallization or solution. A very small amount is used by the electrons which are kept in an excited state, in the highest parts of the forbidden band, through lattice defects. By thermal stimulation, it is possible to liberate such captive electrons and to drive them to a lower energy state with light emission. This phenomenon, called thermoluminescence, is extremely sensitive to the lattice defects and may, therefore, help in the evaluation of stress deformation by intracrystalline gliding. Experiments have shown that thermoluminescence of limestones is restricted to threemain peaks, viz., A peak-235-270 "C, B peak-280-330 "C, and C peak-350-380°C. All undeformed rocks show obvious A and C peaks. Moderate artificial pressure (ZELLER,1954; DEBENEDETTI, 1958) applied to carbonates increases the C peak and decreases the A peak intensity. When pressure reaches 2,000 atm, a new B peak appears (HANDIN et al., 1957). Thermoluminescence of field specimens has shown reasonably good agreement with experimental data. For instance, the patterns presented in Fig.2 are those of Upper Cretaceous sediments from the

zoo

IOO

LOO

Temperature

sm

Fig.2. I. Undeformed Guillestre marble. 2. Laminated Guillestre marble. 3. Laminated and recrystallized Guillestre marble.

216

B. L. MAMET AND M.

D’ALBISSIN

“Sub-Brianconnais” of the Alps. Such curves have been observed in numerous analogous tectonic zones (D’ALBISSIN, 1963) and one may infer that thermoluminescence can be applied to stress evaluation. Geological results The writers have reviewed the different physical approaches which allow appraisal of calcite orientation and hence may lead to estimation of stress pressures. The objection of GOGUEL (1952), who felt that pre-tectonic petrofabrics could be superimposed by stress re-orientation, should be kept in mind, however. This approach is theoretically exact; and investigations should be limited to former homogeneous micrites as described in the introduction. In dynamic metamorphism, palimpsest textures are readily distinguishable and such discrimination is feasible. But when it is no longer possible to recognize the original nature of the rocks, Goguel’s objection must be considered. Stress action can be synthesized in the study of the Alpine orogenic belt. Results are in close agreement with paleo-tectonic history of this chain (Fig.3). Rocks subjected to a feeble load (Sub-Alpine) grade into rocks which have undergone severe thrust action under loads of approximately 2,500 m (Sub-BrianGonnais). In the latter case, the effects of regional metamorphism (epizone) are superimposed on the effects of oriented stress pressure. It is obvious that stress-oriented rocks grade into formations subjected to contact or regional metamorphism, which also display preferred orientation of various intensities. Lack of sufficient data concerning the environment of such metamorphism makes difficult the appraisal of plastic deformation. Attention is, therefore, directed to the formation of new mineral phases in the carbonate assemblages at higher temperatures.

CONTACT METAMORPHISM

Bowen’s progressive thermal decarbonatization series is widely used (STRUVE, Dynamic metamorphism

?!

Sub-Brianconnais

I

Ultra-Brianconnais Ultra-Hclv6tiC

I

Fig.3. Degree of re-orientation of calcite with increasing dynamic metamorphism.

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

217

1958; CALLEGARI, 1962), and can now be found in any textbook of metamorphic petrography. Dolomite, quartz and water lead to the formation of talcl; talc and calcite form tremolite; and the latter with dolomite yields forsterite. These are followed by diopside, brucite, and wollastonite (DANIELSON, 1950; HARKER and TUTTLE,1955, 1956). Higher members have been described by BOWEN(1940) and TILLEY (1951) as shown in Table 1. Successive authigenic minerals occur at given temperatures but an increase of as little as 200 bars in the COZpressure raises the required temperatures by 2OO0C2. Magnesium present in many natural limestones leads to the completion of the series. Bowen’s stages can be observed, therefore, not only in dolomites, but also in the great majority of carbonates. The first steps of Bowen’s series can successfully be checked in contact metamorphism where the system can be regarded as “open”. For higher temperatures, however, the monticellite-larnite series can be contracted. BURNHAM (1959) has shown that spurrite may be derived directly from calcite and silicate without passing through the “low-temperature” steps. From a petrographic point of view, calcite twin gliding on e is conspicuous, and the lamellae are often bent; undulatory extinction or crystal clouding is widespread. REGIONAL METAMORPHISM

The lower boundary of the regional metamorphism is difficult to draw, because stress-oriented rocks grade into it with increasing temperature; however, authigenesis of minerals such as chlorite, epidote or albite is considered as indication of greenschist facies or epizone according to other schools of thought. The last remnants of original carbonate textures may extend rather deep into regional metamorphism. Pentelikon marble’s Macroporella is one example (MARINOS and PETRASCHEK, 1956). One should also note the exceptional and puzzling case of the Cretaceous “Marbres chloriteux” (RAGUIN,1925; ELLENBERGER, 1958), where limestones associated with glaucophane schists3 show such clear palimpsest texture that specific determination of the enclosed microfossils is possibie4. Normally the last phantoms disappear in the epizone; lepidoblastic grains are still encountered, whereas e twin glides are rarely distorted. In m&sozone, the granoblastic texture is dominant and size variations of the order of 1-10 are The presence of talc is often misleading because it is often derived through hydrothermal alteration. 2 Theoretical calculations based on the Clapeyron formula (WEEKS, 1954; LAFFIITE,1957) differ from experimentalcurves; the discrepancy is probably due to the slow equilibriumspeed. Aragonite is the stable form of carbonate in glaucophanite schists facies (JAMIESON, 1953). Another striking example of palimpsest texture is found in pneumatolysis. The case of the and MACGREGOR, datolite-bearing Lower Carboniferous limestones may be noted (PHEMISTER 1942).

218

B. L. MAMET AND M.

D’ALBISSIN

TABLE I APPLICATION OF BOWEN’S SERIES TO OPEN AND CLOSED CARBONATE SYSTEMS

Contact metamorphism open system (“C)

mineral facies

talc tremolite

200

forsterite

250-(330)2

albite epidote

diopside

300

hornblende hornfels

brucite wollastonite

315 450

pyroxene hornfels

periclase monticellite

560 600-800

sanidinite

tremolite contact limestone forsterite contact limestone diopside contact limestone pencatite-predazite wollastonite contact limestone periclase tactite monticellite. . . tactite or xenolith

G E

2 * .Y * cdd T 8

$ 8

$5

sg

58

~~

akermanite ti1 leyite spurrite hankinite merwinite larnite 1 2

Italian term for regionally metamorphosed limestones. Calculated value.

normal. Mortar texture (GRUBENMAN, 1910) and wandering or undulatory extinctions are conspicuous. Cataclasis occurs, while distorted e lamellae are developed. Granoblastic textures are encountered in the deepest part of the almandineamphibole facies and probably in granulite facies. Characteristics of such “catamarbles” are poorly known. Some have been confused with carbonatites (Kaiserstuhl), and the confusion is still to be found in the literature. It is often said that metamorphic limestones react quite differently from the surrounding silicate-bearing rocks (“selective metamorphism”). Whereas this is probably true for extensive metasomatism, careful review of literature shows that this is not so for regional metamorphism. Pure calcium carbonate is indeed one of the minerals most stable with respect to pressure and temperature modifications, but rocks are never devoid of impurities. As little as 1 % of such impurities gives rise to a mineral facies similar in all respects to that of the surrounding silicate

219

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

Regional metamorphism closed system (“C) 200

atm.

“epi-marble” cipolinl tremolite cipolin or “marble” forsterite cipolin or “marble” diopside cipolin or “marble” scapolite “cata-marble”?

1,000 atm.

mineral facies 2,000

arm.

epi

greenschists almandine

500

550

620 700

rocks. Should this have not been the case, the whole concept of metamorphic facies would have required revision. Bowen’s decarbonatization series is of little use in regional metamorphism, because one is rarely certain of the validity of the “closed system” assumption. Formation of tremolite in such a “closed system” with a burial depth of as little as 2,000 m requires mesozone conditions, and for deeper burial postulates catazone environment. If Bowen’s series is of little value in the case of slight metamorphism, it is still a good indicator of the temperatures occurring in the most severe conditions, The most advanced mineral of the series encountered with certitude is diopside, and one may, therefore, reasonably assume a maximum temperature of 600-700 “C for the deepest-seated regional metamorphism affecting carbonates. Oriented stress in regional metamorphism is hard to decipher. Limestones of epi- and mesozone show quite variable preferential orientation ranging from fully oriented to nearly isotropic fabrics. Moreover, dislocations are still abundant.

220

B. L. MAMET AND M. D'ALBISSIN

CONCLUSIONS

Influences of pressure and temperature are hard to estimate because they may have affected rocks at different intervals; each time, they modified the crystal size and shape, preferred orientation, intensity of dislocation, and hence, the mechanical properties of the aggregate. Moreover, these stages may be obscured by posttectonic recrystallization. Recent developments, however, have indicated a series of different approaches which allow a valid appraisal of the geological history of the carbonates. ACKNOWLEDGEMENTS

The authors are indebted to Prof. J. Michot for careful review and constructive criticism of the manuscript. REFERENCES~

ADAMS,E. and NICHOLSON, J., 1901. An experimental investigation into the flow of marble. Phil. Trans. Roy. SOC.London, Ser. A, 195. BARTH,T., 1962. Theoretical Petrology. Wiley, New York, N.Y., 416 pp. R., 1959. Diagenesis in Mississippian calcilutites and pseudobreccias. J. Sediment. BATHURST, Petrol., 29: 365-376. BOWEN,N., 1940. Progressive metamorphism of siliceous limestones and dolomites. J. Geof., 48: 225-275. BURNHAM, C., 1959. Contact metamorphism of magnesian limestones at Crestmore, California. Bull. Ceol, SOC. Am., 70: 879-920. CALLEGARI, E.. 1962-1963. La Cima Uzza. Consiglio Nazionale delle Ricerce, Centro per le studio delle Alpi, Padova, I : 116 pp.; 2: 127 pp. CORDIER, P., 1868. Description des Roches Constituant I'l?corce Terreslre. Dunod, Paris, 553 pp. D'ALBISSIN,M., 1963. Les traces de la dtformation dans les roches calcaires. Rev. Giograph. Phys. Giol. Dyn. Sir. 2, 5 : 1-174. D'ALBISSIN,M. et DE RANGO,C., 1962. etude de la microstructure des roches calcaires par I'observation au microscope klectronique. Bull. SOC.Franc. MinPral. Crist., 85: 170-1 76. D'ALBISSIN, M. et ROBERT,M., 1962. Apprkiation du degre de deformation naturelle au moyen d'un diffractometre. Compt. Rend., 254: 1123-1 125. G. et TONGIORGI, E., 1962. Modifications apportks aux DALBISSIN, M., FORNACA-RINALDI, courbes de thermoluminescence des roches calcaires par une pression orogknique. Compt. Rend., 254: 2804-2806. H., 1960. etude par la mkthode dilatomktrique de D'ALBISSIN, M., SAPLEVITCH, A. et SAUCIER, la dkformation des roches calcaires. Compt. Rend., 251: 2995-2997. DANIELSON, A., 1950. Das Calcit-Wollastonitgleichgewkht.Geochim. Cosmochim. Acta, 1 : 55. DEBENEDETTI, A., 1958. O r mechanical activation of thermoluminescence in calcite. Nuovo Cimento, 7: 251-254. ELLENBERGER, F., 1958. etude geologique du pays de la Vanoise. Mim. Carte Giol.France, 1958: 561 pp. FRIEDEL, J., 1956. Dtformation plastique et dislocations. Cahier Groupe Franc. dudes Rhiof., 3: 17-22. 1

For Russian publications see SMOLIN (1959).

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

22 1

GOGUEL, J., 1953. Importance des facteurs physico-chimiques dans la deformation des roches. Congr. Gdol. Intern.,Compt. Rend.,l9e., Algiers, 1952, 3: 133-142. GRIGGS,D., TURNER, F. and HEARD, H., 1960. Deformation of rocks at 5W800”C. Geol. SOC. Am., Mem., 79: 39-104. GRUBENMAN, U., 1910. Die Kristallinen Schiefer. Borntraeger, Berlin, 298 pp. HAAS,C., 1956. Vibration Spectra of Crystals. Thesis Univ. of Amsterdam, Amsterdam. Unpublished. HABRAKEN, L. and GREDAY, T., 1956. Sur les modes de deformation dans les metaux. Rev. Universelle Mines, 12: 38-55; 209-227. HANDIN, J., HIGGS,D., LEWIS.D. and WEYL,P., 1957. Effects of gamma radiation on the experimental deformation of calcite and certain rocks. Bull. Geol. SOC.Am., 88: 1203-1224. HANDIN, J. and HAGER,R., 1957-1958. Experimental deformation of sedimentary rocks under confining pressure. Bull. Ceol. SOC.Am., 41: 1-50; 42: 2897-2934. HARKER, A., 1952. Metamorphism. Methuen, London, 380 pp. R. and TUITLE,O., 1955. Studies in the system CaO-MgO-Cot. Am. J . Sci., 25:3 HARKER, 209, 274. HARKER, R. and TUI-TLE,O., 1956. Experimental data on the p C 0 ~ - Tcurve for the reaction calcite+quartz. Am. J . Sci., 254: 239. M. and GEBHART, J., 1960. Petrographic analysis by means of X-ray HIGGS,D., FRIEDMAN, diffractometer. Geol. Soc. Am., Mem., 79: 275-292. HOLMES, A., 1920. The Nomenclature of Petrology. Murby, London, 284 pp. JAMIESON, J., 1953. Phase equilibrium in the system calcite-aragonite. J. Chem. Phys., 21: 1385. JUNG,J., 1958. Prdcis de PPtrographie. Masson, Paris. 314 pp. KAMB,W., 1959. Theory of preferred crystal orientation developed by crystallization under stress. J. Geol., 67: 153-170. KAME,W., 1961. The thermodynamic theory of non-hydrostatically stressed solids. J . Geophys Res., 66: 259-271. LAPFITTE, P., 1957. Introduction a I’gtude des Roches mdtamorphiques et des Gites mdtallifPres. Masson, Paris, 358 pp. LUCAS,G., 1955. Caracteres petrographiques des calcaires noduleux, A facies ammonitico rosso de la region mediterraneenne. Compt. Rend., 240: 1909. MACDONALD, G., 1960. Orientation of anisotropic minerals in a stress field. Geol. SOC.Am., Mem., 79: 1-18. MAMET,B., 1961. Reflexions sur la classification des calcaires. Bull. SOC.Belge Gdol. Palkontof., Hydrol., 70: 48-64. MAMET, B., 1964. Skdimentologie des facies “marbres noirs” du Paleozolque franco-belge. Mdm. Inst. Roy. Sci. Natl. Belg., 151: 131 pp. W., 1956. Laurium. 4. Geological and Geophysical Research MARINOS, G. and PETRASCHEK, Institute, Athens, 246 pp. MICHEL,R., 1953. Les schistes cristallins du Massif du Grand Paradis et de Sesia-Lanzo. Sci. Terre, I : 1-287. ORME,G. and BROWN,W., 1963. Diagenetic fabrics in the Avonian limestones of Derbyshire and North Wales. Proc. Yorkshire Geol. Soc., 34: 51-66. PHEMISTER, J. and MACGREGOR, A., 1942. Note on a datolite and other minerals in a contact altered limestone at Chappel Quarry. Mineral Mag., 26: 275-282. RAGUIN, E., 1925. Decouverte d’une faune de foraminifkres dans les calcaires hautement metamorphises du Vallon de Paquiers, pres de la Grande Motte. Compt. Rend., 181: 726-728. SANDER, B., 1930. Gefugekunde der Gesteine. Springer, Berlin, 352 pp. B. and SACHS,G., 1930. Zur rontgenoptischen Gefugeanalyse von Gesteine. Z. Krist. SANDER, Mineral. Petrog., Abt. A., Z . Krist., 75: 550-571. SCHMIDT, W., 1925. Gefugestatistik. Mineral. Petrog. Mitt., 38: 392-423. SMOLIN,P. P., 1959. Principes d’une classification ration+e des roches carbonatks metamorphiques. Izv. Akad. Nauk S.S.S.R., Ser. Geol., 12: 14 pp. STRUVE,S., 1958. Data on the mineralogy and petrology of the dolomite-bearing northern contact zone of the Qukrigut granite. Leidse Geol. Mededel., 22: 235-349.

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TEICHMULLER, M., KALIFEH, Y. and Lows, M., 1960. Transformation de la matiere organique. Rev. Inst. Franc. Pitrole Ann. Combust. Liquides, 15: 1567. TILLEY, C., 1951. A note on the progressive metamorphism of siliceous limestones and dolomites. Geol. Mag., 38: 175-178. TURNER, F. and VERHCKIGEN, J., 1962. Igneous and Metamorphic Petrology. McGraw-Hill, New York, N.Y., 694 pp. F. and WENS,L., 1963. Structural Analysis of Metamorphic Tectonites. McGraw-Hill, TURNER, New York, N.Y., 545 pp. WEEKS,W., 1954. Equilibria relations during thermal metamorphism of carbonate rocks. Am. Mineralogist, 39: 349. ZELLER, E., 1954. Thermoluminescence of carbonate sediments. In: H. FAUL (Editor), Nuclear Geology. Wiley, New York, N.Y., pp.180-188.

APPENDIX ON NOMENCLATURE

Although the writers are fully aware of the inadequacies of taxonomic treatments in petrography, they feel that it is not inappropriate to recommend care in the use of the word “marble”. Not only does the word have different meanings for the layman, the field geologist, and the petrographer, but these meanings also widely differ from one country to another. Most European geologists accept the Harker’s definition of marble as “crystalline limestone”, independently of whether it is of sedimentary or metamorphic origin; this definition was used as early as the 18th century. Moreover, “marble” is often used as a formation name for sedimentary carbonate rocks (e.g., “Marbre Noir” of Dinant, MAMET,1964; “Marbre de Guillestre”, LUCAS,1955). The above usage has also prevailed in the United States; but one generation ago, petrographers began to restrict its meaning. According to TURNERand VERHOOGEN (1962) “marbles are metamorphic rocks composed principally of calcite and dolomite”. This definition is also found in some recent European textbooks (JUNG,1958). Replacement of “marble” by a more precise petrographic term is somewhat difficult and is not really desirable. The literature abounds in obsolete forms which should remain in obscurity, even if some of them are rather self-explanatory.1 The authors feel that the term “metamorphic limestone” used by most English petrographers is by no means lengthy and leads to no confusion. If, however, the petrographic use of “marble” is to be applied to metamorphosed carbonates, composite descriptive names are recommended (HOLMES,1920), e.g., epi-, meso-, or cata-marble (GRUBENMAN, 19lo); or forsterite-marble, diopside-marble, etc. The use of “cipolin”2 for muscovite to diopside limestones formed by regional Thermocalcite for contact metamorphic limestones (CORDIER, 1868); or calciphyre for ‘crystalline limestones containing conspicuous calc-silicate minerals such as forsterite, pyroxene and garnet’ (Brongniart in HOLMES, 1920). a A crystalline limestone rich in silicate minerals and characterized by micaceous layers; serpentinization of the forsterite leads to ophicalcite. 1

INFLUENCE OF PRESSURE AND TEMPERATURE ON LIMESTONES

223

metamorphism might also partiaIIy meet our needs; it is, however, rarely if ever used in American literature.

Chapter 7

THE ORIGIN OF PETROLEUM I N CARBONATE R O C K S JOHN. M. HUNT

Department of Chemistry and Geology, Woods Hole Oceanographic Institution, Woods Hole, A.) Mass. (US.

SUMMARY

The hydrocarbons in petroleum appear to owe their origin to different sources and mechanisms. The light hydrocarbons and gases generally containing less than nine carbon atoms are formed in sediments over geologic time from the decomposition of heavier organic materials. The heavier hydrocarbons are synthesized by living organisms and are formed in the sediments. Formation of hydrocarbons appears to continue until the sediments are so metamorphosed that only methane is obtained. Carbonate sediments appear to be as effective source beds as clay sediments although there are differences in the time and conditions of generation, migration, and accumulation of oil. As a result of early lithification of carbonates, hydrocarbons tend to be retained until migration paths are developed through fractures, fissures, and solution channels. The close juxtaposition of source and reservoir beds in carbonates plus the frequent presence of impermeable evaporite caprocks results in a more efficient process of oil accumulation in carbonates than in sandshale sequences. Carbonates, however, have very little catalytic activity compared to clays and they do not continue to expel fluids to reservoirs over long geologic periods as do the clays. The fact that 40 % of the petroleum in major oil fields is in carbonate reservoirs, many of which are completely surrounded by carbonate rocks, indicates that carbonates can be oil source beds.

INTRODUCTION

It has frequently been assumed that petroleum does not originate in carbonate rocks. Present day concepts on the origin and migration of oil, however, do not preclude the possibility of carbonates being source rocks. One of the more important findings of the past decade is that finely disseminated petroleum constituents are indigenous to nearly all types of sedimentary rocks: VASSOEVICH (1955), Woods Hole Oceanographic Institution Contribution No.1577.

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J. M. HUNT

HUNTand JAMIESON (1956) and PHILIPPI (1956). This was predicted some years ago by PRATT (1942), who stated: “Petroleum is an inevitable result of fundamental earth processes, so typical that they have been repeated in each successive cycle of earth history. It is a normal constituent of unmetamorphosed rocks of nearshore origin.” There are certain basic differences in the source and types of organic matter deposited with carbonates as compared to shales. Also, the early lithification of carbonate rocks as compared to the slow compaction of shales would infer different conditions of migration. These factors might alter the composition of oil and its time of migration, but they would not prevent it. The wide range of environments of deposition of carbonate rocks would allow adequate quantities of organic matter to be retained for the generation of oil. Many studies of both Recent and ancient fine-grained carbonates have shown them to contain hydrocarbons in amounts comparable to clay sediments. Approximately 40% of the estimated 217 billion barrels of oil from major fields outside the Soviet Union and related Socialist republics are in carbonate reservoirs (KNEBEL and RODRIGUEZ-ERASO, 1956). In view of the fact that some of these reservoirs are completely surrounded by carbonate rocks, one must assume that carbonates can generate petroleum.

ORIGIN OF PETROLEUM

Petroleum is a complex mixture of hydrocarbons with molecular size ranges from 1 to over 40 carbon atoms, the predominant molecular types being paraffins, naphthenes (cycloparaffins), and aromatics. In addition, petroleum contains small amounts of oxygen, nitrogen and sulfur compounds called asphaltics plus traces of metallic salts. Table I shows the composition of what might be regarded a typical crude oil, although it should be emphasized that crude oils vary tremendously in composition. Some oils show large variations in composition within the same reservoir. Nearly all petroleum is believed to have an organic source, that is, it was formed from organic matter that was once part of a living organism. The different fractions of petroleum, however, may have been formed by different processes. As postulated by HUNTand JAMIESON (1956), the origin of petroleum appears to be a dual process: part of the oil originally being deposited with’ the sediments as a product of living organisms, and part being formed in the sediments after burial from the reduction of non-hydrocarbon organic material. Hydrocarbons.from living organisms

Many hydrocarbons and related organic structures have been identified in both

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

227

TABLE I COMPOSITION OF A TYPICAL CRUDE OIL

Fraction (molecular size) gasoline (C4x10) kerosene (C11-C12) gas oil (Cls-Czo) lubricating oil ( c 2 1 - c 4 0 ) residuum (> c40) Molecular type parafins naphthenes aromatics asphaltics

31 10 15

20 24

100

30 49 15

6 100

living things and petroleum. These substances have also been found in Recent and ancient sediments, suggesting that they find their way into petroleum purely by an accumulation process with only minor changes in chemical composition. The first structures from living things identified in crude oils were porphyrin derivatives of chlorophyll and hemin, which are the green plant and animal blood pigments, respectively. These were found by TREIBS in 1934. He found the chlorophyll-derived porphyrins to be about 20 times more numerous than those from the hemins. This suggestedthat crude oil originated primarily from plant life. Later, OAKWOOD et al. (1952) concentrated the optically active fraction of crude oils and found it to be a crystalline hydrocarbon with several naphthene rings. Optically active compounds have never been formed except by living things. This was an added evidence that a life process was involved. More recently, BENDORAITIS et al. (1963) isolated from petroleum a whole series of isoprenoid hydrocarbons, and MAIRand MARTINEZ-PICO (1962) isolated a hydrocarbon with the steroid nucleus. Both the isoprenoid and steroid structure are common in living things. The presence of hydrocarbons in living things has been known for some time. CHIBNALL and PIPER(1934) made the most detailed studies of paraffin hydrocarbons in insects and plant waxes. They were the first to discover a predominance of alkanes with odd carbon number chain lengths in the c 2 5 - c 3 7 range. WHITMORE (1945) postulated from his studies of the hydrocarbons in kelp that the quantities of hydrocarbons formed by life processes were sufficient to account for all the peand GERARDE (1961) published troleum in the world. More recently, GERARDE a detailed summary of all the hydrocarbons known to be in living organisms. Among the paraffin hydrocarbons, methane is the most common and is produced

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J. M. HUNT

primarily in marshes where bacteria are metabolizing organic matter. No hydrocarbons from ethane through octane (CZ-CS)are known to be formed biologically, except possibly heptane. Paraffin hydrocarbons containing nine or more carbon atoms, particularly the waxes in the molecular weight range c23-c37, are quite common in nature. Naphthenes with less than ten carbon atoms do not occur in living organisms. Most of the cycloparaffins occur as unsaturated terpenes ( C ~ Hl6). O The naturally occurring aromatic hydrocarbons start with ten carbon atoms and go up into the higher molecular weight ranges. The most common is paracymene which is widely distributed in spices. The presence of high molecular weight hydrocarbons in marine organisms has been studied by BERGMANN (1 949, 1963), who first observed that the unsaponifiable fraction of invertebrate lipids was higher in the more primitive animal forms. This suggested that waxes, sterols, and hydrocarbons are most prominent in the lowest and most primitive forms of life. BLUMER et al. (1964), BLUMER and THOMAS (1964), and BLUMER and OMAN(1965) have isolated pristane and a whole series of hydrocarbons related to phytol from marine zooplankton. The first isolation of liquid hydrocarbons from Recent sediments was by SMITH(1954) who found a series of paraffin, naphthene, and aromatic hydrocarbons heavier than c14 in Gulf Coast muds. He was able to date them by radiocarbon methods at about 10,000 years. A more detailed study by MEINSCHEIN (1961) showed a large number of hydrocarbons having more than 14 carbon atoms to be present in Recent sediments. It should be emphasized that the hydrocarbons identified by the aforementioned workers in living things and in Recent sediments represent only a very small fraction of petroleum in the higher molecular weight range (above c14). SOKOLOV (1957) and VEBERand TURKELTAUB (1958) stated that their studies of hydrocarbons from the sediments of the Caspian Sea and Black Sea, which are rich in organic matter, showed no hydrocarbons in the CZ-c14 range. They pointed out that the hydrocarbons in Recent sediments cannot represent petroleum because the missing fractions up to c14 constitute up to 50% or more of many crude oils. EMERY and HOGGAN (€958) had previously reported finding a total of less than 1 p.p.m. of these hydrocarbons in sediments of the basins off the California coast. J. G. Erdman (personal communication, 1962) found only methane and heptane in the Cl-C, range of Recent sediments, whereas in ancient sediments he found all the saturated hydrocarbons including pentanes: hexanes, heptanes, etc. ERDMAN et al. (1958) had previously reported that the low molecular weight aromatic hydrocarbons, benzene and the xylenes, also are absent from Recent sediments. DUNTONand HUNT(1962) found the C4-cS hydrocarbons to be absent from 21 Recent sediment samples from Venezuela, Texas, Cuba, California, and Norway. Twenty-nine ancient sediment samples ranging in age from Precambrian to Miocene, however, yielded c 4 - c S hydrocarbons in amounts ranging from 1 to

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

229

over 800 p.p.m. These studies show that hydrocarbons lighter than nonane (Cg) are generally absent in Recent sediments. It has also been found that there are fewer heavy hydrocarbons in Recent sediments than in ancient sediments. HUNT(1961) analyzed 55 Recent sediment samples from six different areas and found only one of them to contain as many hydrocarbons above C14 as the average of 1,000 ancient sediments. Most of the Recent sediments contain only about 1/5 as many hydrocarbons as the ancient sediments. In summary, it appears likely that some of the hydrocarbons in the high molecular weight range of petroleum are synthesized by living organisms and eventually become crude-oil accumulations with only minor changes. All paraffin, naphthene and aromatic hydrocarbons containing less than nine carbon atoms (except methane and heptane), however, are not synthesized by living organisms, and are not found in Recent sediments. Consequently, these must be generated in the sediments. Also, the fact that Recent sediments contain fewer hydrocarbons above Cg than ancient sediments suggests that part of the whole molecular weight range of hydrocarbons is formed from organic matter in the sediments. Generation of hydrocarbons from organic matter

The basic substances of plant and animal material are the proteins, carbohydrates, and lipids. Higher plants also contain lignin, a high molecular weight aromatic compound. Lignin comprises about 15-20 % of the total terrestrial plant substance on a dry weight basis and would be the major contributor of aromatic structures to petroleum. The proteins, which are the chief source of nitrogen in organic sediments, are complex polymers of amino acids, Cellulose, the most important carbohydrate, is a fundamental constituent of cell walls. Lipid is a general term which includes waxes, fats, essential oils and pigments. Many of the pigments are pure hydrocarbons and can be incorporated in crude oils with only minor chemical changes. SILVERMAN (1962) pointed out that the 13C/12C isotope ratios of petroleum and various organic materials point to the lipids as the primary source of petroleum. In chemical composition the lipids are closest to petroleum as can be seen from Table 11. Any of these constituents may be potential sources of hydrocarbons until proven otherwise. Bacteria, which are common in the first few feet of most sediments, bring about the initial decomposition 6f organic matter. From 10-50% of the organic matter is converted into bacterial cell material. Under aerobic conditions the free products are water, carbon dioxide, and sulfate, phosphate and ammonium ions. Products formed are similar under anaerobic conditions except that sulfur is eliminated as hydrogen sulfide and methane and hydrogen are formed (ZOBELL, 1959). One significant difference between carbonate and clay sediments concerns the depth at which bacterial activity may occur. LINDBLOOM and LUPTON(1961)

230

J. M. HUNT

TABLE I1 AVERAGE CHEMICAL COMPOSITION OF NATURAL SUBSTANCES

Elemental composition in weight %

carbohydrates lignin proteins lipids petroleum

C

H

44

6 5 7 10 12-15

63 53 80 82-87

S

0.1 2 0.1-5

N 0.3 16 0.1-0.5

0 50

31 22 10 0.1-2

found that bacteria living on the organic matter in carbonate muds from Florida and Cuba practically died out within the first five feet of sediments. Clay muds from areas such as the Orinoco Delta and the Gulf of California, however, contained active bacteria at much greater depths. In the former case viable bacteria were found to a depth of about 150 ft. Lindbloom and Lupton suggested that the extreme reducing conditions and the high H2S content associated with carbonate muds such as those from Florida Bay may limit bacterial growth. The average Eh of eleven shallow cores from carbonate muds of Florida Bay and the Gulf of Batabano was -200 mV, whereas some Orinoco Delta clay sediment had a positive Eh even at great depth. The iron associated with clay sediments utilizes H2S to form sulfides, but in pure carbonates relatively free of iron, there is a build-up in H2S content which remains in the sediments even at great depths. This H2S has been found in ancient carbonates which may have little or no organic matter. It may also be a factor in the high suifur content of many oils associated with carbonates. KREJCI-GRAF (1963) stated that the commonly asphaltic nature and high sulfur content (several percent) of oils ,associated with calcareous rocks implies a different mode of origin than that of low (usually under 1 %) sulfur oils from clay sediments. As the organic matter is buried deeper in sediments, the bacterial activity becomes less important and the conversion of organic matter to hydrocarbons proceeds through thermal or catalytic degradation. Catalytic activity requires intimate contact between the organic matter and the mineral surface. Here there appears to be significant differences between carbonate and clay muds. GORSKAYA (1950) noted that as the particle size of Recent clastic sediments decreased, the percent of organic carbon, the total bitumens and the hydrocarbons all increased (Table III). In a study of the Viking Shale, HUNT(1962) found a three-fold increase in the organic content in going from siltstone to clays having particles less then 2 p in diameter as shown in Table IV. The organic matter in clays, associated with the finest particle size, is, therefore, in intimate contact with the mineral surfaces.

23 1

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

TABLE I11 ORGANIC MA'ITER OF RECENT CLASTIC SEDIMENTS

(After GORSKAYA, 1 950) Sediment

organic matter (weight %)

Weight % in organic matter total bitumens' hydrocarbons

sands silts clay muds

0.77 1.15

1.5 2.1

1

1.80

2.8

0.043 0.096

0.141

Organic matter soluble in organic solvents.

On the other hand GEHMAN (1962), in a study of 346 ancient limestone samples, found the carbonate muds to contain 0.18 % organic matter compared to 0.23 % for skeletal grains and 0.10 % for non-skeletal grains. Gehman also found that the organic compound, quinoline, in aqueous concentrations up to 200 p.p.m. was readily adsorbed by the three principal clay minerals, namely, kaolinite, illite, and montmorillonite; whereas no adsorption occurred with lime-mud. Clays have been known for decades to be excellent catalysts in causing rearrangements of carbon groups in organic compounds. FROST(1945) was able to convert alcohols, ketones, and other non-hydrocarbon compounds to hydrocarbons at relatively low temperatures, such as 150-180 "C,in the presence of clays. He found that the montmorillonite- and illite-type clays were quite active, whereas the kaolinites were relatively inactive. More recently, WEISS(1963) reported the formation of cyclic and aromatic hydrocarbons from heating organic complexes of montmorillonites. A particularly interesting study is that of JURG and EISMA (1964), who found that heating behenic acid (C21H4sCOOH) at 200°C in the presence of bentonite with or without water yielded a series of paraffin and olefin hydrocarbons. It is significant that hydrocarbons were obtained in the presence of water, which would be TABLE IV VARIATION IN ORGANIC CONTENT WITH PARTICLE-SIZE IN VIKING SHALE

(After HUNT,1962) Particle size

Organic matter (average weight %)

232

J. M. HUNT

the natural state for oil generation. No hydrocarbons were obtained by heating without the clay. Although more studies of this type are needed, particularly with carbonate muds, it does appear that the clay shales have a distinct advantage over carbonates in generating hydrocarbons by catalytic processes. There is still the possibility for the catalytic generation of hydrocarbons because the small amount of clays is dispersed in many carbonate rocks. USPENSKIY et al. (1949) noted that the organic carbon in carbonate rocks is primarily associated with the clay minerals frequently present in such rocks. The author treated a sample of mud from Florida Bay with dilute hydrochloric acid to isolate the non-carbonate fraction. The latter was then analyzed for organic matter content and compared with the original mud. One sample containing about 15% of clay minerals was found to have 75 % of its organic matter attached to the small clay fraction and only 25 % to the large carbonate fraction. (1 95 1) noted a very clear relationship between USPENSKIY and CHERNYSHEVA the insoluble residue, presumably clays, in carbonate'rocks and the organic matter as shown in Table V. The total organic matter and the bitumen content, which includes hydrocarbons, increased with increasing insoluble residue content. In pure carbonates, where no clays are present, the possibility of catalytic formation of hydrocarbons is remote. The conversion of organic matter to hydrocarbons in pure carbonates is a thermal process. This suggests that somewhat greater depths of burial and longer periods of time are required to generate oil in carbonates than in clays. Consequently, carbonate source beds might not yield oil to reservoirs as early in the history of a sedimentary basin as would the clays.

TABLE V RELATIONSHIP BETWEEN ORGANIC MATTER AND INSOLUBLE RESIDUE OF CARBONATE ROCKS

(After USPENSKIY and CHERNHYSHEVA, 1951) Insoluble residue (weight %)

Organic matter (weight %)

Bitumen' (weight %)

4.3 10.2

0.06 0.15 0.28 0.49 0.70 0.93 2.36

0.015

15.5

24.5 57.9 66.1 72.8 1

0.021 0.034 0.034 0.046 0.05 1 0.052

Organic matter soluble in organic solvents. It contains the hydrocarbons.

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

233

MIGRATION OF PETROLEUM

The primary migration of petroleum involves the movement of oil and gas from the dense, low permeability source sediment into the porous, permeable reservoir rock. Secondary migration is concerned with the movement of petroleum within the reservoir rock. In considering carbonates as possible source rocks, it is important to compare the processes of primary migration as they might occur in carbonates and clays. The most plausible hypothesis is that as the sediments are deposited, the more deeply buried sediments lose their interstitial water under the forces of overburden pressure and compaction. WEEKS(1961) has estimated that from 15-20 billion barrels of fluid is expelled from each cubic mile of mud during compaction of a sedimentary basin. As the fluid passes out of the consolidating sediment it carries with it minute quantities of oil. On entering a porous reservoir rock, the physical and chemical conditions are believed to change sufficiently to cause release of the oil. As the oil droplets increase in size, they are unable to re-enter the fine, water-wet pores of the surrounding dense rock. This is purely a hypothesis and it does not explain how the oil migrates in the water, what portion of it moves with the water, or at what stage most of the oil leaves the source bed. The oil may travel in the form of droplets, as a colloidal dispersion, in solution, or in a gaseous form. HOBSON(1954) has discussed a mechanism by which oil globules may be squeezed between small pore openings, eventually making their way into the reservoir. E. G. BAKER(1962) has presented evidence on petroleum composition, which, according to him, supports the concept of the migration of oil as a dilute colloidal dispersion stabilized by natural soaps. MCAULIFFE ( I 964) made detailed studies on the solubility of hydrocarbons in water. His data suggested that hydrocarbon solubilities are sufficient to account for known oil accumulations. In most sedimentary basins calculations of the total quantity of water moved compared to the oil in place indicate that solubilities of hydrocarbons in water of 2-5 p.p.m. are sufficient to account for the oil fields. There are arguments against all of the proposed mechanisms. Migration of oil as globules would require distortion of the globule in order to move through the very fine pores of the source bed, and such distortion is resisted by the high interfacial tensions. About 50 times more soap or solubilizing material than hydrocarbon is needed for the formation of a colloid, and it is well known that such surface-active agents tend to be adsorbed by the host rock. For example, attempts to use soap solutions for the secondary recovery of oil have largely failed because the soap is adsorbed on the mineral surfaces before travelling very far. Migration either as a colloid or in pure solution does not explain why the oil separates out on entering a porous reservoir. Undoubtedly there are differences in the physical and chemical environment of the reservoir compared to the source bed, but just what these are and how they cause separation of the oil is not known.

234

J. M. HUNT

If oil migrates as fine globules or as colloids it would encounter more difficulty in moving through fine-grained carbonate source beds than through clays. Carbonate particles would not have the mechanical ability of clay particles to cause distortion of the globules and consequent squeezing through the sediment pores. Migration as a soap-stabilized colloid would be stopped by the presence of calcium and magnesium ions in the water. It is generally known that calcium ions in sand columns will tie up surface-active agents, and there is no reason why this would not happen in muds. Migration in solution without the aid of solubilizing organic material would probably occur as readily in carbonates as in clays. GINSBURG (1957) has pointed out that most of the water in carbonatemuds is lost in the first foot or two. WELLER(1959) agrees that very little compaction occurs in lime-muds. HOLLMANN (1962) showed evidence for the underwater consolidation of limestones, and observed that in relatively deep water off northern Italy the undersides of ammonites have impressions of irregularities of the underlying limestone beds. This indicates that the limestone beds were hardened and partly dissolved before the ammonites were laid down. The limestones consolidate mainly by cementation and recrystallization. It would seem from this that the migration of fluids from limestones would occur too early and over too short a depth interval to be an effective mechanism in carrying appreciable quantities of oil to a reservoir. Consequently, most of the oil in a carbonate rock would be locked in and would have to find its way out at some later stage of lithification. This could occur with fluid migration along fractures, solution paths and joints which (1962) observed are much more common in carbonates than in shales. GEHMAN that the ratio of hydrocarbons to organic matter in limestones was much higher than that in shales. This is consistent with the idea that limestones tend to lock in their hydrocarbons and release them with much more difficulty than do the shales. There are other explanations for this, however, which will be considered later. CHAYKOVSKAYA (1960) stated that according to some investigators the early lithification of carbonate muds makes them incapable of giving up bitumens to surrounding formations. Nevertheless, there are evidences of molecular migration within carbonate source beds which are quite numerous and convincing. Chaykovskaya pointed out that bitumens move into the numerous fractures and caverns that are formed by the circulation of underground water through the carbonate rocks, which also increases primary porosity. She concluded that several of the carbonate formations in the Turukhansk and Noril’sk district of the Soviet Union are characterized by high bitumen content. These’bitumens were formed within the carbonate source beds and redistributed themselves in minor caverns, pores and fractures. Chaykovskaya also agreed with Gehman that pure carbonate formations contain a relatively small quantity of organic matter, a large part of which consists of hydrocarbons. It should be emphasized that there are many argillaceous limestones and calcareous shales having mineral compositions between those of the clays and

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

235

carbonates. These are even less understood with respect to their compaction characteristics and ability to release fluids to the reservoirs. Many of these hybrid sediments have very high organic contents (HUNT,1961; BITTERLI, 1963). Some of these, such as the Duvernary Formation of Canada and the LaLuna Formation of Venezuela, appear both chemically and geologically to be source rocks.

EXAMPLES OF CARBONATE SOURCE ROCKS

Recently, OWEN(1964) reviewed the geological concepts favoring carbonates as being source rocks. He stated that the stratigraphic and structural habitats of many oil and gas pools in carbonate rocks indicate indigenous origin of their hydrocarbons. There are many oil-producing areas where carbonate rocks are by far the dominant lithology. Some of the important oil occurrences are discussed in this chapter. The Williston Basin, U.S.A.

This basin covers an area of more than 100 sq. miles and contains a Devonian marine carbonate section more than 1,000 ft. thick (BAILLIE,1955). The strata consist of an assemblage of limestones, dolomites, evaporites and minor amounts of shale. Commercial oil is found in the predominantly carbonate strata of the Saskatchewan group, although both oil shales and asphalt stains are present throughout many parts of the Middle and Upper Devonian. For example, at the base of the Elk point group in northwestern North Dakota and eastern Montana, there is a dark colored, dense limestone that was deposited under euxinic conditions that favored preservation of organic matter. Oil shows and staining are common on fractured surfaces, suggesting that the oil is indigenous, and that the dark limestone can be considered a source rock. Here again, however, it could be argued that clays are contributing some oil, because argillaceous limestones and dolomites are common to both the Middle and Upper Devonian sections. Nevertheless, this does represent an oil-generating area of predominantly carbonate facies. Many of the carbonates of both the Elk Point and Saskatchewan groups are pale to dark brown limestones and dolomites with dark grey carbonaceous shale laminae in places, and oil staining and bitumens are common throughout the section. Abqaiq-Ghawar oil j e l d , Saudi Arabia

The largest oil field in the world, Abqaiq-Ghawar, is on a structural accumulation more than 140 miles long and produces from an oil column reaching a maximum vertical thickness of 1,300 ft. (ARABIAN-AMERICAN OIL COMPANY STAFF,1959). The main producing interval is the Arab-D member in the upper part of the Juras-

236

J. M. HUNT

sic Jubaila formation. The Jubaila consists of 1,200ft. of fine-grained limestone with subordinate calcarenite, limestones and dolomite. The Arab-D formation consists of calcarenite, fine-grained limestone and dolomite with interbedded anhydrite members (560 ft.). This is overlain by another 500 ft. of limestone and dolomite with an anhydrite cover. Above the anhydrite at the base of the Arab-D member the sediments contain only oil shales and minor staining. Most of the oil production found in the first 240 ft. of the Upper Jubaila Formation is below the anhydrite. The Arabian-American Oil Company staff, who have probably studied this field more intensively than any other group of individuals, believe that the Ghawar oil originated in the Upper Jubaila and Arab-D sediments. This is based partly on the apparently capricious distribution of oil and water in porous units of the Middle and Lower Jubaila. The volume of these porous units is roughly proportional to the amount of calcarenite in the formations. This is probably one of the most clear-cut geological examples of carbonate source rocks. Other Middle East ,fields

Other possible carbonate source beds in the Middle East include the Middle Cretaceous to Oligocene limestones and chalk of Iraq, Iran and southeast Turkey with oil in associated reef complexes and fractured limestones (BAKERand HANSON, 1952). Also, the oil fields of southwest Iran produce from the Upper Asmari Limestone which is believed to contain indigenous oil. The Asmari Limestone is 700-1,500 ft. thick and has reef characteristics in places. Both the Miocene and Oligocene components of the Asmari are richly organic. The 60-mile long Kirkuk, a billion barrel oil field in northern Iraq, is another good example of a Middle Eastern oil field with carbonate source rocks (DUNNINGTON, 1958). The producing reservoir is made up of reef and globigerinal limestones of Middle Eocene to Lower Miocene age. Limestone and a salt bed overly it, and thick limestones and marlstones underly it. Miscellaneous examples

There are other examples of oil occurrence in carbonate rocks but in many of these an overlying or underlying shale is a more likely source. One of the most common examples of this is oil occurring at unconformities where shales overly carbonates. Porosity in such carbonates is frequently due to erosion and solution weathering. This provides an excellent reservoir for oil migration from overlying clay muds. Typical examples are the Rogers City, Traverse, and Dundee Limestones of the Michigan Basin and the Trenton Limestone of Michigan and western Ohio. Another is the Simpson Shale acting as a source for the Ellenburger Limestone of the Permian Basin of Texas and New Mexico. MILLERet al. (1958), in a detailed study of the oil in the Maracaibo Basin of Venezuela, concluded that the highly bituminous LaLuna Limestone was a

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

237

probable source for some of the oil in western Venezuela. The effective reservoir section of the Cogollo and La Luna'Limestones is about 1,800 ft. thick. BODUNOVSKVORTSOV (1 958) believed that the bitumens found in the lower Cambrian dolomitic limestones of eastern Siberia were indigenous. There are three carbonate suites, the Angar, Bulay and Bel, which represent about 800 m of limestones interbedded with anhydrite. The whole section is underlain by a thick dolomite sequence. BROD(1959) believed that the asphalts and bitumens found in inclusions of thick Paleozoic limestones and dolomites of the western part of the East Siberian platform are indigenous. There are probably many other examples of carbonate sediments believed to be source beds of oil. Those given here are suficient, however, to attest to the widespread distribution of carbonate sources. As previously mentioned, carbonate rocks contain at least 40 % of the world's oil, although they represent only 16 % of the sediments of the basins of continents and continental shelves compared to 50% for clay shales (WEEKS,1958). Some of the factors which favor formation of carbonate source rocks include the following: (I) It has been stated that the carbonates would lithify quickly and tend to hold in their hydrocarbons during the early stages of fluid migration from a basin. Many hydrocarbons are undoubtedly lost from clay muds during this period due to the lack of a sufficiently impermeable caprock. (2) Limestones are frequently associated with evaporites under conditions that are highly favorable to oil generation and accumulation. WEEKS(1961) cited a typical sedimentary sequence as beginning with a deep stagnant limy mud facies with limestones or dolomites around the flanking shelves. Cherts may occur in the deeper parts, followed by purer, partly recrystallized and dolomitized limestone facies. Isolated reefs facing the deep basin as well as patch reefs higher on the shelf are common. The sequence continues up with spreading evaporites-primary dolomites, anhydrites, and/or salt. Eventually evaporites spread over the entire central area of the basin. In such a cycle the organic matter which accumulated from the beginning eventually generates hydrocarbons on a vast scale. These are then trapped because of the presence of impermeable cover of evaporite deposits. Weeks cited about 20 examples of oil-producing basin sequences that go through some or all of these stages. (3) The hydrocarbons moving with the aqueous phase through fractures, fissures and primary.pores enlarged by solution would tend to be released to form oil globules on contact with the highly saline waters typical of carbonateevaporite sequences. This is speculative, of course, but the great variations in salinities could be a favorable factor in the oil-accumulation process. In summary, it appears that most carbonate source rocks associated with major oil accumulations, such as the huge Tertiary and Jurassic oil pools of the Middle East, are of this carbonate-evaporite sequence type favorable for the origin, migration and accumulation of oil.

238

J. M. HUNT

DISTRIBUTION OF ORGANIC MATTER IN CARBONATE SOURCE ROCKS

Geochemists have approached the identification of source rocks by making detailed studies of the various organic constituents in ancient sediments and finding out differences between oil-producing and non-producing regions. If one accepts the concept that petroleum originates from organic matter deposited with the non-reservoir sediments (dense carbonates) and migrates into reservoirs (reefs, oolites), then it is important to understand the distribution of the organic matter and hydrocarbons in the non-reservoir sediments. The distribution of organic matter in sediments varies widely and is significant in drawing conclusions about the probabilities of finding oil in a particular part of a sedimentary basin. Unfortunately, few studies of this type have been made in carbonate sequences. Much more common are studies of clays with minor amounts of carbonates. For example, RONOV (1958) made a detailed study of the organic carbon distribution in the Devonian sediments of the Russian platform. He found that, in general, the clays contained more organic carbon than the carbonates. His data are shown in Table VI with the organic carbon converted to organic matter by multiplying by a factor of 1.22 (see FORSMAN and HUNT,1958, for conversion factor). As might be expected, the coastal and open-sea environments contained most of the organic matter and the continental the least. Ronov also noted an interesting correlation between the occurrence of petroleum in Devonian reservoirs and the concentration of organic matter in associated non-reservoir rock. He found that all the petroleum was located in regions where the associated shales contained the higher organic contents, generally at least 1 % organic matter. In regions where the organic content of the shales was low (generally less than 0.5 %), no oil or gas was found. Inasmuch as the carbonates were intermixed with the clays, no conclusions can be drawn as to their effect on the oil accumulations. Also, Ronov did not make hydrocarbon analyses which are important in evaluating carbonate source rocks. TABLE VI WANIC MATTER AND ENVIRONMENT (DEVONIAN OF THE u.s.s.R.)

(After RONOV,1958) Environment

Weight % of organic matter1 carbonstes

days

continental, lagoonal coastal-marine open sea 1

Organic carbon times 1.22.

0.43 0.95 1.10

'

0.18 0.25 0.39

239

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

TABLE VII DISTRIBUTION OF HYDROCARBONS AND ORGANIC MATTER IN NON-RESERVOIR ROCKS

(After HUNT,1961) Rock type

Shales Wilcox, La. Frontier, Wyo. Springer, Okla. Monterey, Calif. Woodford, Okla. Limestones and dolomites Mission Canyon Limestone, Mont. Ireton Limestone, Alta. Madison Dolomite, Mont. Charles Limestone, Mont. Zechstein Dolomite, Denmark Banff Limestone, N.D. Calcareous shales Niobrara, Wyo. Antrim, Mich. Duvernay, Alta. Nordegg, Aka.

Hydrocarbons fP,p.rnJ

Organic matter (weight %)

180 300 400 500 3,000

1 .o 1.5 1.7 2.2 5.4

67 106 243 271 310 530

0.11 0.28 0.13 0.32 0.47 0.47

1,100 2,400 3,300 3,800

3.6 6.7 7.9 12.6

The hydrocarbon analysis can be obtained by pulverizing the sediment sample and extracting the soluble organic matter with various organic solvents, such as ether or benzene. The soluble organic matter can be separated into two fractions, the hydrocarbons and the non-hydrocarbons (asphalts), by column chromatography (HUNT,1956; PHILIPPI,1956). Light hydrocarbons are lost in removing the solvent so that the molecular weight range starts a t about c14 and continues on to c40-c50. The asphalts are compounds containing nitrogen, sulfur and oxygen as well as carbon and hydrogen. The residual organic matter, which has sometimes been referred to as kerogen, has been described in some detail by FORSMAN and HUN? (1958). The distribution of the hydrocarbons and residual organic matter in some typical shales and carbonates is shown in Table VII. The hydrocarbon fraction represents petroleum that is disseminated in the source bed. In most sedimentary basins there is 20-100 times as much of this petroleum in the source beds than in the reservoirs. The high concentration of hydrocarbons and organic matter in rocks such as the Woodford, Duvernay and Nordegg Shales does not automatically make

240

J. M. H U N T

them good source rocks. It is possible that the organic content of this type of sediment is so high that it tends to act as a blotter, that is, it adsorbs hydrocarbons instead of releasing them to the reservoirs. The fact that some rocks such as the Mission Canyon limestones have a very low hydrocarbon content does not necessarily mean that they have released a considerable amount of hydrocarbons to reservoirs. The quantities of hydrocarbons that were originally present or have been gathered from any of these sediments is not known. Some estimates could be made by adding up the hydrocarbons in both reservoir and non-reservoir rocks of an entire sedimentary basin, but this figure would not include losses over geologic time. It is interesting to note that most of the limestones and dolomites have hydrocarbon contents comparable to those of the shales even though the organic contents are lower by a factor of 10. This emphasizes the aforementioned importance of hydrocarbon analyses. The low organic content of carbonates compared to shales in Table VII agrees with Ronov's data in Table VI. Recent carbonate sediments, however, have organic contents very similar to those of Recent clays (Table VIII). GEHMAN (1962) suggested that most carbonates lose organic matter faster than shales due to repeated exposure to meteoric waters. An alternative hypothesis by E. T. Degens (personal communication, 1964) is that the carbonates contain primarily proteinaceous organic matter which is hydrolyzed during recrystallization, whereas the clays contain primarily humic and lignitic organic matter which survives the period of compaction and diagenesis. This is summarized in Fig. 1 and 2. If a large part of the organic matter is lost in carbonate sediments early in their diagenesis, it still does not explain why the remaining organic matter is such an efficient generator of hydrocarbons. The ratio of hydrocarbons to organic matter as shown in Table VIII is far higher in ancient carbonates than in ancient shales. Unfortunately, the proportion of hydrocarbons lost from these two types of rocks is TABLE VIII DISTRIBUTION OF HYDROCARBONS AND ASSOCIATED ORGANIC MATTER IN RECENT AND ANCIENT SEDIMENTS

(After HUNT, 1961) Sediments

fiydrocarbons (p.p.m.)

clays (Recent)2 clays (ancient)2 carbonates (Recent)l carbonates (ancient)2 1 2

Gulf of Batabano, Cuba. Average of samples from several areas.

50 300 40 340

Organic matter (weight %) 1.5

2.0 1.7

0.2

'

24 1

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

[7 Amino

compounds

Carbohydrotes Organic solvent extract Organic residue( humicl

Ancient shole (mean total organic matter 1

-Ancient limestone (mean total organic matter) Shell Carbonate (Mylilus Cali fornianusl

Limestone (Florida Bay)

Clay (Son Diego Tmughl

Fig.1. Organic maaer content of Recent marine sediments. (After E.T. Degens, personal communication, 1964.) WEIGHT PERCENT IN CLAYS

CONSTITUENTS

WEIGHT PERCENT IN CARBONATES

85

Humus and lignin

5

10

Proteins Sugars and lipids

90

=\>y.dorv!si Compaction

Only 5-10% 6;ganic

of proteins\Recrystallization

matter lost

About 75%organic matter lost

Fig.2. Loss of organic matter in sediments.

not known. As previously mentioned, it may be that most of the hydrocarbons generated in carbonates are trapped in them by early lithification, whereas those in shales represent a remnant of a much greater amount that was generated and partially lost. One of the most detailed studies of the distribution of hydrocarbons in the source-reservoir facies of a geological section was made by D. R. BAKER(1962). He found a wide Yariation between the hydrocarbon and organic carbon contents of sediments of different lithologies from the Cherokee group of Kansas and Oklahoma. His data for the principal lithologies are summarized in Table IX. The range in hydrocarbon content from these different lithologies, which are in very close stratigraphic proximity, is nearly as large as for samples from all over the world as shown in Table VII. All of the lithologies presented in Table IX could have contributed some hydrocarbons to the Cherokee reservoirs. The most probable sources would be the limestones and gray shales. The underclays and greenish-gray shales have too

242

J. M. HUNT

TABLE IX MEAN ORGANIC COMPOSITION OF PRINCIPAL ROCK TYPES OF CHEROKEE GROUP OF KANSAS AND OKLAHOMA

(After D. R. BAKER,1962) Rock type

underclay and related rocks greenish-grayshales and related rocks limestone gray shale black phosphatic shale

Number of samples

Hydrocarbons (p.p.m.)

Organic carbons Hydrocarbons (weight %) organic c

9

19

0.34

1.06

43 11 31 19

31 91 129 2,920

0.31 0.19 1.52 7.94

1.26 4.12 0.92 3.88

*

10-2

low a hydrocarbon content to be effective contributors, whereas the phosphatic shale is so rich in hydrocarbons that it might not release them. Baker’s data verify the results obtained by other investigators previously mentioned by showing a very high ratio of hydrocarbons to organic carbon in carbonates. In discussing his results, Baker mentioned the problem of differentiating hydrocarbons which have migrated vertically into a presumed source bed from those which are indigenous. This is a knotty problem which clouds any interpretation of hydrocarbon distribution in sediments. Most comparisons of crude oil in reservoirs, however, show that there are chemical similarities over several miles horizontally within a formation, but marked differences can be observed in only a few hundred feet vertically. The data of BASS(1963) are typical in showing the composition of crude oil in the Rangely, Ashley Valley and Elk Springs pools in the Weber sandstone to be similar even though they span a horizontal distance of 50 miles. On the other hand, the oils in the Weber, Shinarump and Mancos Sands are entirely different even though they span a vertical distance of only 4,000 ft. (less than 1 mile). This suggests that the migration of most crude oils occurs within neighboring stratigraphic units and does not span the entire vertical section of the basin. NERUCHEV (1962) also has geochemical data, to be shown later, which indicate that most hydrocarbons in the source beds are indigenous.

GEOCHEMICAL TECHNIQUES FOR RECOGNIZING CARBONATE SOURCE ROCKS

The studies reported above have provided much valuable information on how hydrocarbons are distributed in sedimentary basins relative to oil and gas accumulations. Many petroleum companies have also developed empirical methods of

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

243

source-rock identification which are based partly on experience and partly on faith. The first of these empirical methods was developed by PHILIPPI (1956) and associates of the Shell Oil Company. They considered fine-grained sediments with indigenous oils to be oil-source beds, the source-rock quality being defined as the amount of hydrocarbons present per unit weight of dry rock. Rocks with less than 50 parts of indigenous hydrocarbons per million parts ofdry sediment were considered very poor sources, whereas those with over 5,000p.p.m. were considered excellent sources. The LaLuna Limestone of western Venezuela was regarded as an important oil source by this method. The hypothesis on which this technique is based is simply that if a finegrained sediment contains indigenous hydrocarbons, it means that the sediment was capable of generating hydrocarbons and, therefore, is a source rock. One cannot really define the sediment as an oil source, however, unless oil from it has accumulated in commercial quantities. This requires not only generation but also release of the hydrocarbons and their accumulation in a suitable porous trap. Assuming that the hydrocarbons extracted by the Shell technique are indigenous, the method does fulfill the first requirement of a source rock but not the others. In effect, it gives a picture of the distribution of hydrocarbons in a sedimentary basin, and one must assume that the sediments with highest concentration of hydrocarbons will be associated with reservoirs containing the highest amount of oil. This is probably true for rocks with intermediate-range hydrocarbon contents, but it may not be true for rocks with very high hydrocarbon contents. As previously mentioned, if the rocks are oil wet, they would tend to adsorb the oil instead of releasing it. Another system for identifying source rocks has been reported by BRAY and EVANS (1961). They pointed out that the normal paraffins of Recent sediments, which eventually become part of crude oil, have predominantly odd-numbered chain lengths. The ratio of the amounts of odd to even chain lengths of hydrocarbons is 3-5/1. The reason for this was first discovered by CHIBNALL and PIPER (1934). They found that insect and plant waxes contain primarily the odd-numbered paraffin chain lengths. As these waxes from living organisms find their way into the sediments they would maintain this ratio. In contrast, it was found by Bray and Evans that the normal paraffins in crude oil contain practically equal quantities of odd- and evenhumbered chain lengths of hydrocarbons. The ancient sediments that might be considered as possible sources of the crude oils contained normal paraffins that have a greater preference for the odd chain lengths than the crude oil accumulations. This is generally less pronounced for the hydrocarbons in Recent sediments. These results are summarized in Table x. Bray and Evans reasoned that the initial difference in odd and even chain lengths of paraffins in living organisms and in Recent sediments was gradually reduced as the hydrocarbons that were generated in the sediments were added to the original hydrocarbons from the living organisms. Generated hydrocarbons would have equal amounts of odd

244

J. M. HUNT

TABLE X RATIO OF ODD- TO EVEN-NUMBERED I2-PARAFFINS IN SEDIMENTS AND CRUDE OILS

Source

Ratio of odd- to even-numbered n-parafins chain length

Recent sediments ancient sediments crude oils

2.5-5.5 0.9-2.4 0.9-1.2

and even chain lengths. Consequently, if enough of these were formed in comparison with the amount originally present, they would tend to obscure the odd chainlength preference observed in hydrocarbons from Recent sediments. Bray and Evans concluded that a sediment could be considered a source rock if it generated enough hydrocarbons to reduce the odd-even carbon ratio to 1.20 or less.'This is about the maximum value observed in crude oils. By this technique, both the Canyon Limestone of Texas and the Heath Limestone of Montana could be defined as source rocks because their odd-even ratios averaged 1 .O and 1.1, respectively. Of course, any of these source-rock techniques require examination of several samples within a formation, because a formation may not be uniform in its capability of generating hydrocarbons. KHALIFEH and LOUIS(1961) developed an oxidation method for determining source rocks. Briefly, their method consists of measuring the reducing power of the insoluble organic matter in the rock by adding a strong oxidizing agent such as potassium permanganate. The ratio of reducing power to total organic carbon is then plotted against the weight percent carbon remaining after oxidation. This indicates the state of reduction at various stages in the oxidation process. Khalifeh and Louis obtained three types of curves: (1) A rising curve, indicating that the more resistant organic matter consumes more oxygen and, therefore, is more reduced. This is characteristic of a good source rock. (2) A descending curve, indicating that the more resistant organic material consumes very little oxygen, that is, it has already been oxidized to some extent. This is characteristic of a poor source rock, or more continental-type organic matter. (3) In some instances, a straight line is obtained indicating that the organic matter is similar to that found in Recent muds, that is, it is in a state .of evolution, or still in the process of being reduced. By this technique, the LaLuna Limestone of Venezuela appears to be a good source rock and the Kimmeridgien limestone of France appears to have not yet generated any oil. VEBERand GORSKAYA (1963) studied the chemical composition of dispersed

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

245

bitumens as a means of recognizing source rocks. They cited the bituminous limestones of Carboniferous age in the Donets Basin as an example of carbonate source rock. They found that the dispersed bitumen in the limestones is a true petroleum, and, according to Veber, it was clearly indigenous. In one section of the Viscan Limestone, the asphalt found in a fracture was generally similar in composition to the dispersed bitumen in the limestone matrix. Any method for distinguishing migrating (allochthonous) hydrocarbons from native (autochthonous) hydrocarbons would be a method of recognizing source rocks. The presence of large quantities of migrating hydrocarbons would imply good source characteristics. USPENSKIY et al. (1958) first proposed that changes in the degree of bituminosity (percentage of hydrocarbons) in the total organic matter could be used to recognize traces of oil which migrated. The idea is that if oil is migrating, being redistributed within the mother rock, there will be sections of high concentrations of hydrocarbons which will stand out over and above the levels due to indigenous hydrocarbons. These would be considered migrated hydrocarbons. VASSOEVICH (1958) defined this more precisely by showing that the percentage of hydrocarbons in the total organic matter increased as the content of organic matter decreased. NERUCHEV (1962) demonstrated these concepts by logarithmically plotting the percent of soluble bitumens in total carbon against the total organic carbon content as shown in Fig.3. The line in this figure separates the anomalously high values of soluble bitumens from the background values. Points above this line represent migrated bitumens, whereas those below the line represent native bitumens. It can be seen that the percent of native bitumens increases with decreasing organic carbon. Vassoevich, who edited Neruchev’s book, pointed out that each different type of rock would have its autochthonous hydrocarbons on a different part of the diagram. The line in Fig.3 would shift with lithology. For example, carbonate rocks are known to have high native bitumen content in their organic matter, so that the line separating migrated bitumens would be higher than that for clays. Unfortunately, Neruchev does not state just how he decides where to draw the line. Neruchev also distinguished native and migrated bitumens by plotting frequency distribution curves of the bitumen content of samples from individual formations. Anomalous values believed to be caused by migrating bitumens stand out very clearly on these graphs. Generally the native bitumens represent more than 75 % of the total. This is also evident in Fig.3. At the end of his book, Neruchev presented equations for calculating the quantities of native and migrated oils in a sediment. The calculations are based on the idea that when a source rock gives up oil, there is a reduction in the contents of carbon and hydrogen and a proportionate increase in the contents of oxygen, nitrogen and sulfur in the organic matter of the rock. Also, there is a decrease in the amounts of oily fraction and hydrocarbons in the rock. According to Neruchev, by determining the amounts of carbon, hydrogen, oxygen, nitrogen

246

J. M. HUNT

I

Mlgrated bitumens

i

.iT 50-

i

l

10

11

51

tumens

I

0

5

0

0 OO0

0.5

1

i I

I

I

0.1

0.1

0.5

Total organic carbon

(weight percent)

Fig.3. Relationship between the total organic carbon content and the ratio of soluble bitumens in 1962.) total carbon. (After NERUCHEV,

and sulfur in various fractions of the organic matter, one can calculate the quantity of oil that has migrated from oil-generating deposits and thereby estimate the amount of total undiscovered reserves in the basin under study. Although he recognized the difficulty in estimating the amount of oil lost due to the lack of reservoir cover, he still felt that this technique could be used in oil exploration.

CONCLUSIONS

Table XI attempts to summarize the various concepts relating to source rocks. It is recognized in any comparison of lithologies, such as carbonates and clays, that the entire spectrum of conditions may be present in both groups. The statements made are designed to highlight the more significant differences rather than describing a typical carbonate or shale source rock. Carbonate deposition in open shelf areas occurs in shallow, well-aerated waters. The slow rate of deposition allows adequate time for destruction of the fleshy material of marine organisms, leaving the organic matter, which is largely

247

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

proteinaceous, in the shells. Somewhat greater quantities of organic matter would be preserved in the less common evaporite basins. Clay particles, in contrast, come from the continents with adsorbed humic and lignitic organic matter, and are deposited in the deeper, rapidly subsiding parts of the basin. More organic matter is preserved due to the rapid deposition, but there is also more mineral matter. Thus, the percentage of organic matter in the sediment is about the same for clays and carbonates. Carbonates lose their water in the first few feet of burial and undergo early lithification and recrystalliTABLE XI COMPARISON OF CARBONATES AND SHALES AS SOURCE ROCKS OF PETROLEUM

environment of deposition: rate of deposition: source of organic matter: type of organic matter: compaction and lithification: process of hydrocarbon generation from organic matter: probable time of hydrocarbon generation: probable time of HC migration: probable mechanism of HC migration: proximity of reservoir porosity to source:

effectiveness of reservoir traps:

Limestones and dolomites

Clay shales

shallow, aerated on open shelf but reducing in evaporite basins slow primarily marine proteinaceous, some humic early loss of water, rapid lithification and recrystallization thermal

deep, often reducing rapid primarily terrestrial humic and lignitic slow and continuous loss of water catalytic and thermal

late

early and continuous

late, after lithification and fracturing of the rock and development of solution permeability in solution or as globules moving along fractures and solution paths very near; oolites and reefs; fracture complexes; frequently porosity is developed in or close to the source (solution and dolomitization) good, due to frequent proximity of impermeable anhydrite covers

early during major movement of fluids in solution with the expelled fluid variable; many thick source beds have no interbedded porous rocks

average, considerable amount of oil is lost through sands, silts and continental sediments

248

J. M. HUNT

zation. Clay sediments have a slow and continuous loss of water from 80 % porosity a t the surface to about 8 % at a depth of 10,000 ft. (HEDBERG,1936). Experimental laboratory results obtained at the Petroleum Engineering Department of the University of Southern California show that the remaining moisture content (percent dry basis), at an overburden pressure of 10,000 lb./sq.inch varies from 6-32 %, depending on the type of clay (G. V. Chilingar, personal communication, 1965). Due to the catalytic effect of clays, even in the presence of water, hydrocarbons can be generated quite early in this process and migrate within the first 500 ft. of sediment. Many of these hydrocarbons will be lost because of the lack of adequate rock cover; therefore, it is important that suitable reservoirs and traps form early enough to catch the hydrocarbons while the major fluid movement is still going on in the basin. At depths beyond 5,000 ft. hydrocarbons are probably still being generated, but, due to the great decrease in permeability .and the minor amount of fluid movement, the hydrocarbons would have difficulty inmigrating out of the shales. In carbonates, on the other hand, the early cementation and recrystallization to form a lithified rock would be accompanied by hydrolysis and solution of much of the organic matter and probably some of the initially deposited hydrocarbons. Later in its history, as the carbonate rock became buried deeper, hydrocarbons would be generated thermally from the remaining organic matter and would migrate along the solution or fracture zones. The solution zones could be formed by infiltrating meteoric waters, or by fluids moving up from the deeper parts of the basin. One advantage of carbonate source beds over shales is the frequent close proximity of porous reservoir beds. Studies of the hydrocarbon contents of source beds generally show them to be most effectively drained in the presence of interbedded porous sediments. In carbonates the source and reservoir rocks are frequently in juxtaposition. Reservoir porosity (oolite, solution and dolomite porosity) may be scattered capriciouslj throughout a carbonate rock, whereas in a shale bed the associated sand development is more clearly delineated. Many thick shale sections contain vast amounts of hydrocarbons which could have made oil pools had there been interbedded porous zones. Carbonates deposited in evaporite basins also have the advantage of impermeable anhydrite covers which retain the oil much better than do shales in typical sand-shale sequences.

ACKNOWLEDGEMENTS

The author is indebted to Dr. K. 0. Emery, Dr. F. Manheim and Dr.'E. T. Degens for reviewing the manuscript, and to Mrs. T. Perras for typing it. This work was partially supported by the National Science Foundation Grant No.1599 and Contract Nonr-2196(00) with the Office of Naval Research.

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

249

REFERENCES

.

ARABIAN-AMERICAN OIL COMPANY STAFF,1959. Abqaiq-Ghawar oil field, Saudi Arabia. Bull. Am. Assoc. Petrol. Geologists, 43: 434-454. BAKER,D. R., 1962. Organic geochemistry of Cherokee Group in southeastern Kansas and northeastern Oklahoma. Bull. Am. Assoc. Petrol. Geologists, 46: 1621-1 642. BAKER, .E. G., 1962. Distribution of hydrocarbons in petroleum. Bull. Am. Assoc. Petrol. Geologists, 46: 76-84. BAKER, N. E. and HANSON, F. R. S.; 1952. Geological conditions of oil occurrence in the Middle East fields. Bull. Am. Assoc. Petrol. Geologists, 36: 1885-1901. BALLIE, A. D., 1955. Devonian System of the Williston Basin. Bull. Am. Assoc. Petrol. Geologists, 39: 575429. BASS,N. W., 1963. Composition of crude oils in northwestern Colorado and northeastern Utah suggests local sources. Bull. Am. Assoc. Petrol. Geologists, 47: 2039-2064. J. G., B R O ~ N B., L. and HEPNER, L. S., 1963. Isolation and identification of isopreBENDORAITIS, noids in petroleum. World Petrol. Congr., Proc., 6th, Frankfurt, 1963, V(15). BERGMANN, W., 1949. Comparative biochemical studies on the lipids of marine invertebrates with special reference to the sterols. J. Marine Res. (Sears Found. Marine Res.), 8: 137-176. (Editor), Organic Geochemistry. B E R ~ ~ M AW., N N1963. , Geochemistry of lipids. In: I. A. BREGER Pergamon, Oxford, pp.503-535. BITTERLI, P., 1963. Aspects of the genesis of bituminous rock sequences. Geol. Mijnbouw, 42: 183-201. BLUMER, M. and OMAN,G. S., 1965. “Zamene”, isomeric Ci9 monoolefins from marine zooplankton, fishes, and mammals. Science, 148: 370-371. BLUMER, M. and THOMAS, D. W., 1965. Phytadienes in zooplankton. Science, 147: 111-1149. M., D. W., 1964. Pristane in the marine envirsnment. B~MER , MULLIN,M. M. and THOMAS, Helgolaender Wiss. Meeresuntersuch., 10: 187-201. BODUNOV-SKVORTSOV, E. I., 1958. Results of geochemical investigations in the southern part of eastern Siberia. Geol. Nefti, 2(1B): 51-56. BRAY,E. E. and EVANS, E. D., 1961. Distribution of n-paraffins as a clue to recognition of source beds. Geochim. Cosmochim. Actu, 22: 2-15. BROD,I. O., 1959. Diagnostic indications of the processes of formation of bitumens, petroleum and gas. Novosti Neft. Tekhn., Geol., 1959(9): 246-254. A. C. and PIPER,S. H., 1934. Metabolism of plant and animal waxes. Biochem. J., CHIBNALL, 28: 2009-2019. CHAYKOVSKAYA, E. V., 1960. The question of carbonate oil source beds in the Turukhansk and Noril’sk districts. Izv. Vysshikh Uchebn. Zavedenii, Neft i Gaz, 3: 19-25. DUNNINGTON, H. V., 1958. Generation, migration, accumulation and dissipation of oil in northern Iraq. In: L. G. WEEKS(Editor), Habitat of Oil. Am. Assoc. Petrol. Geologists, Tulsa, Okla., pp.1194-1251. DUNTON,M. L. and HUNT,J. M., 1962. Distribution of low molecular weight hydrocarbons in Recenfand ancient sediments. Bull. Am. Assoc. Petrol. Geologists, 46: 2246-2248. EMERY, K. 0. and HOGGAN,D., 1958. Gases in marine sediments. Bull. Am. Assoc. Petrol. Geologists, 42: 2 174-2 188. ERDMAN, J. G., MARLETT,E. M. and HANSON, W. E., 1958. The Occurrence and distribution of low molecular weight aromatic hydrocarbons in Recent and ancient carbonaceous sediments. Am. Chem. Soc., Div. Petrol. Chem., Preprints, 3: 639-649. FORSMAN, J. P. and HUNT,J. M., 1958. Insoluble organic matter (kerogen) in sedimentary rocks of marine origin. In: L. G. WEEKS(Editor), Habitat of Oil. Am. Assoc. Petrol. Geologists, Tulsa, Okla., pp.747-778. FROST, A. V., 1945. The role of clay in the formation of petroleum in the earth’s crust. Progr. Chem., 14: 501-509. GEHMAN JR, H. M., 1962. Organic matter in limestones. Geochim. Cosmochim. Acta, 26: 885-897. GERARDE, H. W. and GERARDE, D. F., 1961. The ubiquitous hydrocarbons. Assoc. Food Drug Officials U.S.,Quart. Bull., 25-26:l. GINSBURG, R. N., 1957. Early diagenesis and lithification of shallow-water carbonate sediments in

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south Florida. In: R. J. LE BLANCand J. G. BREEDING (Editors), Regional Aspects of Carbonate Deposition-Soc. Palaeontologists Mineralogists, Spec. Publ., 5 , pp.80-100. GORSKAYA, A. I., 1950. Investigations of the organic matter of Recent sediments. In: Symposium “Recent Analogs of Petroliferaus Facies”. Gostoptekhizdat, Moscow. HEDBERG, H. D., 1936. Gravitational compaction of clays and shales. Am. J. Sci., 31(184): 241287.

HOBSON, G. D., 1954. Some Fundamentals of Petroleum Geology. Oxford Univ. Press, London, 164 pp. HOLLMANN, R., 1962. Uber Subsolution und die “Knollenkalke” des Calcare Ammonitico Rorso Superiore im Monte Baldo (Malm; Norditalien). Neues Jahrb. Geol. Paliiontol., Monatsh., 4: 163-179.

HUNT,J. M., 1961. Distribution of hydrocarbons in sedimentary rocks. Geochim. Cosmochim. Acta, 22: 3 7 4 9 . HUNT,J. M., 1962. Geochemical data on organic matter in sediments. In: Intern. Sci. Congr. Geochem., Microbiol. Petrol. Chem., 3rd, Budapest, 1962, Rept., I : 393412. HUNT,J. M. and JAMIESON, G. W., 1956. Oil and organic matter in source rocks of petroleum. Bull. Am. Assoc. Petrol. Geologists, 40: 477488. JURG,J. W. and EISMA,E., 1964. Petroleum hydrocarbons: generation from fatty acid. Science, 1444(3625): 1451-1452.

KHALIFEH, Y . et LOUIS,M., 1961. Etude de la matiere organique dans les roches skdimentaires. Geochim. Cosmochim. Acta, 22: 50-57. G. M. and RODRIGUEZ-ERASO, G., 1956. Habitat of some oil. Bull. Am. Assoc. Petrol. KNEBEL, Geologists, 40: 547-560. KREJCI-GRAF, K., 1963. Origin of oil. Geophys. Prospecting, 1 1 : 244-275. LINDBLOOM, G. P. and LUPTON,M. D., 1961. Microbiological aspects of organic geochemistry. Develop. lnd. Microbiol., 2: 9-22. MAIR,B. J. and MARTINEZ-PICO, J. L., 1962. Compostion of the trinuclear aromatic portion of the heavy gas-oil and light lubricating distillate. Proc. Am. Petrol. Inst. Sect. I , 42: 173. MCAULIFFE, C., 1964. Solubility in water of paraffin, cycloparaffin, olefin, acetylene, cyclo-olefin, and aromatic hydrocarbons. In preparation. MEINSCHEIN, W. G., 1961. Significance of hydrocarbons in sediments and petroleum. Geochim. Cosmochim. Acta, 22: 58-64. MILLER, J. B., EDWARDS, K. L., WOLCOTT, P. P., ANISGARD, H. W., MARTIN, R. and ANDEREGG, H., 1958. Habitat of oil in the Macaraibo Basin, Venezuela. In: L. G. WEEKS(Editor), Habitat of’ Oil. Am. Assoc. Petrol. Geologists, Tulsa, Okla., pp.601-640. NERUCHEV. S. G., 1962. Oilgenerating Suites and the Migration of Oil. Goskhimhizdat, Leningrad. OAKWOOD, T. S.,SHRIVER, D. S., FALL,H. H., MCALEER, W. J. and WUNZ,P. R., 1952. Optically active substances in petroleum. J. Ind. Eng. Chem., 44: 2568. OWEN,E. W., 1964. Petroleum in carbonate rocks. Bull. Am. Assoc.Petro1. Geologists, 48: 17271730.

PHILIPPI,G. T., 1956. Identification of oilsource beds by chemical means. Intern. Geol. Congr., ZOth, Mexico, 1956, Rept., pp.25-38. PRATT,W. E., 1942. Oil in the Earth. Univ. of Kansas Press, Lawrence, Kansas, 105 pp. RONOV,A. B., 1958. Organic carbon in sedimentary rocks. Geochemistry, 5 : 510-536. SILVERMAN, S. R., 1962. Carbon isotope geochemistry of petroleum and other natural organic materials. In: Intern. Sci. Congr. Geochem., Microbiol. Petrol. Chem., 3rd, Budapest, 1962, Rept., I : 328-341. SMITHJR., P. V., 1954. Studies on origin of petroleum: occurrence of hydrocarbons in Recent sediments. Bull. Am. Assoc. Petrol. Geologists, 38: 377404. SOKOLOV, V. A., 1957. Possibilities of formation and migration of oil in young sedimentary deposits. In: Proc. Lvov Conf, 1957. Gostoptekhizdat, Moscow, pp.59-63. TREIBS, A., 1934. Chlorophyll and hemin derivate in bitumens, rocks, oil, waxes and asphalts. Ann. Chem., 510: 42-62. USPENSKIY, V. A. and CHERNYSHEVA, A. S., 1951. Material composition of organic material from the Lower Silurian limestones in the region of the town of Chudovo. Tr. Vses. Nauchn. Issled. Geologorazvcd. Neft. Inst., 57.

THE ORIGIN OF PETROLEUM IN CARBONATE ROCKS

25 1

USPENSKIY, V. A., CHERNYSHEVA, A. S. and MANDRYKINA, Yu. A., 1949. About dispersed form of hydrocarbon Occurrence in different sedimentary rocks. Izv. Akad. Nauk S.S.S.R., Ser. Geol., 5 : 83. F. B., CHERNYSHEVA, A. S. and SENNIKOVA, V. N., 1958. On the USPENSKIY, V. A., INDENBOM, development of a genetic classification of dispersed organic matter. In: N. B. VASSOEVICH (Editor), Questions of Formation of Petroleum (Symposium)-Tr. Vses. Nauchn. Issled. Geologorazved. Neft. Inst., 128: 22 1-3 14. N. B., 1955. The Origin of Petroleum (Symposium). Gostoptekhizdat, Leningrad. VASSOEVICH, N. B., 1958. Formation of oil in terrigenous deposits (especially the ChokrakVASSOEVICH, Karagansk deposits of the Tersk anterior basin). In: N. B. VASSOEVICH(Editor), Questions of Formation of Petroleum (Symposium)-Tr. Vses. Nauchn. Issled. Geologorazved. Neft. Inst., 128: 9-220. VEBER,V. V. and GORSKAYA, A. I., 1963. Bitumen formation in carbonate facies of sediments. Sov. Geol., 8: 51-63. N. M., 1958. Gaseous hydrocarbons in Recent sediments. Geol. VEBER,V. V. and TURKELTAUB, Nefti, 2: 3944, English translation in Petrol. Geol., 2: 737-742. WEEKS,L.G. (Editor), 1958. Habitat of Oil. Am. Assoc. Petrol. Geologists, Tulsa, Okla., 1384 pp. (Editor), WEEKS,L. G., 1961. Origin, migration and occurrence of petroleum. In: G. R. MOODY Petroleum Exploration Handbook, p.24. WEISS,A., 1963. Organic derivates of mica-type layer silicates. Angew. Chem. Intern. Ed. Engl., 2: 143. J . M., 1959. Compaction of sediments. Bull. Am. Assoc. Petrol. Geologists, 43: 273-310. WELLER, E. C., 1945. A. P. I. Research Project 43B. Proc. Am. Petrol. Inst., Sect. IV, 25: WHITMORE, 100-101. ZOBELL,C. E., 1959. Introduction to marine microbiology. In: C. D. OPPENHEIMER (Editor), Marine Microbiology-New Zealand Oceanog. Inst., Mem., 3: 1-23.

Chapter 8

TECHNIQUES OF EXAMINING AND ANALYZING CARBONATE SKELETONS, MINERALS, AND ROCKS K. H.

WOLF^,

A. J . EASTON AND

s. WARNE

Department of Geology, The Australian National University, Canberra, A.C.T. (Australia) British Museum, London (Great Britain) Newcastle University, Newcastle, N.S. W . (Australia)

SUMMARY

The increasing emphasis on detailed study of the petrology of carbonate rocks has led to the adoption of a multitude of techniques that are described in a series of widely scattered publications. A selection of these techniques, of proven value in specific studies, has been brought together in this chapter in the hope that they will contribute to carbonate studies in general. In many cases, refinements and an increase in reliability of a particular technique will rest on a simultaneous use of associated methods and modifications to suit specific cases. The interpretation of the analytical results must be based on sound genetic concepts, which in some instances also require new approaches as discussed in other chapters in this book. INTRODUCTION

The impetus given to carbonate sediment research in the past few years has led to the application of numerous techniques, some old and others rather new. They range from simple quick field tests to highly specialized, time-consuming, and elaborate instrument-requiring approaches. The existence of a large variety of techniques necessitates a rather superficial treatment of a number of them in this chapter. In some cases only a short discussion and a few pertinent references are given, but for the more important procedures details of both methods and results are outlined. In no case, however, is it possible to treat the methods adequately enough to make the reader independent of the original publications. Fig.1 gives a general scheme that includes most of the usual methods employed in carbonate investigations. Owing to limitations of space there can be no complete coverage of the literature, and some omissions of pertinent references are unavoidable. Much credit is due to the various research workers from whose publications much of the information has been extracted. Present address: Department of Geology, Oregon State University, Corvallis, Ore. (U.S.A.).

254

K . H. WOLF, A. J. EASTON AND S. WARNE

Fig.1. Flow chart of examining carbonate sediments. (Modified after SHORT, 1962, by permission of Am. Assoc. Petrol. Geologists, Tulsa, Okla.)

FIELD STUDIES OF CARBONATE SEDIMENTS

In most geological studies, field work and collecting of samples form the basis for more precise investigations in the laboratory. Therefore, the importance of obtaining as exact and detailed information as circumstances permit during field work, or on the well site, cannot be too overemphasized. In large-scale regional reconnaissance work one usually is not concerned with the precise petrographic make-up of sediments. Just as it has become routine to divide terrigenous sediments into arkose, greywacke, and so forth, an attempt should be made to give as detailed a description of carbonate rocks as the particular conditions allow. The carbonates will reveal many textures, and structures when etched with dilute (1 :lo) HCl acid and then wetted with water and examined with a hand lens. At least the grain size and the presence of dolomite and terrigenous impurities can be determined. In addition, the rock can be described as calcilutite (= micrite), calcisiltite, calcarenite, calcirudite, dololutite, dolarenite

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

255

or dolorudite; or where crystalline, as microsparite, sparite or dolosparite (see CHILINGAR et al., 1966, for an outline in describing carbonates both descriptively and genetically). For fine sediments, thin-section studies are absolutely necessary to check field interpretations. In the coarser rocks the percentage of grains, matrix, and sparite cement is also determinable by hand lens and many of the fossil types can be recognized. In particular, if a binocular microscope is available, e.g., on the well site or in the base camp, descriptive classification of the specimens is possible. This facilitates the collecting of samples for detailed thin-section examination that may permit a precise genetic classification. For example, calcareous rocks thought to be lithographic or micritic limestones, and described as unfossiliferous and massive when examined with a binocular microscope, have been shown in thin-section studies to be composed of blue-green algal filaments, cells, etc. (WOLF,1963a, 1965a; CHILINGAR et al., 1967). Some of the Algae are useful in dating such limestones (JOHNSON, 1964). Thus, in the case of apparently unfossiliferous, massive micritic limestones thin-section studies are most pertinent for a precise paleontological and petrographic interpretation. If paleontological studies are to be made predominantly on one particular phylum, e.g., corals, brachiopods, stromatoporoids or Bryozoa, a quick check on the associated “micrite” matrix components may assist paleoecological and environmental reconstructions. In addition, if the micrite proves to be of algal origin, it may be possible to observe symbiotic relations between the organisms. In strongly folded areas, it is useful to examine hand specimens for geopetal (top-and-bottom) criteria, which help in structural and stratigraphic reconstructions. For example, large brachiopods or primary reef cavities may be partly filled with sediments at the bottom and have an upper sparite growth, thus providing useful top-and-bottom criteria where limestones are vertical or overturned. For detailed studies on textures and structures, it is important to collect oriented hand specimens in order to understand the diagenesis and paleoenvironments; qnd it is necessary to investigate internal sediments, replacement patterns of hematite and dolomite, orientation of stromatactis, and so forth. In studying terrigenous rocks it is desirable to test for carbonate components. The carbonate may be present either as cement, or as carbonate detritals, or both. The importance of this distinction has already been stressed (WOLFand CONOLLY, 1965). The foregoing indicates that in spite of limitations, a field geologist should endeavor to collect all possible information from HC1-etched and water-wetted hand specimens to assist in stratigraphic work and to facilitate the selection of samples for subsequent laboratory studies. In remote areas where field camps may be set up for lengthy periods, it is advisable to have available binocular microscopes, diluted hydrochloric acid, staining material, and other equipment for more detailed examinations. More precise analyses may help in solving stratigraphic problems, in particular where a number of similar-looking carbonate formations outcrop.

256

K. H. WOLF, A. J. EASTON AND S. WARNE

ACID-ETCHING OF CARBONATE SEDIMENTS

Even in reconnaissance studies, it is desirable to carry out acid-etching as pointed out above. The acid-etched surface reveals textural and structural features and assists in the identification of dolomite. Etching is also used ( I ) as a preliminary step to staining; (2) in the preparation of peels; (3) for electron-microscope studies; ( 4 ) in the determination of percentages of mixtures of calcite and dolomite using, for example, comparative charts (TERRYand CHILINGAR, 1955); and (5) in extreme cases of etching, this procedure grades into the separation of insolubles by acid-digestion (to be described below). Etching is employed on relatively smooth broken surfaces, on polished surfaces, and on drilling chips. Depending on the information required, etching may be the only method applied, but for accurate studies it has to be supplemented by thin-section, staining, chemical, and other techniques. Carbonates composed of particles less than 0.5 mm in diameter require thin-section studies. In general, only calcitic, dolomitic and the non-carbonate materials are identified in routine work. The examination of well cuttings will not allow a very precise determination of percentages, and it is sufficient to subdivide them into four lithologic groups. The following procedure is recommended (Low, 1958). Use chips about 1 /4inch in diameter and 1/8 inch thick and immerse them in cold dilute HCI (I :7-10). Observe reactions under the microscope, in particular, if effervescence is slow (clean microscope afterwards to prevent damage by fumes). In straightforward cases the reaction will be approximately as follows. Limestone: violent effervescence; frothy audible reaction; specimen bobs about and tends to float to the surface. Dolomitic limestone: brisk, quiet effervescence; specimen skids about on the bottom of the container, rises slightly off bottom; there is a continuous flow of COZ beads through the acid. Calcitic dolomite: mild emission of COZ beads; specimen may vibrate, but tends to remain in one place. Dolomite: no effervescence; no immediate reaction; slow formation of COz beads on the surface of the rock; reaction slowly accelerates until a thin stream of fine beads rises to the surface. A number of factors will modify these reactions, e.g., presence of noncarbonate constituents such as clay, anhydrite, and bituminous material, and may drastically reduce the rate of effervescence of calcitic rocks. The rate of reaction is also dependent on the size of the chips, presence of adhering powdered carbonate material, film of water adhering to the surface or present in pores, degree of porosity and permeability, and other factors. With some experience, however, the modifying conditions are relatively easy to establish. Argillaceous limestone 0.r marl, for example, will effervesce fast at the beginning, but the reaction will progressively slow down. If a rock chip is crushed with the blunt end of a pair of tweezers

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

257

or a probe, a rejuvenation of the acid reaction will occur. On the other hand, dolomite will react very slowly at first and reaction will gradually become more vigorous especially if the acid is heated. Very porous and permeable dolomite cuttings may react with acid in a manner rather similar to limestone or argillaceous limestone because of the larger surface area available to the acid and the greater buoyancy of the dolomite. IRELAND (1950) mentioned the advantage of examining “curved surface sections” of carbonate chips digested in acid. Whenever polishing equipment is available, thecarbonatespecimens should be cut, polished and etched with dilute hydrochloric, acetic, or other acids, or mixtures thereof, before binocular-microscope examination is undertaken. (Note: aragonite may invert to calcite if too energetically ground.) The size of the samples depends, of course, upon the material available and the information desired. LAMAR (1950) and IVES(1955) used specimens approximately 6 inches long, 2 inches wide and 4-3 inch thick. WOLF(1963a) used slabs up to 10 x 10 inches and larger in the study of stromatactis, surge-channel and algal colonial structures. Large drilling chips can be polished quite simply (without a lap) on abrasive paper, for instance, before acid etching. After polishing and cleaning thoroughly to remove all abrasive, the specimen to be etched is placed in a dish with the polished surface up. Modelling clay is useful to hold the specimen in position. The polished surface should be horizontal, for an inclined surface may be channeled by rising streams of bubbles, and the grooves may be confused with genuine sedimentary features. The acids employed in etching carbonates as recommended by LAMAR (1950) are: 23 ml C.P. glacial acetic acid in 100 ml water, or 8 ml concentrated HCI acid in 100 ml water. The etching times required vary and experiments are necessary until the best result for the particular rock is obtained. Lamar suggested 20 min etching with acetic acid and 5 min in hydrochloric acid for limestones, but shorter times may suffice. Dolomites require a longer reaction period, mild heating of the acid, or both. In general, a slow reaction is necessary to prevent the destruction of delicate features. To initiate a very slow reaction, the specimen may be covered with about inch of water, and sufficient acid is then added to commence mild effervescence. A deep etch is required in some cases, and about 0.5 mm of rock may be dissolved from the flat surface. After the specimen has been etched for a period of time as determined by trial-and-error, the acid may be siphoned off using an eye-dropper, and replaced by water. In this fashion the specimen will not be moved and none of the minute surface features, e.g., adhering insoluble specks, will be destroyed or removed. If the specimen is taken from the dish, it is preferable to immerse it twice or three times into a beaker of water instead of washing it under a stream of water. Under no circumstance should the sample be brushed. The surfaces of limestones etched with acetic or citric acid are occasionally covered with a fine powder that precipitates when the specimen is dried. To remove

++

258

K. H. WOLF, A. J. EASTON AND S. WARNE

the absorbed salt, the specimen is soaked for a few hours in several changes of water, or is rinsed quickly in a very dilute hydrochloric acid. The results of acid etching differ somewhat for acetic and hydrochloric acid (see excellent photos by LAMAR,1950). The latter develops a so-called “acid polish” due to the absence of strong differential solution; exceptions, however, have been noted. Coarsely crystalline calcite often appears “glassy”, i.e., it has the sparry appearance. Internal fossil structures and differences in grain size of calcite particles are usually well shown, and textures and structures are distinctly brought out. Dolomite, clay, silt, sand, chert, and other insoluble or less soluble components project above the etched surface. Acetic acid reacts less uniformly with the carbonates and usually produces a rough surface in contrast to the smooth HC1-etched surface. The action of acetic acid is considerably influenced by porosity, incipient fractures, grain contacts, size and relative purity of calcite grains, and so forth. Due to local micro-variations, the core and concentric rings of oolites exhibit differential etching, and so do fossils and calcite grains, for example. Because of the rough surface produced, insoluble material is not readily seen on the etched surface, especially if the carbonate is coarse-grained or coarsely crystalline. In general, both acids should be used in order to determine which gives the best result, especially if peels are to be prepared from the polished and etched surfaces. One should try different acids at various concentrations applied for selected periods of time. In a combination treatment a mixture of acetic and hydrochloric acids produces etched surfaces combining the characteristic effects of the individual two acids, namely, a semi-polished and subdued differentially‘etched surface. Dolomite etching is done best with dilute HCl than with acetic acid because of greater speed of reaction. In the case of pure dolomite, there is little difference between HCI and acetic acid etching results. LAMAR (1950) mentioned that the etching results with citric acid are similar to those of acetic acid, as are those of organic and carbonic acids. Oxalic, sulfuric, and other acids that produce relatively insoluble reaction products with calcite or dolomite, are usually undesirable for etching. PERCIVAL et al. (1963) have described a technique for cleaning and etching the surface of carbonate rocks with hydrogenion exchange resin which reveals details in texture and fossil morphology. It cannot be emphasized too much that in many cases etched polished carbonate specimens are not sufficient to give genetic connotations to the components present. To distinguish between faecal, bahamite and algal pellets, between autochthonous and allochthonous micrite, and between genuine open-space sparite cement and recrystallization sparite, to name only a few examples, thin-section studies are a prerequisite.

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

259

STAINING OF CARBONATE ROCKS A N D MINERALS

Staining has been used in carbonate petrography for the following six purposes. ( I ) Identification of minerals (e.g., FRIEDMAN, 1959; GRASENICK and GEYMEYER, 1962; WARNE, 1962). (2) Identification of isomorphous series in combination with refractiveindex determinations (e.g., WALGER, 1961). (3) Textural and structural studies of recent and ancient calcareous fossils, 1913; SABINS, 1962; EVAMY, 1963). carbonate rocks and soils (e.g., HEEGER, (4) Petrogenetic investigations, e.g., diagenesis, paragenesis (e.g., SABINS, 1962; EVAMY,1963). (5) Percentage determination (visual estimates or with point-counter). (6) For illustration purposes, because stained grains are more distinct from surrounding non-stained material in photomicrographs (e.g., SABINS, 1962; EVAMY, 1963). The staining procedures are applicable to 'the study of thin-sections with removed cover-slides (as long as heating is not required), smoothly broken handspecimens, drilling chips, polished surfaces, and uncemented loose carbonate material in the field, on well site, and in the laboratory. Certain methods have advantages over others, and it is often left to the individual investigator to select a technique most suitable for his purposes. In general, little skill and only a few utensils are necessary to obtain satisfactory results. Table I (WOLF,1963b) gives a number of staining reagents, procedures of application, and results. The more pertinent references have been given which should be consulted for details on staining of carbonates. A number of staining methods have not been included in the table, e.g., techniques using malachite green (HENBEST, 1931; HEDBERG, 1963) and methyl red (RAMSDEN,1954). One of the tests for dolomite is based on the fact that this mineral usually contains some iron in contrast to the calcite. Inasmuch as most carbonate minerals can contain traces of iron, this test may not be a safe one to employ in precise work. EVAMY (1963) proposed a scheme which enables the discrimination between iron-free and iron-containing calcite and dolomite on a semi-quantitative basis (Table 11). Results of staining are most reliable in the case of mineralogic end-members. As indicated in Fig.5, however, a number of isomorphous (solid-solution) replacements are possible and caution is in order in the interpretation of staining results. LEITMEIER and FEIGL(1 934) and GOTO(196 I , p.6 14) observed that minerals from different localities react differently to staining probably because of varying degrees of purity. Results also change with the optical orientation of the crystals. The reactions, however, occur between certain limits and are still useful for gross identifications. One of the major limitations of staining is its application to granular and

TABLE I OUTLINE OF STAINING METHODS FOR CARBONATE MINERALS

(After WOLF,196313) Chemicals

Preparation and method

Results

FeC13, (NH4)zS

RODGERS (1940): use 1 part of FeC13.6HzO and 10 parts of water and immerse specimen not more than 1 min, then wash specimen gently and dip it into (NH4)zS. STRAKHOV (1957) stated: in a solution of 1 0 4 5 % of FeC13 moisten the carbonate specimen 1-2 min, or put a drop of the solution on the specimen. Wash specimen with distilled water and then treat it with a solution of (NH&S for a few seconds. Wash again with caution. FRIEDMAN (1959): use 2.5% of a FeCh solution (=2.5 g in 97.5 ml of water); apply to the specimen for a few seconds.

Calcite = brown-black. Aragonite = brown-black. Dolomite = nearly colorlesspale green.

Remarks

The dolomite grains when smaller than

0.01 mm become nearly black. Ankerite,

magnesite, breunnerite, and siderite when below 0.01 mm in size and slightly green (STRAKHOV, 1957). The disadvantage of this stain is Ankerite = nearly colorless-pale its tendency to spread over adjacent green. grains; and it oxidizes, turning brown, Magnesite = colorless. Breunnerite = greenish. cracks and crumbles. Also, the film is (STRAKHOV, 1957.) easily washed off. If limonitic material is present Brucite = pale green. (Somewhat darker than dolomite; LEMBERG, in the rock, it will be changed to black 1888.) FeS by the (NH4)zS and will make Siderite = colorless. carbonate estimation difficult. If other black materials, e.g., carbonaceous components and magnetite, are present as impurities the stained carbonate is difficult to estimate. (1 888), According to LEMBERG dolomite and calcite cannot be distinguished if they are very fine grained. .~

AIzCls hematoxyline HZOZ

FAIRBANKS (1925): use 0.24 g of haematoxyline, 1.6 g of AlzCk and 24 ml of water. This solution is boiled and then cooled. A small amount of HZOZis then added to oxidize the haematoxyline to hematein. Immerse

Calcite = violet or purple. Aragonite = violet or purple. Dolomite = colorless. Ankerite = colorless. Magnesite = colorless. Breunnerite = colorless.

LEMBERG (1888): use 4 parts of &CIs, 6 parts of logwood and 60 parts of water, and boil it under constant stirring for 20-30 min. The dark violet mixture is filtered and used as staining fluid. STRAKHOV (1957), using the above

carbonate specimen in solution.

Siderite = colorless. Brucite = colorless.

method, diluted the solution with 1,OOO2,000 ml of water. He boiled the carbonate specimen for 5-10 min. On the other hand, Lemberg did not dilute the solution and did not boil the specimen. Different logwood contain different amounts of haematoxyline and hematein, and the stains formed according to Lemberg’s method are not uniform. Hence, Fairbanks’ preparation method is preferable. Disadvantages: (I) solution is unstable, (2) stain contracts and spalls off, (3) stain rubs off easily, and (4) due to spalling it is not useful if carbonates are very small. ~~

ordinary photographic paper

(1931): use 2 parts of HCI, HENBEST 88 parts of water and 10 parts of K3 Fe(CN)e solution and immerse the specimen for 30-70 sec. Better effects are obtained by using more dilute HCI and treating the specimen longer. (1963) in the study of HEDBERG cores used the same solution, but treated the samples for 5-60 min depending on composition. WARNE(1962): use solution of equal parts of 2 % HCI and 2 % K3 Fe(CN)6. Heating may be required according to Warne in the case of siderite and dolomite. The former reacts rapidly, whereas it may take 5 min for the dolomite to stain.

Dolomite = blue-dark blue if Fez+ is present (it is colorless if it lacks Fe).

(1957), According to STRAKHOV the above solution is best applied with ordinary photographic paper. This

STRAKHOV’S (1957) results with photographic paper: calcite and dolomite gave no

Fe-dolomite = dark blue. Ankerite = dark blue. Siderite = dark blue. Calcite and magnesite stain if they contain Fez+.

The solution is unstable and gives off HCN (poisonous). For relation between Fe content and rate of reaction and intensity of (1913) and EVAMY stain see HEEGER (1963) (see below and Table 11). Certain clays also stain relatively easysometimes easier than the carbonates. Warne reported that ankerite and ferroan dolomite stain well in cold solutions, whereas dolomite generally and siderite always require heating. On using cold and hot reagents, this test seems useful for the differentiation of ankerite and Fe-dolomite from siderite and possibly dolomite. The intensity of blue is related to the amount of Fez+ present.

s2 ?-

5

E;

2: ?-

2

U ?-

2:

F*

e

m

m

E!

E

2P * 0

>

6z ?-

;;I

m

TABLE I (continued) Chemicals

Preparation and method

Results

Remarks

ordinary photographic Paper (continued)

paper is washed in hyposulphite causing it to turn dark. Then it is soaked in 1 % 1 :20 HCI for a few seconds to a minute. The paper is pressed against the carbonate specimen for 1-10 min. Then the paper is soaked in a solution of KaFe(CN)g followed by washing in water and drying.

color impression. Ankerite = blue. Breunnerite = deep blue. Siderite = deep blue.

KaFe(CN)a alizarin red S HCI

For results see Table 11. EVAMY (1963): use the staining solution in combination with alizarin red S as shown in Table 11. The reagents can be employed independently or the alizarin red S and K3Fe(CN)e can be combined in a single solution. The solution is then acidified by 0.2 % HCI.

EVAMY’S (1963) method permits a rough estimation of the amounts of Fe content in calcite and dolomite and the recognition of ankerite.

Calcite = red-orange-red-brown. (I 892): required are LEMLIERG neutralsolutionsof 10”/.AgN03and20% K ~ C r 0 4Put . drops of former solution Aragonite = spotted red or unstained (see remarks). on the specimen, heat it to 60-70°C (others boil it), and maintain it for Dolomite = nearly colorless. 2-5 min. Then wash the sample care. Ankerite = nearly colorless. fully and treat the specimen with Magnesite = nearly colorless. K2CI-04 solution for a few seconds. Breunnerite = nearly colorless. Wash again and let it dry. FRIEDMAN (1959): immerse the Siderite = colorless. According to Friedman: specimen for 2-3 min and use a Magnesite = brown. saturated K2CI-04 solution. THUGETT (1910) and STRAKHOVGypsum = brown. Dolomite = colorless. (1957) suggest a 0.1 % AgN03 solution. According to LEMBERG

The rate of staining of the less reactive carbonates, e.g., dolomite, depends on the grain size. STRAKHOV (1957) found that large grains of dolomite remain unstained, whereas those smaller than 0.01 mm become brown. Aragonite from different localities reacts differently according to ( I 892). If the AgN03 LEMBERC solution is too strong (greater than 273, the reaction between aragonite and the solution is too vigorous and no stain adheres to the surface; hence, apparent unstained appearance. The reaction of aragonite is 1,800 times that of calcite

( I9 10). If a very weak AgN03 (I .7 % = ( 1892) and THUGETT strontianite, magnesite and dolomite react only very slowly (see aragonite stains red, witherite column to the left). slightly red, and strontianite remains unaffected.

0.1

~~

MnS04.7HzO AgzS04 NaOH (Feigl’s solution)

diphenylcarbazide alcohol NaOH or KOH

~

N)solution is used for 1 sec,

~~

In 100 ml of water dissolve 11.8 g of MnS04.7HzO. Add to the solution solid AgzSO4 and boil. After cooling, filter the insoluble material. Then add 1-2 drops of dilute NaOH solution, and filter off the precipitate after 1-2 h. Keep reagent in a brown bottle. Put specimen into solution (powder, for 3-5 min; sections, for 30-50 min). Instead of placing the specimen into the solution, it can be dabbed gently with some material soaked in the Feigl’s solution.

Aragonite = grey. Strontianite = grey. Witherite = grey. Calcite, dolomite, magnesite, ankerite, siderite, smithsonite, and cerussite need much longer time than the above three to stain.

A test-tube or some other container is filled with about 15 cm3 of alcohol and 1-2 g of diphenylcarbazide is dissolved by heating. Then add 3-5 mg of NaOH or KOH (25 %). Add the grain of carbonate to be examined and boil for 2-3 min. The solution is poured out and the specimen boiled with some water. The water is changed until it remains uncolored. FErGL (1958) recommended to place drops of hot solution on a spot plate before adding the rock. After 5 min the solution is pipetted out and

Magnesite = lilac. Breunnerite = rose. (STRAKHOV, 1957) = colorless (FEEL, 1958). Siderite = dark grey (STRAKHOV, 1957). All other carbonates remain unstained according to STRAKHOV (1957). According to FElGL (1958), magnesite becomes red-violet. When Mg is in dolomite

(THUGETT,1910). (I 892) gives staining LEMBERG procedures for some non-carbonate minerals as well.

RP 3

I

.

______

LEITMEIER and FEIGL (1934) give a table showing the reactions of numerous carbonates in time. Sequence of reaction is as follows: (I) aragonite, strontianite, witherite, (2) smithsonite; (3) cerussite, ankerite, (4) dolomite; (5) calcite; (6) siderite; (7)crystalline magnesite; and (8) pure gel magnesite. Minerals from different localities often react somewhat differently but always within certain limits.

z >

2

>

2 U

> z > r $ E r A

B

5> XI

< > c1

STRAKHOV (1 957) recommended a procedure for the preparation of stained thin-sections. Note slight apparent discrepancy between the results of STRAKHOV (1957) and F E E L (1958). The latter stated that magnesite can be distinguished from both dolomite and breunnerite by this test. The reaction does not take place “when the magnesium carbonate is in the form of dolomite which is usually regarded as a double carbonate CaMg(CO3). .regarded as the complex CaMg(C0a)z. The magnesium

E

0

z >

3

.

h)

Q\

w

h,

TABLE 1 (continued)

m

P

Chemicals

Preparation and method

Results

Remarks

diphenylcarbazide alcohol NaOH or KOH (continued)

replaced by hot water. The washing continues until the water remains clear.

combination (or in breunnerite). no color results. The Mg can then be detected by taking a fresh sample and igniting it on platinum. The resulting sample can be stained as described above. (See test using magneson.)

is thus a constituent of a complex anion, and therefore has lost its normal reactivity. . .” Breunnerite is isomorphous with dolomite and also gives no reaction for magnesium. If dolomite and breunnerite are ignited, the dolomitic linking is destroyed and Mg can be detected with diphenylcarbazide, in the resulting mixture of oxides. (See magneson test.)

The powder of the carbonate is boiled for 2-3 min. in a solution of 5 % of Cu(N03)~.Thenthe solution is decanted and the specimen washed in 1940; STRAKHOV, water (RODGERS,

Calcite = bright green. Aragonite = bright green. Dolomite = unstained or pale green. Ankerite = pale green. Magnesite = pale blue. Breunnerite = unstained. Siderite = unstained.

Large dolomite grains remain unstained, whereas those smaller than 0.01 mm become pale green. See recommended procedure using C~(N03)zPIUS NH40H.

The specimen is put for 5-6 h in a solution of 5 % Cu(N03)~.The solution is removed and the specimen treated for a few seconds with a solution of concentrated ammonia. (1 940) and RODGERS FRIEDMAN (1959) recommended a molar solution of Cu(NO3)z (= 188 of Cu(N03)z ,225 g of Cu(N03)z. 3Hz0 or 332 g of Cu(N0&.6HzO

Calcite = blue-green. Aragonite = blue-green. According to Ross (1935): Mn-rich calcite = unstained. Siderite = unstained. Ankerite = unstained. Rhodochrosite = unstained. Pure calcite = blue-green.

1Y57.)

to 1,OOO g of water) into which the carbonate specimen is immersed for 2.5-6 hours depending on intensity of stain desired, and then treated with NHIOH (without washing and before drying) for a few seconds. (See also Ross, 1935; and STRAKHOV, 1957.) The carbonate specimen is boiled for 5 4 min in a concentrated solution Of cO(N03)z. FRIEDMAN (1959): use 2 cm3 of 0.1 N Co(N03)~solution to which 0.2 g of the sample is added, boil and filter. LEITMEIER and FEIGL (1934, following Meigen): use a 5-10% Co(N03)~solution and boil specimen 1-5 min depending on grain size.

~~

eosin KOH

Calcite = unstained, or lilacrose, or faint blue. Aragonite = dark violet. Dolomite, ankerite, magnesite, breunnerite, and siderite remain unstained.

.~

~

Fill test tube half full with alcohol (about 15 ml) and dissolve 1-2 g of eosin by heating. Add about 3 mg of 25 % KOH. The carbonate specimen is placed into the solution and boiled for about 2 min. Then the solution is decanted and the specimen 1957). washed with water (STRAKHOV, (Eosin = red tetrabromofluorescein)

Coarsely crystalline calcite remains unstained. Microcrystalline calcite becomes lilac-rose. After boiling for 10 min, the calcite becomes light blue. LEITMEIER and FEEL(1934) stated that calcite stains grey, green, yellow, or blue, but never violet when boiled for some time. Some contradictions have been 1959.) reported. (See FRIEDMAN, Boiling time may be critical. Not useful for staining thinsections as boiling is required. (1934) LEITMEIER and FEIGL reported spreading of stain over adjacent grains.

Calcite = unstained. Aragonite = unstained. Dolomite = unstained. Ankerite = unstained. Magnesite = faint rose. Breunnerite = pale rose. Siderite = faint rose.+

TABLE I (continued) Chemicals

Preparation and method

Results

Remarks

magneson NaOH and HCI

WARNE(1962): prepare the reagent by using 0.5 g of magneson (= paranitrobenzene-azoresorcinal) added to 100 ml of 0.25 N (= 1 %) NaOH. The HCl-etched and washed specimen is covered with equal amounts of reagent and 30 % cold NaOH solution. MANN(1955): suggested to drop some dilute HCl on the specimen; and when all effervescence has ceased, a drop of the alkaline magneson solhtion is introduced into the earlier drop. (See a h 0 STRAKHOV, 1957.)

Magnesite = blue. Smithsonite = unstained or shows faint tint to blue after 5 min. Calcite may stain if immersed too long. Dolomite = unstained Breunnerite = unstained. According to MANN(1959, MgO is present if the drop turns blue in about 30 sec.

The stain is unstable and disappears rapidly. Dolomite and breunnerite do not stain in the alkaline solution because the Mg forms a complex ion and is not available for the reaction with the dye (FEIGL,1958, p.465). If dolomite is ignited in a platinum crucible, the dolomite linking is destroyed and MgO is formed. MgO reacts with the dye. If HCI acid is put on the dolomite prior to adding the alkaline magneson solution, the Mg is precipitated and allows the magneson to become attached to it and color it. This latter test does not show whether the Mg comes from a dolomite or magnesite, for example.

methylviolet (violet writing ink)

Two possible procedures are proposed by STRAKHOV(1957): (I) To an ordinary violet writing ink (methylviolet) add a small. amount of HCl, causing a change to green color. If one drop of that solution is put on calcite or dolomite, the acid is more rapidly neutralized by calcite than dolomite. (2) Oxidize the methylviolet with 5 % HCl until an intense blue color is obtained. Soak the carbonate specimen in the solution (or put a

m

(1) The spot on the calcite

5

turns immediately violet; on the dolomite the spot remains green for some time.

(2) Calcite = violet. Aragonite = violet. Dolomite = unstained or pale violet.

0 2:

The dolomite crystals less than 0.01 mm in size become pale violet.

layer of the solution on the specimen) and leave it there for 1.5-2 min. Apply carefully a blotting paper. alizarin red S 2 % HCI

alizarin red S 30% NaOH

alizarin red S 5 % NaOH

z 2

Dissolve 0.1 g of alizarin red S in 100 cm3 0.2 % cold HCl(0.2 % HCl = 2 cm3 of concentrated HCI plus 998 ml of water). The specimen to be tested is first etched in 8-10 % HCI (see WARNE,1962, p.34) and then covered with the cold alizarin red S solution and allowed to react for about 2-5 mill. SCHWARTZ (1929), FEIGL (1958), FRIEDMAN (1959), and WARNE(1962).

Calcite, aragonite, high-Mg calcite, and witherite = deep red. Ankerite, strontianite, Fe-dolomite, and cerussite = purple. Anhydrite, siderite, dolomite, rhodochrosite, magnesite, gypsum, and smithsonite = no color.

Use equal volumes of alizarin red S and 30 % NaOH solutions (30 % NaOH = 30 g of NaOH plus 70 ml of water). Add specimens to be tested and boil for 5 min. Alizarin red S solution is prepared by dissolving 0.2 g of the dye in 25 ml methanol, by heating if 1959). Replenish necessary (FRIEDMAN, any methanol lost by evaporation.

Calcite = no stain. High-Mg calcite = purple. Dolomite = purple. Magnesite = purple. Gypsum = purple. Anhydrite = no stain. Witherite = no stain. Siderite = dark brown-black. Rhodochrosite = purple. Smithsonite = purple. Aokerite = dark purple. Cerussite = dark red-brown. Strontianite = no stain.

Use equal volumes of alizarin red S and 5 % NaOH solution and boil therein for about 5 min. Etch specimen first in 10% HCI. (See WARNE, 1962, p.34; and FRIEDMAN, 1959.)

Dolomite = unstained or faint color. Rhodochrosite = unstained or faint color. Magnesite = purple. Gypsum = purple. Smithsonite = purple.

2; WARNE(1962) reported that no staining occurred when reagent was applied for 5 min. Prolonged staining produced slightly purplish surface on the dolomite. According to SCHWARTZ (1929) staining is successful with carbonates with grain-size of 0.5-1.5 mm. Below this size distinction becomes difficult due to spreading of the stain.

5 2

+ z U > z

EE

8 vl

F;

3

Etch the specimen first in 10% HCl (WARNE,1962, p.34). HENBEST (1931): use KOH instead of NaOH (1 part KOH to 119 parts of water in which the maximum amount of alizarin red S is dissolved). Alizarin red S at 26°C has a solubility of 7.6 % in water.

> w

*

0

>

ti2 2

vl

-

s

h,

TABLE I (continued) Preparaiion and method

Results

titan yellow 30% NaOH

Boil carbonate s w i m e n to be tested in solution of titan yellow and 30% NaOH (FRIEDMAN, 1959).

Calcite = unstained. Aragonite = unstained. Anhydrite = unstained. High-Mg calcite = orange-red. Dolomite = orange-red. Gypsum = orange-red. Magnesite = orangered.

titan yellow 5 % NaOH

Boil specimen in solution of titan yellow and 5 % NaOH (FRIEDMAN,

High-Mg calcite = orange-red. Gypsum = orange-red. Magnesite = orangered. Dolomite = unstained.

1959).

..

Hams’ hematoxylin

rhodizonic acid

---

Remarks

High-Mg calcite studied by Friedman

(1959) was very fine grained. Degree of

coloration of the high-Mg calcite apparently depends on the amount of Mg present (FRIEDMAN, 1959).

- -- -

Harris’ hematoxylin can be purchased commercially or can be. prepared as described by FRIEDMAN (1959). Solution is made up of 50 ml commercia1 grade Harris’hematoxylin and 3 ml 10% HCI. 3-10 min are required to stain specimen.

Calcite = purple. High-Mg calcite = purple. Aragonite = purple. Magnesite = no stain. Gypsum = no stain. Anhydrite = no stain or faintly orange. Dolomite = no stain.

The more frequently the solution i s used, the quicker the stain takes effect. A fresh solution will often require 9-10 min to stain, whereas a frequently used solution may need only 3 min or less (FRIEDMAN, 1959).

Dissolve 2 g of disodium rhodizonate in 100 ml of distilled water. The specimen to be tested is etched in dilute HCI and washed several times in distilled water. The specimen is then submerged in the reagent for 5 min (FEIGL,1958; WARNE,1962).

Witherite = orange-red. Calcite = no stain.

T h e spot test proposed (FEIGL,1958,

x T

x sl

Chemicals

3

&!.

? 2 m

% p.220) utilizing sodium rhodizonatc, can detcct strontium in very small quantities.

4

5

v1

I > a

z

benzidine

Dissolve 2 g of pure benzidine Rhodochrosite = blue stain in 100 ml of water which contains (almost immediately). 1 ml of 10 N HCI. The HC1-etched Dolomite = not stained. specimen is washed several times, after which the specimen is immersed in a dilute solution (1-3 %) of NaOH for about 1.5 min. Then it is covered with cold benzidine solution (WARNE.1962).

See FEEL(1958, pp. 175 and 416) for spot test using benzidine. (The production of benzidine has been discontinued by some companies because of the cancer risks involved in the preparation of the pure material.)

rn

x

$

2

$z

5U

270

K. H. WOLF, A. J. EASTON AND S. WARNE

crystalline carbonates of which the individual particles are larger than about 0.01 mm. STRAKHOV (1957) found that below this grain size some staining procedures lead to results that differ from those obtained on using coarser material. Some staining methods depend on the rate of solution of the carbonate in acid, e.g., difference between aragonite and calcite (FRIEDMAN, 1959), and between calcite and dolomite. In the latter case, very finely powdered dolomite forms C02 rapidly and, therefore, may be confused with calcite (HEEGER, 1913). A few of the staining reagents spread readily over neighboring particles and make identification and percentage determinations difficult. Hence, it may be necessary to modify the manner of application of the reagents. For example, gentle dabbing of the specimen with a cloth soaked in the reagent, or pressing the specimen against a reagent-wetted blotting paper may give satisfactory results. A similar approach may be required to prevent staining fluids from penetrating into openings in the case of porous carbonate rocks. As has been illustrated by FRIEDMAN (1 959) and WARNE (1962), a few of the staining techniques listed in Table I can be used to identify most of the major carbonate minerals by a progressive elimination scheme shown in Fig.2 and 3. The other methods are given for those who wish to experiment with different techniques and for the purpose of double-checking a mineral identification. Further research on the applicability of staining for semi-quantitative determinations of isomorphous minerals and minor element-containing carbonate minerals, possibly in combination with spot tests, may improve and expand the methods available at present.

I

Alizorln red S t3OXNoOH boll

ANHYORITE

HIGH-Mg CALCITE

SIDERITE

[ree=,

CALCITE

WITTHERITE

DOLOMITE RHOOOCHROSITE

ANKERITE STRONTNNITE CERUSSITE

MAGNESITE WITHSONITE

or

GYPSUM

Fig.2. Staining scheme for the identification of carbonate minerals employing alizarin red S; (After WARNE,1962b, by permission of the Journal of Sedimentary Petrology.) I = or faint stain.

m x

TABLE I1 STAINING METHOD OF CALCITE, DOLQMITE AND ANKERITE, CONSIDERING Fe-CONTENT

(After EVAMY, 1963) _

Staining reagents

Calcite

Compositions are given in weight percent. Critical solution strengths are underlined.

Fez+

__

Fez+

Fez+

Dolomite

Fez+

Fez+ MT+<'

Fez+

Mg2+'1 -

free.

poor

rich

free

calcite s. str.

ferroan calcite

ferroan calcite

dolomite s. str.

ferroan dolomite

ankerite

0.2 % hydrochloric acid _ ~ . ~ _ _ _ 0.2% alizarin.red S

red

red

red

not stained

not stained

not stained

0.2 % hydrochloric acid -~ 0.5-1 .O % potassium ferricyanide

not stained

light blue

dark blue

not stained

light blue

dark blue

0.2 % hydrochloric acid 0.2% alizarin red S 0.5-1 .O% potassium ferricyanide

red

mauve

purple

not stained

light blue

dark blue

~

gU 5

E

272

K. H. WOLF, A. J. EASTON AND S. WARNE

mrellow’l 30% Na?H + boic

ANHYDRITE Fei I’J solution

HIGH-Mg CALCITE

GYZ$JM

MAGNESITE

CALCITE

ARAGONITE

Fig.3. Staining scheme using titan yellow. (After FRIEDMAN, 1959, by permission of the Journal qf Sedimentary Petrology). I = see FRIEDMAN (1959) for other excellent stains; 2 = or faint stain (light orange); 3 = high-magnesiumcalcite used in this study was very fine grained. The behavior of coarse-grained high-magnesium calcite was not studied.

PEEL TECHNIQUES

Peel prints have been used to facilitate the examination of both well-lithified and unconsolidated carbonate and terrigenous sediments with or without additional staining. Peels may be useful also in the study of metamorphic and igneous rock fabrics as mentioned by BISSELL(1 957). It seems that peels have not been applied to the best advantage in structural analyses. As Bissell and HEEZEN and JOHNSON(1 962) pointed out, peels can be made even from outcrops. The following procedure is based essentially on that described by MCCRONE (1963) with minor alterations and additions. (I) Prepare a polished flat rock section; polish with fine abrasive on a flat glass plate in the final stage. Different grades of abrasive have been suggested ranging from 400-1,000. Abrasive 600 seems to give satisfactory results. (2) Etch the polished surface with dilute hydrochloric or acetic acid, or a mixture of the two, to obtain optimum results as suggested in the section on etching. Experiments soon will reveal the best combinations of acid types, strength and application time. McCrone suggested dilute (1 %) hydrochloric acid applied for 10 sec. This time may be too short, in particular in the case of dolomites, and the time may be prolonged accordingly. McCrone stated that dilute acetic acid precipitates “faint films of indefinite composition” which tend to cloud the peel-prints, and that this precipitate is difficult to remove without obliterating some of the fine details of the textures. It has been shown in the section on etching, however, that the precipitated salt (e.g., calcium chloride) can be easily dissolved

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

273

by immersing the specimen for a few hours in several changes of water or by a quick rinse in very dilute HCI (LAMAR,1950). BEALES(1960) suggested a “standard” of 5 % v/v hydrochloric or 5 % v/v acetic acid applied to limestones for I5 sec or 5 min, respectiveIy. The time should be changed according to needs. For immersion over-night, 0.5% acetic acid or very dilute HCI give good results. (3) After etching, wash the specimen with water and then with alcohol or acetone without touching and leaving “finger prints” on the etched surface. If acetic acid has been used, remove any precipitate as mentioned in 2 above (see also the section on etching). ( 4 ) Place the rock specimen, with polished surface up, horizontally into a tray, pan or dish filled with coarse sand. The latter will hold the specimen in place and absorb the spilled acetone. (5) Have ready a piece of single-matte commercial acetate film (0.005-inch thick) slightly larger than the polished rock surface. (D. W. LANE,1962, used film 0.002-0.003-inch thick.) (6) Wet the polished surface with acetone by pouring a small amount from the bottle without flooding the specimen. (For other peel solutions see BUEHLER, 1948; and BISSELL,1957.) (7) Hold the acetate film between thumb and forefinger so that it forms a U-shape. Apply the dull side of the film to the rock so that the base of the “U” is first to touch the acetone-wet surface near the center. By letting the film unroll onto the polished section, no bubbles will be trapped. Do not press the film against the rock to prevent smearing and breaking of delicate textural features. BEALES(1960) and others suggested to place the turned-over specimen on a smooth surface. An alternative method is to place the acetate film on a glass plate, adding a little acetone near the center of the film and lowering the specimen onto it. In any case, one should avoid sliding the specimen on the film. (8) Allow the film to dry for 15 min or longer. Then, starting at one corner, gently peel it from the rock. (9) Mount the peel between two pieces of lantern-slide glass and bind them with tape. The mounted peel can then be used in a photographic enlarger to make enlarged peel prints on high-contrast paper. Mounted peels can be used also as lantern slides for projection on a screen, or for direct examination under a microscope (MCCRONE, 1963). To obtain photomicrographs, HARBAUGH (1959) projected the “peels in a standard photographic enlarger onto high-contrast photographic printing paper, such as Kodabromide F-5. The enlarger lens aperture was stopped down to about f / l l to give sufficient depth of field to insure sharp focus. Negative peel prints produced in this way have proved more convenient to use than peels themselves because the prints provide several magnifications and several prints may be easily viewed and compared simultaneously.” Equally well this technique may be used

274

K. H. WOLF, A. J. EASTON AND S. WARNE

with thin-sections. To obtain positive prints, one may project onto a cut film or negative glass slide (e.g., quarter plate size) and then contact print. As the peel picks up minute specks of the rock surface, some peels accurately record color as well as the texture. In some cases it may be desirable to emphasize certain textures, minerals or fossils by staining before the peel is taken. BISSELL (1957) stated that it may be profitable to make stained peels of varying thickness, depth of color, and intensity of fabric. It is evident that minerals cannot be identified in peels by optical means. Euhedral minerals, however, are recognizable in some cases by their crystal habit. In one instance (WOLF,1963a), peels showed clear hexagonal features of minute authigenic quartz crystals in algal limestones, and cubic outlines of pyrite. A peel technique for unconsolidated sediments has been described by HEEZEN and JOHNSON(1961), which has to be applied soon after the sediments have been obtained and prior to dessication and shrinkage obliterates many features. Experiments with a number of glues and plastics indicate that polyvinyl emulsion is the best suited, in particular because it can be diluted with water to decrease its viscosity, and inasmuch as it dries clear. Depending on the type of sediments, different proportions of plastic and solvent are necessary. The advantages of peels are numerous: (I) little skill, time, equipment and expense is required in their preparation with easily available material; (2) they can be easily filed and projected onto a screen; (3) peels are easier to photograph than polished sections as transmitted light is utilized; (4) peels can be made under circumstances where equipment necessary for the preparation of thin sections is unavailable; (5) examination of peels helps in selecting critical areas that demand thin-section studies; and (6) peels can be made of very large polished sections, in contrast to the limited size of thin sections,.which makes them particularly advantageous in textural and structural studies.

SEPARATION OF INSOLUBLES

The reasons for separating non-carbonate and carbonate components include the following. (I) To determine the two- or three-dimensional distribution of the noncarbonate fraction in the carbonate rock, thus permitting the petrographic and petrologic examination of syngenetic and authigenetic as well as diagenetic mineral distribution. (2) To investigate the different minerals of the non-carbonate fraction (e.g., clays, organic matter, glauconite, heavy minerals, and so forth). (3) To investigate more easily the remaining carbonate fraction. One of the most difficult tasks is to achieve separation without causing compositional alterations of the so-called “insoluble” residue. Progress in some

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

275

fields of carbonate petrology may well depend on the development of new separation techniques. This is particularly the case in trace-element and isotope studies of the carbonate versus the non-carbonate constituents. Certain techniques have been proposed that allow separation of the “insolubles” with a minimum destruction and which were sufficiently satisfactory in the particular types of investigations. Acetic acid, for example, is thought to be useful in clay-mineral separation without destroying the mineral structure (as determined by X-ray diffraction analysis). Little published information, however, is available on the effects of the organic and other inorganic acids and ion-exchange resins on the trace elements. In general, the term “insoluble” residue is somewhat misleading as most substances are soluble, however small the solubility may be. A useful technique that has the advantage in that non-carbonate components can be observed in their original position and may be removed for further study has been mentioned by LEE(1958) and HEDBERG (1963). The procedure is given below. ( I ) Prepare a thin rock slice. Orientation depends on the information desired, of course. Usually sections vertical to the bedding are used. In three-dimensional investigations, however, sections parallel to the bedding are often required. (2) The rock slice is ground and polished smooth on the side to be mounted. (3) The slice is immersed in 20% acetic acid for approximately 5 min and subsequently thoroughly washed and dried. ( 4 ) The prepared side is mounted with a resin as mountant on a glass slide. Lakeside No.70C, for example, is useful, whereas Canada Balsam mounts are less successful. (5) The rock.slice is ground down to approximately 0.030 mm, and the final stage is done with the finest abrasive. (6) The whole section is then placed in 20% acetic acid and the carbonate completely dissolved away. The non-calcitic carbonates can be easily examined or removed for refractive-index determinations. Non-carbonate minerals can be examined by normal means after the surface has been moistened with water. If all carbonate minerals are to be removed, the above procedure is performed with dilute or concentrated hydrochloric acid. Etching prior to mounting has been done with acetic acid to produce differential etching. The “acid-polish”, or smooth surface produced by hydrochloric acid, is undesirable. The differentially attacked limestone surface permits the resin to penetrate into the slice when mounted. Thus, after complete digestion of the carbonate material, the texture of the original rock is preserved on the resin. This replica is best examined on a dry mount using reflected light or transmitted light and crossed nicols. Minute details, down to the size of calcisiltite, are observable in the replica. HEDBERG (1963) used a slightly modified version of Lee’s technique. In-

276

K. H.

WOLF, A.

J. EASTON AND S. WARNE

stead of etching the sample prior to mounting, the rock slice is highly polished as in the preparation of thin-sections and mounted with Lakeside 70 on a glass slide. Heat is then applied to the mountant with a Bunsen burner to a temperature just below the point at which the Lakeside becomes very fluid. If this is done for about 1 min, the fluid will penetrate and bind the clay and other minerals but will affect only slightly the calcareous material. If heating is prolonged to 5 min, much of the calcareous constituents will be bonded, in addition to bonding of the noncarbonate components. After mounting, the carbonate material is dissolved in 20 % acetic acid, or dilute to concentrated hydrochloric acid (depending on factors mentioned above). By using this procedure, i.e., mounting an unetched surface, the calcareous features are subdued and mainly the textures and structures due to clay and other insolubles are visible. TheLee-Hedberg technique has been used with success in the study of traces of insoluble material in stromatolites, irregular algal Spongiostromata, and in the investigation of non-carbonate components within internal sediments versus those of the reef-limestone framework (WOLF,1963a). In the methods advocated above, the acid reactions with clay may alter the latter and one should be circumspect in the interpretation of the exact clay mineralogy. Techniques for the separation of clays with a minimum destruction or alteration are given below. It has been customary to separate clay minerals from the carbonate rocks by acid digestion. Acids react with clays, however, and a number of methods have been proposed to minimize destruction. According to GRIM(1953, p.296), the reaction of clay minerals with acids varies with: (I) nature of acid $2) concentration of acids; (3) acid/clay ratio; ( 4 ) temperature; (5) duration of treatment; (6) group of clay minerals (e.g., montmorillonite is more sensitive than illite or kaolinite); (7) type of clay mineral within a group (e.g., Mg-rich montmorillonite is more soluble in acid than Al-rich ones, whereas Fe-containing types are intermediate in sensitivity to acids); (8) degree of crystallinity; and (9) particle size. ROBBINS and KELLER (1952) made experiments on montmorillonite to check the effects of HCl acid on that mineral. They reported that 57.1 % of the original montmorillonite sample dissolved in 6 N HCI in 96 h. LLOYD(1954) used a cation exchange resin and I /10 N HCI for the separation of clay minerals from limestones. The use of the resin resulted in three times as much clay in contrast to the samples that were digested in hydrochloric acid. RAYet a]. (1957) stated that strong acids dissolved also some of the hydrated micas, and ferri-ferrous chlorites, in addition to some members of the montmorillonite family such as hectorite. Their experiments on hectorite indicated that the use of both HCI and formic acids for extracting acid-sensitive clay minerals from carbonate rocks is restricted to room temperature and a p H no lower than 2. The reactions are slow under these conditions, especially for dolomite. The resin Amberlite IRC-50, however, can be employed at higher temperatures and the

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

277

reaction times are favorable as far as limestones are concerned and are even faster for dolomite. Acetic acid seems to be as effective as the resin for calcitic material but less so for dolomite, because of the very slow rate of dissolving of this mineral. The cation exchange resins cause solution of the carbonate in a very weakly acidic solution of relatively high pH. Amberlite IRC-50 when ionized is in the form of COO-, and when non-ionized is in the form of COOH, and derives its exchange activity from carboxylic acid. The Amberlite’s hydrogen form in distilled water gives rise to a pH of 6 or a H3O+ concentration of about 10-6 molar. This is equivalent to a Haof concentration of about 9 * 10-3 molar for a 4.4 molar solution of acetic acid (1:3 by volume); about 3.3 * 10-2 molar for a 6 molar solution of formic acid (1 :3 by volume); and about 3 molar for a 1 :3 solution of HCl, all at room temperature (RAYet al., 1957). As the H30+ concentration is the major parameter controlling the rate of reaction of the various acid solutions with the clay minerals, it is significant to note the low hydronium concentration on using the resin. It is a million times smaller than that of hydrochloric acid solutions. OSTROM (1961) found that “. . . expansible minerals, or those with expansible constituents, are the most susceptible to acid reaction. No reaction was apparent from X-ray diffraction curves between nonexpansible clay minerals and acetic acid solutions of 16.6 A4 and HCI solutions of 10 M concentrations for 72 h.” (For precise data of the experiments see Ostrom’s original paper.) Ostrom recommended the following method for the separation of clay minerals from carbonate rocks utilizing weak HC1 or acetic acid. (I) Remove possible adhering foreign particles by washing and scrubbing (or using an ultrasonic vibrator) approximately 150 g in distilled water. (2) The sample is allowed to dry. (3) Crush the sample to pass a 60-mesh sieve. ( 4 ) Place a small amount of the crushed material (less than 10 g) in a 100ml of 0.5 Macetic acid. If a reaction is noticeable, the sample consists of calcite with or without an admixture of dolomite and the procedure given below is followed. If no reaction is apparent, the sample probably consists of dolomite (or some other carbonate). The same procedure is used except that a HCI solution of less than 0.1 1 M concentration is utilized. (5) The unused minus 60-mesh material is mixed with 100 ml of distilled water in a 1,500-ml beaker. (6) Add 1,000 ml of acetlc acid of less than 0.3 M concentration. (7) Stir periodically until reaction ceases; reaction may last up to several days. (8) Separate impotent liquid from solid residue by filtering or decanting. (9) Additional acid is added and the process repeated until &#inch very fine material covers the undissolved limestone after settling. This material consists of clays and other insolubles. N.B. During the foregoing steps undissolved limestone should be present at all times to minimize clay alteration. (10) Separate clay by mixing the solids with 300 ml of distilled water. After

278

K. H.

WOLF, A.

J. EASTON AND S . WARNE

2 min settling period, decant the mixture into a 1,500-ml collecting beaker. (11) Repeat process until liquid decanted is essentially clear. (12) The solids in the 1,500-ml beaker are washed by decanting or filtering off the supernatant liquid until the fine-grained solids are thoroughly dispersed. (13) Permit the suspension to settle for 2 h before preparing oriented aggregates of the less than 2 mp clay mineral fraction. (14) Use eye dropper to transfer dispersed clay to glass slides. It seems that if precise investigations are to be made, e.g., on trace elements. a slight modification of the above procedure may be advantageous. Instead of waiting until the reaction ceases (7), the insoluble material could be removed from the beaker every few hours to minimize the time of exposure of the clays to the acid. BISQUEand LEMISH (1958) used the following approach to minimize damage of the clay structure as determined by X-ray diffraction: “50 g of finely powdered rock (passing No.100 sieve), 50 ml of dispersing agent (prepared by dissolving 40 g of sodium metasilicate-NazSiOa.9H~O and 7 g of sodium carbonate-NazCOa in water and diluting the solution to 1 I), and several hundred milliliters of distilled water were agitated for 5 min in a mechanical laboratory stirrer. This suspension was then transferred into a 1,000-mlgraduated cylinder and more water was added. The system was again tlioroughly agitated with a mixing plunger and allowed to stand for 7 h at room temperature. A 50-ml aliquot was centrifuged for 15 min at 2,500 r.p.m. and the supernatant decanted, leaving a heavy slurry clinging to the bottom of the bottle. Of distilled water 10 ml were added and the slurry stirred into suspension. Exactly 4 ml of the resulting suspension were drained onto a 25 x 46 mm glass slide which was previously placed in an oven pre-heated to 60 “C. After several hours the dry slide is found to be covered with a uniform coating suitable for X-ray diffractometer investigation”. J. Lemish stated (personal communication, 1964) that “the method is effective and sensitive to detection of clay in carbonate rock. In experiments on mixtures of clay and pulverized limestone, the method has proven to be sensitive to 0.1 % clay. On natural rocks the flotation method is at best roughly semi-quantitative or relatively comparative if care is taken to standardize the method; the method is effective for the qualitative determination of clays in the carbonate fraction”. PETERSON (1961) extracted clays from carbonates “. . . by leaching the finely ground specimen. at room temperature in a solution of acetic acid buffered at pH of 4.5 with lithium acetate.” Dolomite takes up to 1 day to dissolve at this pH, whereas calcite leaches much faster. “Li+ was chosen because it would be one of the ions least likely to replace other ions already in the clay structure (GEDROIZ, 1922: GRIM,1953, p.147). During the leaching process, Ca2+ and Mg2+ ions are also produced. To keep the concentration of these ions low, a large excess of leaching solution was used. The solution was well buffered and change in acidity was less than 0.5 p H unit during the digestion of a specimen.”

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

279

Investigations of trace elements of both the carbonate and non-carbonate fractions depend, as in the case of clay minerals, on separation procedures that permit a minimum of contamination. HIRSTand NICHOLLS (1958) carried out experiments which showed, in agreement with the results of others quoted above, that HCI attacks the clay minerals considerably whereas the effects of acetic acid are less severe. The amounts of trace elements determined from the carbonate fraction were constantly less when acetic acid was employed in the digestion as contrasted to HCI. Although it is clear that the acetic acid is more effective than HCI acid in separating procedures, the possibility still exists that minor changes in trace elements are caused by acetic acid. MCCREA(1950) presented a method of preparing carbonate rocks crushed to 200 mesh for l*O/l60 isotope analysis by using phosphoric acid. DEGENSand EPSTEIN(1962) in their study of isotopes in coexisting carbonates, cherts, and diatomites, used phosphoric acid to obtain a separation of the carbonate from the non-carbonate constituents. Where small amounts of carbonate still adhered to the chert, they were removed by treatment with 2ni HCI for approximately 5-10 min. This HCI treatment did not affect the 1 8 0 / 1 6 0 ratio of the chert as demonstrated experimentally. HUNTand JAMIESON (1956) described a method for the extraction of organic matter from samples that have been crushed to a particle size of about 15 p. MCIVER(1962) increased the efficiency of this extraction method by using an ultrasonic processing tank. OPTICAL IDENTIFICATION OF CARBONATE MINERALS

Information on the optical and physical properties of the carbonate minerals are to be found in numerous text and reference books such as those by WINCHELL (1956), STRAKHOV (1957), BERRYand MASON(1959), MOOREHOUSE (1959), and DEERet al. (1962). No duplication of this readily available material is required here, therefore, except for some data on the relationship between the refractive index and chemical composition. The carbonate minerals are notoriously difficult to identify in thin-sections with a petrographic microscope. A number of methods have been proposed, however, that facilitate the determination of the approximate chemical composition of these minerals. They are mainly based on the determination of the refractive index from mineral grains by the oil-immersion method or in thin-section with the use of the universal stage. As the refractive index of different isomorphous carbonate series overlap, staining, spot tests, or chromatographic methods (RITCHIE, 1964) may be required to determine the particular mineral. When a powder of rhombohedral carbonate minerals is examined, most of the crystal fragments will rest on the prominent rhombohedral cleavage (1011). The no can be measured from any grain. The cleavage fragments resting on (loil),

280

K. H. WOLF, A. J. EASTON A N D S. WARNE

1.56

1.58

1.60

1.62

1.64

-na'(ioii)

1.66

1.68

1.70

1.72

1.74

1.76

Fig.4. Chart for determining nc for the trigonal (rhombohedral)carbonates, provided no and ne' are known. (After LOUPEKINE, 1947, by permission of The American Mineralogist. See also BLOSS, 1961.)

however, will only give ne' (symbolized ne'cloil,). Once no and ne' have been measured, n e can be determined from Fig.4 (LOUPEKINE, 1947; BLOSS, 1961, p.140). The values obtainable from this figure are reported to be accurate to within f 0.004. If a correction factor is applied, as discussed by LOUPEKINE (1947), this error is theoretically reduced to k 0.001. Knowing the refractive indices, and establishing the isomorphous series present, the approximate composition of the crystalline carbonate minerals can be determined from Fig.5, which in this case utilizes

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

Mol.

per

28 1

c e n t

Fig.5. Variation of no with composition in the trigonal carbonates. (Mainly after DEER et al., 1962, 1947, by permission of The American Mineralogist.) and TR&ER,1959. Modified after KENNEDY,

no. In the publications listed above other tables and diagrams using both ne and no are available. USDOWSKI (1963, p. 100) used the immersion method for the determination of ankerite and obtained no values of 1.717-1.726. From this he concluded that the composition should be C ~ M ~ O . ~ ~ F ~ O . ~ toZ CaMg0.52(C03)~. (CO~)Z Chemical analysis of some of the ankerite indicated satisfactory agreement with the optically determined compositions.

282

K. H. WOLF, A. J. EASTON AND S. WARNE

GRUSS(1958) used the immersion method successfully in establishing various compositions of Mn-, Fe-, Ca-, and Mg-carbonate minerals (GRUSS,1958, fig.8, 12, 23) formed by the replacement of limestones. Gruss showed, for example, that echinoid and mollusk fragments have ne values ranging from 1.658 (=calcite) to 1.78 (=rhodochrosite and possibly siderite). To determine the mode and rate of replacement, he performed experiments in which he succeeded in replacing the Ca in calcite by Mn. Determining the refractive indices, Gruss found a measurable progressive increase of Mn content until no further change occurred at 70% MnC03. BURGER (1963) also used the immersion method in determining the refractive indices and from them the composition of the carbonate minerals. He was able to plot, for instance, changes of Mn content related to the location of ore deposits. He found, however, that the compositions determined by this method are only approximate. The recognition of the carbonate minerals in thin-sections is considerably facilitated by utilizing a universal stage. WALGER(1961) used the so-called Schumann method (SCHUMANN, 1948), or a modification thereof. This method is based on the size and shape of the indicatrices of the trigonal (rhombohedra]) carbonates. Measurements are taken of the angle between the optical axis and the normal of the direction within the indicatrix where ne’ = nr (no> nr > ne, where ni is the refractive index of the mounting medium; Fig.6). This angle of rotation is measured with the universal stage in the following manner: (I) A4 is in E-W position; Az=OZ; A3=0”. (2) Polarizer is in N-S position. (3) Analyzer and Bertrand lens inserted. (4) Turn about A1 until N-S isogyre coincides with N-S line of cross-hair. A principal section is parallel to A4. ( 5 ) Tilt about A4 until melatop coincides with center of cross-hair. Read [*. (6) Remove analyzer and Bertrand-lens. (7) Tilt about A4 in opposite direction until the Becke line and relief disappears, then ne’ = na. Read i*.(8) [* and *; are corrected according to Snell’s law to obtain [ and 2.(The correction of S* is not required if the segment measured is close to na.) (9) 5 and 2 = Po. (10) Use Fig.6 to determine composition. WALGER (1961) mentioned that staining is required to determine the particular isomorphous series before a final determination is possible. Walger stated that based on FRIEDMAN’S (1959) staining techniques not all series can be identified. This limitation, however, has been eliminated by the staining scheme of WARNE (1962) given here in the appropriate section. The use of Canada Balsam or Lakeside cement 70C as mounting medium (nt = 1.537 or 1.54) limits the application of the method described above. Walger pointed out, however, that mounting media with nr = 1.57 and 1.665 are available, and permit the examination of the whole range of carbonates under consideration here (nr = 1.57 for Phthalopal G, many polyester-resins such as Standofix, Palatal, Legural KR25; nr = 1.665 for Aroclor No.4465 manufactured by Monsanto Chem-

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

283

ical Co., St. Louis, Mont., U. S. A.). As Aroclor has a strong dispersion ( n ~ - n ~ = 0.019), it is advisable to use Na-light. GILBERT and TURNER (1949) described a universal stage method to distinguish between calcite, dolomite, Fe-dolomite and ankerite; and HOWELLand DAWSON(1958) use a similar technique as described above for iron-bearing dolomite. WINCHELLand MEEK(1947) suggested that the diagnostic birefringence/ dispersion ratio is useful in discrimination between various carbonates in thinsection. Both SCHUMANN (1948) and WALGER (1961), however, discussed the limitations of this method. During Walger’s investigations he met unexpected difficulties which have not been solved as yet and it is impossible, therefore, to make a final decision regarding the applicability of the method advocated by Winchell and his co-workers.

Fig.6. Variation of eo with composition in the minerals of the calcite group. (After WALGER, 1961, by permission of the Neues Jahrbuch fur Mineralogie, Monatshefte.)

284

PLATE I

A

K. H. WOLF, A. J. EASTON AND S. WARNE

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

285

B

286

K . H. WOLF, A. J. EASTON A N D S. WARNE

The limitations of using the methods mentioned above in determining the composition of carbonate minerals have been mentioned by WAYLAND (1942) and Burger (1963), for example. In the cases of simple solid solution substitutions, e.g., MgC03--MgFe(CO3)~-FeC03, the figures by KENNEDY(1947) and WALGER (1961) can provide a sufficiently accurate means for rough estimates. Substitutions are often more complicated, however, and instead of one cation two or more take the place of Ca, for instance. Particularly illuminating are the discussions and data by LOGVINENKO et al. (1961). They pointed out that most information on the isomorphism of carbonates is related to binary series, whereas in fact many are polycomponent systems, such as (Fe, Ca, Mg, Mn) C03. One of the examples of sedimentary (i.e., low-temperature) monomineralogic carbonates determined by them had the composition (Fe49.67-85.04 Ca3.54-38.80 Mg3.99-20.47 Mno.ol-9.1z)COa. Presently available optical methods alone, of course, cannot reveal such complicated compositions.

ELECTRON-MICROSCOPE EXAMINATION OF CARBONATES

The electron microscope has already been used for some time to reveal microfeatures of fossils, but it has not yet been employed everywhere to its fullest advantage in carbonate petrology. WATABE et al. (1958), GRUNAU (1959), GRBGOIRE (1961, 1962), WATABE and WILBUR(1961), HAY and TOWE(1962), and ROSTOKER and CORNISH (1964), for example, studied micro-organisms. ALBISSIN and RANGO(1962) investigated corrosion features, and GRBGOIRE and MONTY (1962) examined the cryptocrystalline nature of stromatolites. M. I. Whitecross (personal communication, 1964) has shown that the Renalcis unicellular Algae in certain limestones (WOLF,1963a, 1965a) are crystalline in nature (Plate IA,B). The presence or absence of crystals as well as their size and shape may be investigated with the electron microscope using a surface-replica method. Since the carbon-replica technique was first reported (BRADLEY,1954), it has been used in examining the surfaces of a wide variety of materials. Though there have been

PLATE I (813.284-285) A. The central part shows an electron-microscope enlargement of a section of a Lower Devonian 1965a).Note the gradation into larger crystals of the surrounding unicellular Alga Renalcis (WOLF, somewhat coarser, matrix. The Renalcis cells cannot be resolved by an ordinag petrographic microscope and are seen as dense, cryptocrystalline specks. (Photo by Dr. M. I. Whitecross, Australian National University.)

B. Electron-microscope enlargement of the coarser crystalline matrix surrounding the Renalcis cells featured in Plate IA. (Photo by Dr. M. I. Whitecross, Australian National University.)

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

287

many modifications, it consists essentially in transferring an impression of the surface in question through some intermediate steps to a thin layer of carbon which can be examined in the electron microscope. Carbon replicas are commonly shadowed in vacuo with a heavy metal to enhance their contrast and three-dimensional appearance in the electron beam (BRADLEY, 1906). Plates IA,B were taken from replicas using the following procedure, employed by Dr. M. I. Whitecross of the Australian National University. The rock surface was polished with carborundum powder (grade 500), washed and etched with saturated disodium E.D.T.A. solution for 1 min. The surface was washed again, dried thoroughly and the chosen area flooded with a 20 % solution of Bedacryl 122X(I.C.I.). When the solvent had dispersed, a plastic film was left forming a negative replica of the rock surface on its lower face. Stripping the plastic film from the rock surface (to which it had become firmly “keyed”) was simplified if the rock plus film was immersed for a couple of minutes in water. The stripped film, with its replica surface uppermost, was then bonded to a microscope slide, given a layer of carbon and shadowed with gold palladium in the usual way. The final carbon replicas were obtained by dissolving the Bedacryl with acetone and picking up pieces of the carbon film on electron-microscope grids. SHOJIand FOLK(1964) recently investigated fractured limestone surfaces with an electron microscope and were able to correlate the features observed with those obtained with an optical microscope. Significant for trace element and diagenetic studies and environmental interpretations are the liquid inclusions observed in calcitic material by the above two investigators. Solution to the problems of genesis of the numerous cryptocrystalline micrite types listed by CHILINGAR et al. (1967) and WOLF(1963b, 1965b) may well rest on detailed electron-microscope examinations.

STATISTICAL AND RELATED MICRO-FACIES STUDIES

A number of diverse techniques have been employed in carbonate petrology that rely heavily on a statistical basis for genetic and stratigraphic interpretations. FAIRBRIDGE (1954) discussed the advantages, limitations, and applications of micro-facies investigations. Fairbridge quoted CUVILLIER (1951b) as stating that an oil survey of Aquitaine (France) “. . . required the application of a system of stratigraphic correlation in which the micro-facies played a much more important part than the microfauna. In fact, among the formations encountered both in outcrop and borehole, especially those consisting of hard rocks, calcareous, marno-calcareous, siliceous, etc., correlations by microfaunas of Foraminifera from washings are hardly practicable. Thousands of thin sections of these rocks, systematically sampled, have permitted, on the other hand, the realization of a

288

K. H. WOLF, A. J. EASTON AND S. WARNE

detailed stratigraphic subdivision which embodies all the most characteristic microfacies.” The more pertinent micro-facies features of carbonate rocks are morphologic grain types; matrix types; morphologic types of sparry calcite cement and recrystallization sparite; grainlmatrixlcement ratios; degree and amount of replacement and recrystallization; fossils and fragments thereof without a need for precise identification (FAIRBRIDGE, 1954); certain diagenetic products; and other textures, structures and morphologic characteristics. CUVILLIER (195 1a), HAGN (1955), REY and NOUET (1958), GRUNAU (1959), HANZAWA (1961) and SACAL (1963) have published books on micro-facies, some containing over 100 photomicrographs, that illustrate the method discussed by FAIRBRIDGE (1954), among others. Micro-facies studies have been much improved by the handling of the information in a statistical manner as done with success by CAROZZI (1950, 1958) and STAUFFER (1962), for example. BANKS(1950) described a log for recording the types of individual constituents as well as the gross rock lithology. This kind of log, with modifications, is very useful in the description of carbonate sediments. Very detailed logs may resemble those prepared by BOUMA(1962), and MENNING and VITTIMBERCA (1962) for terrigenous sediments. To complement the various symbols and verbal descriptions of logs, a number of exploration companies have resorted to adding photomicrographs that greatly enhance the visualization of sediment lithology. CAROZZI (1950, 1958) developed a technique which consists of preparing thin sections of carbonate rock specimens that have been collected at an interval of about 1 ft. The spacing is usually adjusted to suit the particular requirements. In precise investigations, thin-sections prepared of samples taken every 4-6 inches approaches the ideal of continuous sampling. Carozzi measured the following parameters in thin-sections: ( I ) maximum diameter of detrital grains (clasticity-index), which gives an idea of the power of transportation, and the number of detrital grains (frequency index), which furnishes information about the load of the current; (2) microfaunas (frequency and maximum apparent diameter); (3) matrix (amount, texture and composition); and ( 4 ) authigenic minerals (frequency and maximum apparent diameter). The curves based on these parameters are valuable in particular as they not only assist in correlation but permit detailed paleoenvironmental reconstructions as has been illustrated by Carozzi and his co-workers in their numerous well-known publications. In addition to presenting frequency curves that give the vertical distribution of numerous components in the sedimentary column, STAUFFER (1962) prepared contour maps of these parameters, thus illustrating the regional paleoenvironmental pattern of distribution. The parameters he used for the contours are as follows: composition and percentages of allochemical grains, sparry calcite cement, and recrystallized calcite; individual allochemical grain types such as Bryozoa, cri-

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

289

noids, intraclasts, algal fragments, fusulinids; the largest diameter of different grain types; and others. SLOSSand COOKE (1946) proposed spectrochemical sample logging of limestones; and KUDYMOV(1962) presented ample evidence of the usefulness of analyzing for major and minor elements in both practical and research geology. In the investigation of Recent carbonate sediments, FOLK(1962), FOLKet al. (l962), and FOLKand ROBLES(1964) have used a statistical approach in recording grain size, sorting, and skewness that resulted in some interesting information regarding similarities and dissimilarities between carbonate and terrigenous sediments. For an example of grain-size, frequency, rounding and sphericity studies applied to ancient limestones, the publication by FLUGEL and FLUGEL-KAHLER (1962) is recommended by the writers. HARBAUGH and DEMIRMEN (1964) gave an example of factor analysis in stratigraphic work (see also IMBRIEand PURDY,1962; and IMBRIE, 1964).

X-RAY RADIOGRAPHY

A number of recent publications recommended the application of X-ray radiography for bringing out the sedimentary structures in terrigenous rocks (CALVERT and VEEVERS, 1962; HAMBLIN, 1962; RIOULTand RIBY, 1963). The senior writer has attempted without success to apply the same method to a few homogeneous limestone samples. Acid-digestion of these specimens indicated that they were too pure to have caused differential passage of the X-rays. Better results are expected with carbonate rocks containing non-carbonate impurities which reflect the primary depositional pattern.

SPOT TESTS FOR CATIONS IN CARBONATES

It has been mentioned in an earlier section that staining and spot tests may be made on carbonate minerals to help in identifying the isomorphous series as well as possible minor elements present. Spot tests for some of the cations usually associated with carbonate minerals, and a short description of the techniques, results, and limitations are presented in Table 111. For more information on spot tests the reader may wish to consult a more comprehensive work on the subject such as that of FEIGL (1958). The following aspects should be noted: (1) The quantities of acid used are only approximate and should be added dropwise to approximately 100 mg of the sample. ( 2 ) The neutrality or acidity should be tested by the use of Universal indicator paper. The adjustment may be made either by the addition of more sample or acid.

TABLE I11

h,

\o

0

SPOT TESTS FOR CATIONS IN CARBONATES ~~

Element

Solvent

Solution

Reagents

Procedure

Reaction

Notes

Fe3+

lO%v/v HC1 (2 ml)

Slightly acid.

lO%w/v potassium thiocyanate solution.

Place 1 ml of test solution in a test tube, add 3 drops of reagent.

Red coloration due to ferric thiocyanate.

Limit of identification (30 p.p.m.).

Ca

lO%v/v HCI (2 ml)

Slightly acid.

(I) 300 mg ammonium chloride (2) S%w/v ammoniumoxalate solution.

Place 2 ml of test White crystalline precipitate: solution in a test tube, add reagent calcium oxalate. I. Then add 1 ml of reagent 2. Heat to boiling, add excess ammonium hydroxide, and continue boiling for several minutes.

Sr

lO%v/v HC1 (2 ml)

Neutral.

0.2%w/v sodiumrhodizonate solution.

Place 1 drop of test solution on a filter paper impregnated with saturated potassium chromate and then dried. After 1 min add 1 drop of reagent.

Brown-red fleck on circle (strontium rhodizonate).

(I)In case of ferrodolomite: after reagent I, add 1 ml of Brz water, boil for 1 min, and then add ammonium hydroxide until neutral. Centrifuge off the precipitate and discard; then add reagent 2, and boil for several minutes. (2) In rhodochrosite: after reagent I, add 1 ml of bromine water, boil for 1 min, and then add 3 ml ammonium hydroxide. Centrifuge off precipitate and discard; then add reagent 2 and boil for several minutes. (Limit of identification is 600 p.p.m.) In case of rhodochrosite: dissolve sample, add 1 ml of bromine water, boil for 1 min, and then neutralize with ammonium hydroxide. Centrifuge off the precipitate and discard. Then continue as under procedure. (Limit of identification is 100 p.p.m.)

d

"G

Mg

Fez+

Mn

lO%v/v HCl (2 ml)

Slightly acid.

(1)0.1 %w/v titan yellow solution (2) lO%w/v sodium hydroxide solution.

Place 5 ml of reagent I in a test tube. Add 10 drops of test solution; then add reagent 2 dropwise until precipitate forms.

Supernatant liquid and precipitate are red (magnesium dye complex).

In case of siderite or rhodochrosite: dissolve sample, make volume to 5 ml, add 300 mg of ammonium chloride, and then add 1 ml of bromine water. Boil for 1 min and neutralize with ammonium hydroxide. Centrifuge off precipitate, make centrifugate just acid with HCI. Then add 5 ml of reagent I followed by reagent 2 dropwise until a precipitate forms; allow to settle. The precipitate alone is colored red due to interference of ammonium salts. (Limit of identification is 150 p.p.m.)

lO%v/v HCI Neutral. (2 ml) or 3 %V/V HzS04 (3 ml)

(I) 0.2%w/v 2,2-dipyridyl (in 1.5 %v/v HCI solution). (2) 25 %w/v sodium acetate solution.

Place 2 drops of test solution in a test tube, add 2 drops of reagent I, and then 5 drops of reagent 2.

Pink coloration (ferrous When testing for Fez+ in dipyridyl complex). rhodochrosite: increase volume of test solution to 5 ml, reagent I to 1 ml, and reagent 2 to 5 ml. (Limit of identification is 20 p.p.m.).

3 %v/v HzS04 Acid. (5 ml)

(I) 1 %w/v silver nitrate solution. (2) 20U mg ammonium persulphate.

Place 5 ml of test solution in a test tube. Add 2 drops of phosphoric acid, then add drop of reagent 1. This is followed by reagent 2. Boil for 1-2 min.

Pink coloration in supernatant liquid (KMn04).

When testing for Mn in siderite: increase phosphoric acid to I ml and reagent 2 to 500 mg. (Limit of identification is 15 p.p.m.)

5*z

5 8

*

2 2 U

*

%.e

E

% v1

6 Z

4 >

P

4

0

> P

8

5 a

v)

292

K. H. WOLF, A. J. EASTON AND S. WARNE

(3) The reagents should in the case of organic compounds be freshly prepared (daily). To increase the sensitivity of spot tests on filter paper, a circle inch) is pencilled on both sides of the filter paper with a white grease pencil and warmed over a low Bunsen flame to congeal the grease. The test drops are applied within the circle in order to concentrate the reaction. Where precipitates are formed, the solution may be drawn from the drop by blotting the under side of the test circle. Thus the color of the precipitate can be seen more easily.

(a

CHEMICAL ANALYSIS OF CARBONATE MINERALS AND ROCKS

Methods for the determination of the major and some minor components of carbonates by either wet or dry, o r a combination of both techniques are presented here in some detail. It is not possible to present data on analytical techniques of most of the trace elements and only a table is given to indicate the method usually employed (Table IV,V). The techniques described here have been utilized on the analysis of ten samples and the results are shown in Table VI. The basis of the earlier schemes for the wet chemical analysis of limestones was mainly formulated in relation to the industrial application of the material. Often the analysis was restricted to the determination of acid insoluble residue, iron, calcium and magnesium. The carbon dioxide was either calculated from the calcium and magnesium contents or determined by loss on ignition. This simplified analysis satisfied the industrial requirements and was not expanded until geological investigations required a more detailed knowledge of the carbonate material. (1930) shows this expansion of limestone analyses in detail. The work by NORTH Since that time, however, the accuracy of some of the analytical methods for the determination of minor elements, e.g., Fey Mn, P, Ti, Cr, and Al, TABLE IV MAJOR AND MINOR ELEMENT ANALYSIS'

Element

Ca Mg Fe Mn Ti

Percentage 0.1-1

1-10

> 10

b (*Is%) b(55%) a (52%) a (52%) a (f2%)

b,c (f2%) b,c ( M %) a,b (*2%) a,b ( 5 2 % ) -

b,c ( 4 2 % ) b,c (52%) b (32%) b (&2%) -

a = spectrophotometricanalysis; b= E.D.T.A. titration; c = gravimetric analysis.

293

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

TABLE V TRACE ELEMENTS ANALYSIS~

U

Na K Li Rb Sr

cs Sb As Ba Be B Br CI

+ + + + + ++ +

U2

Th2 Se Ag Sn Ti W V Zn Zr Ra2

-

co

+ + +

cu F

Ga Ge Au Pb Mn Hg Mo Ni

-

1

Cd Cr

_____

-

-

U

b

+

P

+ +-

-

P

+ + + ++ +-

-

P P

-

-

-

+ + + + +-

+

P P

+ + +

C

+ + + P + + + + + + P + P + + P + -

d -

+ +-

+ + +-

+ + + + +-

Neutron activarion. With the exception of the halogens, Li and Be, most other elements, including the rare earths, can be determined by this technique. Although this method has the advantage of sensitivity, the equipment involved is costly. This is the only technique available for certain elements at the concentrations in which they occur. (a) Flame-photometry. Although a number of elements have been indicated in the table as being determinable by flame-photometry, with the exception of the alkalies Na and K, complex separations are often necessary to remove major elements that would otherwise interfere in the determination. Separation of organic complexes containing the element to be determined increases the sensitivity, and allows the determination of elements which otherwise would not be practical. (b) Spectrometry (copper electrodes). Extra sensitivity is obtained by the use of copper-spark emission techniques. The great advantage of spectrographic equipment is that a large range of elements may be determined at the same time. (c) Spectrophotornetry. This technique enables the determination of a large number of elements, although the time involved is sometimes greater than that required by other techniques. Ionexchange separations have assisted in the removal of interfering elements. (d) X-ray spectrograph (X-ray fluorescence). Similar to spectrographic techniques, the same sample may be used for the determination of a number of elements, particularly those with high atomic numbers. The sample may also be stored for future reference.

+

= determination possible; - = determination impossible; P = Explanation of symbols: determination by this technique preferred. Neutron activation is the technique preferred for these elements.

TABLE VI CHEMICAL ANALYSIS OF SOME RECENT AND ANCIENT CARBONATES ROCKS

(Determined by A. J. EASTON)

I

Sample No.

Moisture (%) Loss on ignition (%) Acid insoluble residue (%) CaO MgO Fez03 FeO MnO Ti02 Crz03 Pzos AhOs Na K Sr S (total) c1 Total (%)

0.58 44.80 0.17 50.60 2.54 0.01 1 0.005 0.003 <0.001 0.002 0.06 0.08 0.59 0.03 0.40 0.18 0.53 100.57

2 0.42 44.79 0.05 49.27 2.99 0.017 0.003 <0.001 0.002

<0.001

0.03 0.04 0.58 0.02 0.56 0.11 0.39 99.26

3

2.09 48.18 0.06 39.78 8.29 0.017 0.003 <0.001 0.001 <0.001 0.01 0.11 0.67 0.04 0.40 0.07 0.16 99.87

4 0.10 42.91 1.79 53.61 0.51 0.02 0.14 0.022 0.03 0.003 0.17 <0.01 0.01 0.02 <0.01 <0.01 0.33 99.66

5

0.11 42.68 2.05 53.06 0.80 0.055 0.16 0.056 0.005 0.002 0.30 <0.01 0.006 0.01 0.04 0.04 0.09 99.43

6 0.05 39.91 8.14 49.50 0.76 0.16 0.65 0.046 0.008 0.002 0.33 0.27 0.02 0.02 0.20 0.20 0.06 100.31

7 0.09 46.80 0.82 30.44 21.40 0.09 0.19 0.01 1 0.004 0.003 0.07 <0.01 0.03 0.01 <0.01 <0.01 0.16 100.11

8 0.01 45.51 2.90 32.45 18.62 0.018 0.047 0.002 0.013 0.003 0.10 0.13 0.04 0.02 0.06 <0.01 0.14 100.04

9 0.11 44.58 11.85 7.85 34.90 0.08 0.28 <0.001 0.013 0.001 0.13 0.05 0.03 0.04 0.04 <0.01 0.14 100.09

10

0.07 40.05’ 0.06 0.22 6.07 n.d.2 50.62 2.66 n.d.2 n.d.2 <0.01 n.d.% 0.06

0.02 n.d.z n.d.2 n.d.2 99.83

Sample No.1. Recent lagoon sample of Heron Island, Great Barrier Reef, composed of unconsolidated fine-grained calcarenite with constituents of aragonite, and low-Mg and high-Mg calcite (WOLF,1963a.) Sample No.2. Heron Island beach rock composed of aragonite-cemented skeletal calcarenite. Constituents: aragonite, low-Mg and high-Mg calcitic organic debris. (WOLF,1963a.) Sample No.3. Lithothamnion (algal) colony of Heron Island. Note high Mg content. (WOLF,1963a.) Sample No.4. Algal biolithite from the Lower Devonian Red Hill limestone @lo) near Wellington, N.S.W. (WOLF,1965a.) Sample No.5. Algal micrite from a Lower Devonian Nubrigyn bioherm (Nub. 716) near Stuart Town, N.S.W. (WOLF,1965a.) Sample No.6. Algal calcarenite from a “turbidite” facies of the Tolga Formation, near Stuart Town, N.S.W. (WOLF,1965a.) Sample No.7. Dolomite from the G.R.G. 14 well, Georgina Basin, N.T. (Sample No.141, courtesy Bureau of Mineral Resources, Canberra, A.C.T.) Sample No.8. Dolomite in Kaibab limestone, west of Blue Diamond Hill, Blue Diamond, Nev. (Courtesy H. J. Bissell.) Sample No.9. Pellet magnesite, Lower Adelaide System, S. Austr. (Specimen from Australian National University collection, courtesy Department of Mines, Adelaide, S. Austr.) SampleNo.10. Sideritefrom Mammoth Black Ridge, Martin’s Well Station, S.Austr. DDH2,476 ft. 1 inch. (Courtesy Broken Hill Proprietary Co. Ltd., Whyalla, S. Austr.) 1 Corrected for 2

n.d.

= not

oxidation of Rz03 group. determined.

295

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

has been improved by the introduction of spectrophotometric instruments. In a similar way the introduction of the flame-photometer has increased the accuracy of the determination of sodium and potassium. The use of E.D.T.A. titrations for the determination of calcium, magnesium, iron and manganese now offers an alternative method to the gravimetric procedures. The methods given in this section include: ( I ) moisture and loss on ignition; (2) carbon dioxide; (3) main analysis: 3a-acid insoluble, 36-silica in the acid insoluble, 3c-Rz03, 3d-iron, 3e-manganese, 3f-titanium, jlg-chrornium, 3h--phosphorus, 3i-aluminum, 3j-calcium-gravimetric, 3k-calcium-E.D.T.A., 31-magnesium-gravimetric, 3m-magnesium-E.D.T.A.; ( 4 ) ferrous iron; (5) alkalies-Na, K and Sr; (6) total sulphur and sulphur trioxide; and (7) chlorine. A general scheme combining some of these methods is shown in Fig.7. The details of the analysis largely depend upon the particular interest in the sample, i.e., industrial or geological investigation. Spectrophotometric measurements In a number of the following procedures the element is measured by forming a soluble colored complex. The absorbance (ie., intensity of color) of the test solution is measured using a spectrophotometer and compared with a curve obtained by treating aliquots of a standard solution of the same element in a similar manner (A. I. VOGEL,1951). In all of the spectrophotometric methods it is possible to prepare a standard curve by taking various size aliquots and plot the absorbances obtained against the quantity of the element in solution. In this way the absorbance of the test solution may be quickly converted to the quantity of the element (in milligrams) present in the solution.

'

SAMPLE

SAMPLE

I

Dissolve in acid

Dissolve in ocld

I

I

I

I

Acid insoluble

residue 30 Ignite ;"

coo

I

I Weigh

MgO

I

Fuse

I

Sqlutlon

Fe

Ti

Mn

Cr

P

Al

Fig.7. Scheme of chemical analysis of carbonates.

I

Acid insoluble residue Adjust

&

P

Cr

Mn

Ti,,Co

V

Spectrophotometricolly

Mg

A1 Fe,

* E.D.T.A. titratbn

296

K. H. WOLF, A. J. EASTON AND S. WARNE

The water reference sample and solutions were held either in special glass tubes or flat-sided glass containers known as cells. Whichever type of container is used, the light path is of a fixed length, e.g., 1 or 4 cm. Determirlation of moisture and loss on ignition

The moisture and loss on ignition are determined on the same portion of the sample. Weigh 1 g of sample into a clean weighed platinum crucible and dry for 2 h in an oven set a t 105°C. At the end of this period remove the crucible and cool in a desiccator for 15 min before reweighing. Repeat the heating for 30 min more, cooling as before. The loss in weight of the crucible and sample is due to loss of moisture (HzO) and is recorded as a percentage of the sample weight. Then transfer the crucible to either a Bunsen burner or an electric furnace and raise the temperature slowly to red heat (600°C). Finally, heat the crucible at 1,000-1,lOO"C for 1 h, then allow the crucible to cool in a desiccator for '30 min and weigh. Repeat the ignition for 30-min periods at the higher temperature until a constant weight is obtained. The loss on ignition is the difference in weight of the crucible and sample after drying at 105"C, and the final weight after ignition. This is then calculated as a percentage of the sample weight. Loss on ignition will be the combined loss of carbon dioxide plus any other constituents present that are evolved at temperatures above 105"C (e.g., hydrocarbon compounds and organic materials as those in Lithothamnion in sample No. 3 in Table VI). Note: Where a large proportion of the sample is siderite, the loss on ignition must be corrected for the increase in weight due to the oxidation of the Rz03 group [i.e., FeO (from FeC03) + Fez03; and MnO (from MnC03) -+Mnz031. Determination of carbon dioxide

Two alternative methods are available for this determination, the first is usually reserved for samples high in carbon dioxide, whereas the second may be used regardless of the carbon dioxide content. Schotter flask (CLOWESand COLEMAN, 1944) In this method the carbon dioxide is liberated from a weighed portion of the sample by the action of phosphoric acid. The sample, separated from the 10 ml of 50% v/v phosphoric acid is placed in the flask and weighed. The acid is allowed to come into contact with the sample and the liberated gas leaves the flask through a trap containing sulphuric acid. After the reaction is complete, the flask is reweighed; the difference in weight is a measure of the carbon dioxide content of the sample.

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Absorption train (A. I. VOGEL,1951) This method uses the increase in weight of U-tubes containing soda-lime and calcium chloride to measure the carbon dioxide liberated by the action of phosphoric acid on a weighed portion of the sample. Main analysis Acid insoluble residue Weigh 1.0 g of .the sample into a 250-ml beaker and cover it with a watch glass. Add 150 ml of 25% v/v hydrochloric acid and warm the beaker and contents to 50-60°C for 30 min (BISQUE and LEMISH, 1959). After this period wash the cover glass into the beaker and filter off the insoluble residue through a 541 Whatman filter paper. Wash the paper three or four times with warm water and set the filtrate aside for the determination of the other elements. Ignite the paper containing the insoluble residue in a previously weighed platinum crucible. The heating should initially only be sufficient to dry the contents of the crucible, then increased slightly so that the paper is charred, a& finally increased to just red heat to ignite the paper completely. After the paper has been ignited, the heat is increased to about 1,OOO"C for 10-15 min. The crucible is allowed to cool in a desiccator for 30 min before weighing. Repeat the ignition until a constant weight is obtained. The weight of the ignited residue is reported as a percentage together with the strength of the acid (25 % v/v HCI) and the temperature to which it was initially heated (50-60°C). It should be appreciated that some clay minerals will also pass into solution with the carbonate portion of the sample, because certain clay minerals are slightly soluble. Organic insoluble matter will be destroyed on using the ignition method given above; and, therefore, if the acid insoluble residue including the organic matter is required, the filtration must be made through a weighed glass-sintered crucible. This is then reweighed after drying to a constant weight at 105°C in an oven. Complete analysis of acid insoluble residue (silica) Upon recording the weight of the platinum crucible plus the acid insoluble residue after ignition, the residue is then treated with one or two drops of sulphuric acid and 5 ml of hydrofluoric acid. The silica is then volatilized off by heating the crucible first on a water bath and then, when only sulphuric acid remains, by heating over a low Bunsen burner flame until all of the acid is fumed off. The heating is continued for approximately 10 min after which the crucible is allowed to cool in a desiccator for 30 min and then reweighed. The loss in weight is the weight of the silica present in the acid insoluble residue.

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Where a complete analysis of the other constituents of the acid insoluble residue is required, the residue from the treatment with HF-HzS04 is fused in the platinum crucible with 0.5 g of sodium carbonate. The fusion cake is dissolved from the platinum crucible with a minimum of 10% v/v hydrochloric acid and the solution is transferred to a beaker. This solution is then analyzed by the methods given in the sections on iron, manganese, titanium, chromium, phosphorus, and aluminium for the R203 group constituents; and the calcium and magnesium are determined on using the filtrate from the R203 group precipitation by the methods given in the sections on calcium-gravimetric, calcium-E.D.T.A., magnesium-gravimetric, and magnesium-E.D.T.A. determination. group (Fe, Mn, Ti,Cr, P,AI) (If the limestone analysis is required to include the acid insoluble residue with the carbonate portion, i.e., total analysis, the residue left after treatment with HFHzS04 is fused with sodium carbonate (0.5 g). Then the fusion cake is dissolved in a minimum of 10% v/v hydrochloric acid and the solution is added to the filtrate from the acid insoluble separation.) Add 1-2 ml of bromine water to the filtrate from the acid insoluble separation and boil for several minutes to oxidize any ferrous iron to the ferric state. Remove from the heater and add a few drops of universal indicator; then add ammonium hydroxide dropwise until the p H is raised to 7, i.e., neutral. (All members of the R2O3 group are precipitated after oxidation as hydroxides by the addition of ammonium hydroxide solution.) Replace the solution on the heater for 1-2 min, avoiding boiling, to coagulate the precipitate. Allow the precipitate to settle and filter through a 541 Whatman filter paper. Wash the precipitate in the filter paper three or four times with warm 1 % w/v ammonium nitrate solution. Set aside the filtrate. Dissolve the precipitate into a 250-ml beaker with warm 10% v/v hydrochloric acid, washing the dissolved salts through the filter paper with hot water. Increase the volume to 150 ml and reprecipitate as before. Filter off the precipitate and wash with warm 1 % w/v ammonium nitrate solution. Combine both filtrates and set aside for the determination of calcium and magnesium. Ignite the precipitate in a previously weighed platinum crucible. Heat slowly at first, increasing the temperature finally to approximately 1,lOO"C for 10-15 min. The crucible is allowed to cool in a desiccator for 30 min before weighing. Ignite again until a constant weight is obtained. The weight of the ignited precipitate is a sum of the weights of Fe, Mn, Ti, Cr, P, and A1 as oxides, depending on which are present in the sample. These are now determined separately by adding 1-2 g of potassium bisulphate to the crucible and fusing the ignited precipitate over a Bunsen burner flame in a fume cupboard. The crucible should only be heated at first sufficiently R203

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to cause the potassium bisulphate to just melt. The heat is gradually increased to avoid loss from the fusion due to “spitting”. Most of the fusion action is obtained below red heat; but it may be necessary to heat to red heat to obtain complete fusion of the ignited precipitate as the constituents are present as oxides. After fusion allow the crucible to cool to room temperature: this is most important for safety. Half fill the crucible with 3 % v/v sulphuric acid and place on a water bath or heater to dissolve the fusion cake. This may require several additions of the sulphuric acid before complete solution is effected. Allow the solution to cool, then transfer it to a 100-ml volumetric flask and adjust the volume with water. Shake the contents well to ensure thorough mixing. Then determine the constituents of the RzO3 group as given in the section below. Determination of total iron Two methods are available for the determination of iron depending upon the composition of the sample. The spectrophotometric method using the ferrous dipyridyl complex is suitable for samples containing < 5 % FenO3, but where this figure is exceeded an E.D.T.A. titration is more suitable (CHENGet al., 1952). Spectrophotometric method (RILEYand WILLIAMS, 1959). The iron present in the aliquot is reduced to the ferrous state as described below, then 2,2’-dipyridyl solution is added and the pH adjusted by the addition of a sodium acetate buffer. This results in a pink coloration. The absorbance of the solution is measured and compared with a standard iron curve. Place an aliquot containing 0.05-0.5 mg of iron as Fez03 in a 100-ml volumetric flask. If the iron content is totally unknown then initially use a 5 ml aliquot. Add 10 ml of 10% w/v hydroxylamine hydrochloride solution and set aside for 10 min to allow the iron in the solution to be reduced to the ferrous state. Add 5 ml of 0.2% w/v 2,2’-dipyridyl solution (prepared in 1.5 % v/v HCI), followed by 25 ml of sodium acetate buffer (272 g CH3COONa.3H20 per liter). Adjust the volume of the solution in the flask to 100 ml with water and mix. Measure the absorbance of the solution against water in a 1-cm cell using a spectrophotometer with the wave-length set at 522 mp. Compare the absorbance of the sample solution against a standard curve prepared by treating aliquots of a standard iron solution in a similar manner. Preparation of standard curve (Fig.8). A standard iron solution may be prepared by dissolving 0.1398 g of “specpure” iron sponge in about 2 ml of hydrochloric acid and diluting to 2 1 with water. Further, this solution should be diluted tenfold so that 1 ml will contain 0.01 mg of iron as FezOs. Place at least six aliquots of the standard iron solution, ranging from 0.050.5 mg, in 100-ml volumetric flasks and make the same additions of hydroxylamine hydrochloride, 2,2’-dipyridyl and sodium acetate buffer as before. After measuring

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0.6 1

Fig.8. Hypothetical “standardcurve” of absorbanceversus Fez03 content used in spectrophotometry. Wave length 522 mp; volume 100 ml; 1 cm cell.

the absorbances, construct a curve relating absorbance against milligrams of iron per 100 ml of solution. Determination of manganese The spectrophotometric method described below is used where MnO is < 5 %; but where the sample contains a high proportion of rhodochrosite, an E.D.T.A. titration is used (FLASCKA, 1953). The manganese in an aliquot is oxidized by the addition of ammonium persulphate and silver nitrate (catalyst) in an acid solution to form the pink permanganate color (WILLARD and GREATHOUSE, 1917). The phosphoric acid is added to prevent the interference of iron by forming iron phosphate, whereas the mercuric salt is added to prevent any trace of chloride from forming a turbidity with the silver ions in the solution. The absorbance of the solution is measured and compared with a standard manganese curve. An aliquot containing 0.05-0.5 mg of manganese as MnO is placed in a 100-ml beaker. If the manganese content is totally unknown, then initially use a 10-ml aliquot. On the other hand, if only a faint pink coloration is developed after oxidation, increase the size of the aliquot. Add 2 ml of the following solution to the beaker from a measuring cylinder. The solution is prepared as follows: dissolve 37.5 g of mercuric sulphate in 200 ml of concentrated nitric acid, then add 100 ml of phosphoric acid (85% strength) and 0.017 g of silver nitrate. Allow the solution to cool and dilute to 500 ml. Add 0.5 g of ammonium persulphate and adjust the volume to approximately 30 ml with water. Oxidize by boiling for 10 min. Allow the solution to cool to room temperature; if manganese is present then a pink coloration (KMn04) will develop. Transfer the solution to a 50-ml volumetric flask and adjust to volume with freshly boiled and cooled water. Shake well to ensure complete mixing. Measure the absorbance of the solution as soon as possible against water in a

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

30 1

Fig.9. Hypothetical “standard curve” of absorbanceversus MnO content used in spectrophotometry. Wave length 525 mp; volume 50 ml; 1 cm cell.

I-cm cell usinga spectrophotometerwith thewave-length set at 525 mp. Compare the absorbance of the sample solution with a standa’rd curve prepared by treating aliquots of a standard manganese solution in a similar manner. Preparation of standard curve (Fig.9). A standard manganese solution may be prepared by dissolving 0.11 14 g of potassium permanganate in 1 1 of water containing 5 ml of 10% w/v hydroxylamine hydrochloride solution. Of this solution 1 ml will then contain 0.05 mg of manganese as MnO. Place at least six aliquots of the standard manganese solution ranging from 0.05-0.5 mg in beakers, adjust the volume to approximately 30 ml with water, and oxidize as described above using the same additions of reagents. Allow the solutions to cool to room temperature, transfer to 50-ml volumetric flasks, and adjust to volume. Construct a curve relating absorbance against milligrams of manganese per 50 ml of solution. Note: Inasmuch as the precipitation of manganese as a hydroxide is not always completed in the Rz03 precipitation, the residual must be measured at a later stage, i.e., in the magnesium pyrophosphate precipitate; see the section on the magnesium-gravimetric method. Where E.D.T.A. titrations are to be used for the determination of calcium and magnesium, an aliquot of the filtrate from the Rz03 separation must be evaporated to dryness with 1 ml of sulphuric acid to expel chlorides before applying the above method. Determination of titanium Titanium forms a yellow complex with tiron (1 ,Zdihydroxy-benzene 3,5-disulphonic acid) (YOEand ARMSTRONG, 1947), which is more sensitive than the yellow titanium peroxide complex commonly used in rock analysis. A buffer is added to adjust the p H of the solution, as the maximum absorbance is obtained at pH 5.0. Any ferric iron present in the solution forms a purple complex with the reagent;

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and for this reason a few milligrams of sodium dithionite are added to reduce the iron to the ferrous state, in which the iron-tiron complex is colorless. Inasmuch as sodium dithionite decomposes fairly rapidly liberating colloidal sulphur, the absorbance of the solution is measured within 15 min of being prepared and compared with a standard titanium curve. An aliquot containing 0.01-0.1 mg of titanium as Ti02 is placed in a 50-ml beaker and the volume adjusted accurately to 5 ml with water. It is usually convenient initially to use a 5-ml aliquot. Add approximately 100 mg of tiron followed by 25 ml of buffer solution. The buffer solution is prepared by dissolving 40 g of ammonium acetate in about 500 ml of water, adding 15 ml of glacial acetic acid and adjusting the volume to 1 1 with water. If a purple color is present, add 10-20 mg of sodium dithionite to reduce the iron present in the solution to the colorless ferrous state. Where the iron content of the sample is high (> lo%), e.g., in siderite, the iron may interfere by the mechanism of air-reoxidation of the iron-tiron complex. In this case the iron present in the aliquot may be held as the colorless ferrous E.D.T.A. complex which does not undergo air-reoxidation (EASTON and GREENLAND,1963). Measure the absorbance of the solution against water in a 1-cm cell using a spectrophotometer with the wave-length set at 430 mp. Compare the absorbance of the sample solution with a standard curve prepared by treating aliquots of a standard titanium solution in a similar manner. Preparation of standard curve (Fig.10). A standard titanium solution may be prepared by fusing 0.02 g of pure titanium dioxide with 2 g of potassium bisulphate in a platinum crucible. After allowing the crucible to cool, the fusion cake is dissolved from the platinum crucible with 3% v/v sulphuric acid by heating until a clear solution is obtained. The volume is then adjusted to 1 1 with 1 % v/v sulphuric acid; thus 1 ml will contain 0.02 mg of titanium as TiO2. Place at least six aliquots of the standard titanium solution ranging from 0.02-0.1 mg in 100-ml beakers, and buffer solutions as before. After measuring the absorbances, construct a curve relating absorbance against milligrams of titanium in each beaker. Determination of chromium The chromium (0.02-0.1 mg Crz03) in an aliquot is oxidized by the addition of ammonium persulphate and silver nitrate (catalyst). The iron is separated by neutralizing the solution with solid sodium carbonate, the precipitate is centrifuged off and discarded. The solution is acidified with sulphuric acid and an excess of 1 ml is added. Then 10 ml of 0.1 % w/v diphenylcarbazide solution (in acetone) is added forming a pink complex with the chromate (VANDER WALTand VANDER MERWE, 1938).The absorbance is measured at a wave-length of 540mp andcompared

303

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0.6

0

Ti02 (mg)

Fig. 10. Hypothetical “standard curve” of absorbanceversus Ti02 content used in spectrophotometry. Wave length 430 mp; volume as given; 1 cm cell. Fig.11. Hypothetical “standard curve”ofabsorbance versus Crz03 content used in spectrophotometry. Wave length 540 mp; volume 50 ml; 1 cm cell.

with a standard chromium curve prepared from potassium dichromate (Fig.11). Note: Manganese present as permanganate interferes with the reaction between chromium and diphenylcarbazide (A. J. EASTON, 1964); and if present, it may be reduced by the addition of E.D.T.A. solution before the chromium-diphenylcarbazide complex is formed. A 0.1 % w/v E.D.T.A. solution is added dropwise into the flask until the permanganate color is almost discharged in the sample solution. If no permanganate color is present in the solution, this addition is omitted. Determination of phosphorus The phosphorus in the aliquot combines with the vanadomolybdate reagent to form yellow vanadomolybdic phosphoric acid (KITSONand MELLON,1944). Inasmuch as the reagent solution itself has an absorbance at 430 mp, the absorbance of the sample solution is measured against a reagent blank so that the difference in absorbance is due only to the complex formed by the phosphorus. This difference in absorbance is then compared with a standard phosphorus curve. An aliquot containing 0.01-0.3 mg of phosphorus as Pz05 is placed in a 50-ml volumetric flask and the vohme adjusted with water to approximately 15 ml. Where the phosphorus content is low, a 15-ml aliquot may be taken initially. Add 10 ml of vanadomolybdate solution. Prepare the reagent solution by dissolving 1.25 g of ammonium metavanadate (NH4V03) in 400 ml of cool 50% v/v nitric acid. Separately dissolve 50 g of ammonium molybdate in 400 ml of water and filter off any solid particles that may remain. Add the ammonium molybdate solution to the ammonium metavanadate solution and adjust the volume to 1 1. Adjust the volume to 50 ml with water and shake well to ensure complete mixing. Measure the absorbance of the solution after 5 min against the reagent

[!L

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K. H. WOLF, A. J. EASTON AND

S. WARNE

0.15

a 0.05

a

0

0.15

0.3

P205 (mg)

Fig.12. Hypothetical “standard curve” of absorbanceversus PZOScontent used in spectrophotometry. Wave length 430 my; volume 50 ml; 1 cm cell.

blank in a 1-cm cell, using a spectrophotometer with the wave-length set at 430 mp. The reagent blank is prepared by adding 10 ml of vanadomolybdate solution to a 50-ml volumetric flask and then adjusting the volume with water. Compare the absorbance of the sample solution with a standard curve prepared by treating aliquots of a standard phosphorus solution in a similar manner. Preparation of standard curve (Fig.12). A standard phosphorus solution may be prepared by dissolving a quantity of a standard phosphate rock (e.g., National Bureau of Standards phosphate rock 56) by adding 25 ml of 50% v/v nitric acid to the weighed material in a 150-ml beaker. The beaker is covered with a watch glass and the contents allowed to digest for several hours on a steam bath until the material is dissolved. A suitable concentration of the standard solution is 0.02 mg of phosphorus as PzO5 per 1 ml. Dilute solutions of phosphorus should not be stored in polyethylene bottles due to absorption of phosphorus by the walls of the container. Note: If the phosphorus content of the sample is sufficiently high so that it will not be completely precipitated with the Rz03 group, then it will remain in the filtrate. In this case it will be necessary to add a small quantity of aluminum chloride to the acidified filtrate, and then precipitate the aluminum phosphate by the addition of ammonium hydroxide as in the normal precipitation of the Rz03 group described above. The precipitate is washed free of calcium and magnesium salts by 1 % w/v ammonium nitrate solution, and then dissolved in warm 3 % v/v sulphuric acid. The solution is next transferred to a volumetric flask (e.g., 50-ml). An aliquot is then taken and the phosphorus determined with vanadomolybdate solution as given above. Determination of alurninum For the determination of aluminum two main methods are available: ( I ) gravimetric, and (2) titration with E.D.T.A. (BISQUE and LEMISH,1959). Other methods

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include a spectrophotometric measurement after extraction of aluminum oxinate (RILEYand WILLIAMS, 1959b). If a scheme of analysis has been used that requires the separation of the Rz03 group (i.e., Fig.7 left), then the aluminum may be determined by subtraction of the other constituents from the total Rs03 content. This method is usually referred to as “by difference”. An alternative method is that of titration with E.D.T.A., which may be used when the scheme shown in Fig.7 (right) has been applied to the sample. Gravimetric method “by difference”. When using this method certain considerations must be taken into account. First, the oxides are present in the ignited Rz03 group in the following form: Fez03, TiOs, Mns03, Cr203, phosphorus chiefly as AlP04, and excess aluminum as A1203. MnsOa is calculated from manganese determined as MnO by multiplying by a factor of 1.11; whereas P04. by multiplying the PzO5 found by a factor of 1.35. The second consideration is that where aluminum is a minor constituent of the RzO3 group, the magnitude of the errors involved in the determination of the other constituents may impair the accuracy of the determination of aluminum. Where this is the case and iron is the major constituent, e.g., siderite-bearing samples, the iron may be separated by an ion-exchange technique which leaves the iron retained on the column whereas the other constituents are elutriated (EASTON and LOVERING, 1963). The advantage of this separation is that the aluminum is then obtained as a relatively major constituent, and, therefore, is determined with increased accuracy. Determination of calcium Two wet chemical methods are available for the determination of calcium: (I) gravimetric precipitation as calcium oxalate followed by ignition to calcium oxide; and (2) titration with E.D.T.A. The latter method has the advantage of being a rapid procedure. A third useful physicochemical method for the determination of the MgO and CaO has been described by CHILINGAR and TERRY(1954). The sample is heated in a micro-crucible at a constant rate in a current of COz and the temperature -weight relationship is determined; from this the MgO and CaO contents can be calculated. Calcium gravimetric method (GROVES,1951). Add sufficient water to the filtrate obtained earlier from the Rz03 group precipitation (p.298) so that the volume is approximately 250 ml, contained in a 600-ml beaker, and heat to boiling after acidifying with a few drops of hydrochloric acid. While boiling add 10 ml of 5 % w/v ammonium oxalate solution and one or two drops of universal indicator. Add ammonium hydroxide dropwise until the indicator changes from red to blue;

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continue boiling for 10-20 min. The presence of a boiling stick assists in the prevention of bumping. Set the beaker aside on a water bath for 1-2 h, and then allow to remain cold for 4-5 h to ensure complete precipitation of the calcium oxalate. Filter off the precipitate through a 540 Whatman filter paper and wash the precipitate with 1 % w/v ammonium oxalate solution three or four times. Dissolve the precipitate back into the original beaker with hydrochloric acid and wash the filter paper with hot water. Reprecipitate the calcium oxalate after adjusting the volume again to 250 ml and adding 5 ml of the ammonium oxalate, by the addition of ammonium hydroxide as before. (The second precipitation being made in a nearly salt-free solution avoids the coprecipitation of other ions, e.g., Mg.) After boiling for 10 min, the precipitate is again set aside as before. The precipitate is filtered through a 540 Whatman filter paper and washed with 1 % w/v ammonium oxalate solution. The precipitate is ignited in a weighed platinum crucible, initially at a low temperature and finally at 1,100"C. After cooling in a desiccator for 30 min, the calcium is weighed as the oxide. The ignition is repeated until a constant weight is obtained. Note: The precipitate also contains SrO; thus an adjustment is made after measurement of strontium by the flame photometry method. Calcium titration method (PATTONand REEDER,1956) Transfer the combined filtrate obtained earlier from the Rz03 group precipitation (p.298) to a volumetric flask, e.g., 250 ml, and adjust to volume with water. Shake well to ensure complete mixing. Place an aliquot containing approximately 25 mg of calcium as CaO in a 250-ml beaker. Add 10 ml of concentrated nitric acid and evaporate to dryness on a steam bath to remove the ammonium salts. Rinse down the sides of the beaker, add 2 ml of nitric acid, and evaporate again. Take up the residue with approximately 50 ml of water and transfer to a 250-ml conical flask. Add 10 ml of a 10% w/v sodium hydroxide solution (pH should be ~ 1 2 )and , a few milligrams of both sodium cyanide and hydroxylamine hydrochloride. Stopper the flask and set aside for 1 h. Any magnesium present will precipitate as magnesium hydroxide. After the period of standing, add a few milligrams of Patton and Reeders acid]. This reagent [2-hydroxy-1 (-2 hydroxy-4-sulpho-l-naphthylazo)-3-naphthoic reagent is usually diluted: 0.0375 g with 20 g of sodium chloride. Then titrate with 1 % w/v E.D.T.A. (disodium salt) until the indicator changes from red to a clear sky blue color. The E.D.T.A. solution is standardized against a standard calcium solution prepared from calcium oxide obtained by heating A.R. calcium carbonate to 1,OOO"C for 1 h and then cooling in a desiccator for 30 min. Dissolve 1 g of the freshly ignited CaO in 100 ml of 5 % v/v hydrochloric acid and dilute to 1 1 with

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water; then each 1 ml will contain 1 mg of calcium as CaO. Use 25-ml portions of the standard calcium solution to standardize the E.D.T.A. solution. Determination of magnesium Two methods are available for the determination of magnesium: (I) gravimetric precipitation as magnesium pyrophosphatel, and (2) titration with E.D.T.A. Where magnesium carbonate is only a minor constituent, e.g., a fraction of 1 % as in some limestones, the titration method is preferred. Magnesium gravimetric method (GROVES, 1951). Adjust the volume of the two filtrates obtained earlier from the calcium precipitation (see the section on the calcium titration method) to approximately 800 ml in a 1-1 beaker. Make the solution just acid with a few drops of hydrochloric acid and add several drops of universal indicator. Add 10 ml 10% w/v ammonium phosphate solution and stir to mix. Add ammonium hydroxide dropwise stirring vigorously until the magnesium pyrophosphate precipitate just appears. Cease the addition of ammonium hydroxide and stir vigorously for several minutes. The slow precipitation ensures a coarse crystalline precipitate. Continue the addition of ammonium hydroxide until the indicator turns purple (pH 11), then add excess ammonium hydroxide, 5 ml for each 100 ml of solution, and set aside overnight. Filter through a 540 Whatman filter paper and wash the precipitate with 5 % v/v ammonium hydroxide solution three or four times. Dissolve the precipitate into the original beaker with 25% v/v hydrochloric acid, washing the filter paper well with 200-300 ml of water. Add 5 ml more of 10% w/v ammoniumphosphate solution and several drops of universal indicator. Reprecipitate as before after adjusting the volume to approximately 800 ml. Filter and wash the precipitate as before and ignite in a weighed platinum crucible. Care should be taken during the filtration of the magnesium pyrophosphate that the surface of the glass funnel above the filter paper remains dry. If this is not the case, the precipitate will tend to creep up the glass. This may be counteracted by washing particles down into the filter paper with ethyl alcohol. The precipitate should be ignited at a minimum temperature with free access of air to avoid reduction of the phosphate. Then the temperature should be raised slowly until it reaches approximately 1,OOO"C. The crucible is allowed to cool in a desiccator for 30 min before weighing. It is ignited again until a constant weight is obtained. Inasmuch as there is a possibility that manganese will not completely precipitate with the R203 group, the magnesium pyrophosphate precipitate is examined for manganese. Actually magnesium ammonium phosphate is the precipitate, and magnesium pyrophosphate is the result of ignition.

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Examination of precipitate for manganese. The ignited precipitate is dissolved in 5 ml 15 % v/v sulphuric acid and the solution transferred to a volumetric flask (e.g., 50 ml). Either the whole solution or an aliquot is taken and the manganese is determined as permanganate by the procedure given under the analysis of the R2O3 group. The weight of this manganese is added to that previously found in the R203 group. The weight of manganese determined as MnO is converted to Mn2P207; on using a factor of 2 before deduction from the weight of the magnesium as MgzPz07; 0.3621 * MgzPz07 = MgO. Magnesium titration method (CHENGet al., 1952). Transfer the two filtrates from the RzO3 group precipitation to a volumetric flask (e.g., 250-ml) and adjust to volume with water. Shake well to ensure complete mixing. Place an aliquot containing approximately 25 mg of magnesium as MgO in a 250-ml beaker and acidify with hydrochloric acid. Then add 5 ml of 5 % w/v ammonium oxalate solution to precipitate the calcium present, and while the solution is gently boiling neutralize with ammonium hydroxide solution and add 2-3 ml in excess. After boiling for 10 min, allow the beaker to cool and stand for 2 h; then filter off the precipitated calcium oxalate through a 540 Whatman filter paper into a 250-ml conical flask. Test the filtrate for completeness of precipitation of the calcium by adding one or two drops of 5 % w/v ammonium oxalate to the solution. Upon warming, no turbidity should develop if the precipitation is complete. If a turbidity does develop, add 5 ml more of the ammonium oxalate solution and boil, allow to stand and filter as before. Heat the solution almost to boiling and add one or two drops of 10% w/v hydroxylamine hydrochloride solution to reduce any manganese present. Then add 10 ml of ammonium hydroxide buffer (to 60 g of NH4CI dissolved in 200 ml of water, add 570 ml of ammonium hydroxide and dilute to 1 I). Add 1-2 ml of solochrome black (eriochrome black) solution (0.2 g of reagent dissolved in 50 ml of ethyl alcohol) and titrate with 1 % w/v E.D.T.A. (disodiumsalt) solution until the indicator changes from red to clear sky blue color. The E.D.T.A. solution is standardized against a standard magnesium solution prepared from magnesium oxide. The latter is obtained by heating A.R. magnesium carbonate to 1,OOO"C for 1 h and then cooling in a desiccator for 30 min. Dissolve 1 g of the freshly ignited MgO in 5 ml of hydrochloric acid and dilute to 1 1 with water; then each 1 ml will contain 1 mg of magnesium as MgO. Use 25-ml portions of the standard magnesium solution to standardize the E.D.T.A. solution.

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

309

Determination of ferrous iron Apparatus. Fit a 250-ml conical flask with a tight-fitting rubber stopper in which three holes have been bored. To two holes fit a piece of glass tubing bent at right angles. One is for the entry of an oxygen-free inert gas, e.g., COz, Nz. To the second attach a Bunsen valve to allow exit of the gas. Place a thistle funnel with a stopcock capable of holding 20 ml of acid in the third hole. Method. The sample is dissolved in hydrochloric acid in the absence of oxygen so that the ferrous iron present in the sample remains in the reduced state. 2,2'dipyridyl solution is added and forms a sufficiently strong complex with the ferrous iron to avoid oxidation during the removal of the insoluble material by filtration. Weigh out a quantity of the sample which will contain 0.05-0.5 mg of iron calculated from the total iron determination (see above). If the iron content is high, the quantity to be taken should be such that a ten-fold dilution after solution of the sample will bring it to within this range. Transfer the weighed material to the conical flask and add 20 ml of water; then swirl the contents carefully to wet the sample. Connect the inert gas supply and allow it to pass through the flask for 5-10 min to expel the air. Add 10 ml of 10% v/v hydrochloric acid to the thistle funnel, depress the Bunsen valve and slowly add the acid to the contents of the flask. After the vigorous reaction has finished, release the Bunsen valve to its normal position and warm on a water bath to 50-60°C for 30 min to complete the reaction. After this period, allow the flask to cool to room temperature either naturally or by cooling in a trough of cold water. Disconnect the gas supply and immediately add 10 ml of 0.2% w/v 2,2'dipyridyl solution (prepared in 1.5 % v/v hydrochloric acid). Filter the solution through a previously water-washed 541 Whatman filter paper into a 100-ml volumetric flask, washing the sides of the conical flask with small portions of water. Wash the residue several times with small portions of water. If a maximum of 0.5 mg of iron has been calculated to be present, add 25 ml of sodium acetate buffer (272 g CHsCOONa.3HzO per liter) and adjust the volume to 100 ml with water. If 5.0 mg of iron has been calculated to be present in the solution, adjust the volume to 100 ml, mix well and pipette a 10-ml aliquot of this solution into another 100-ml volumetric flask. To this flask add 5 ml of 0.2 % w/v 2,2'-dipyridyl solution and 25 ml of sodium acetate buffer, and adjust to 100 ml with water. Measure the absorbance of the solution against water in a 1-cm cell using a spectrophotometer with the wave-length set at 522 mp.Compare the absorbance of the sample solution with a standard curve (Fig.l3), which may be calculated from the curve prepared for the determination of total iron (see above). The ferric iron is calculated by converting the FeO value to Fez03 and sub-

3 10

K . H. WOLF, A. J. EASTON AND S. WARNE

0.6

“c 01

0.3 0 n u)

a

0

Fig. 13. Hypothetical “standard curve” of absorbanceversus FeO content used in spectrophotometry. Wave length 522 mp; volume 100 ml; I cm cell.

tracting this from the total iron taken as Fez03; the difference is the amount of ferric iron, i.e., Fez03 (0.9 * Fez03 = FeO). Determination of sodium, potassium and strontium

The determination of these elements by flame-photometry requires the measurement of the radiation emitted by these elements from a solution excited by a flame (DEAN,1960). The sample solution is drawn up in a finely divided state into a flame, and the resulting radiation compared with that given by standard solutions under the same conditions. A number of combinations of flame condition and instrument are available. The details given here are for a Beckman flame-photometric attachment, but the procedures for measurement of background and elimination of interferences are generally applicable. Interferences. The main interfering ions in the determination of sodium and potassium are the members of the RzO3 group, i.e., Fe, Al, and the elements Ca and Mg. The interfering elements emit their own characteristic radiation which interferes with that of the alkalies, e.g., Fe and Ca. The other type of interference is a depression ofthe radiation, and this is exhibited by A1 and Mg. It is for this reason that the Rz03 group and calcium are separated before the measurement of the alkalies in the flame. In the case of strontium only, the Rz03 group is removed (DIAMOND, 1955); the precipitation of calcium would also precipitate the strontium as oxalate. The interference caused by magnesium is eliminated by the use of standard addition technique, provided the background radiation is first deducted. Background. When small quantities ( < O . 1 %) of sodium and potassium (also 1964), a large slit width is restrontium) are measured (EASTONand LOVERING, quired which will allow extraneous radiation also to be measured. This radiation,

31 1

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

72 5

768 Potassium

825

Fig.14. Curve constructed to determine both the background and peak heights of each sample and standard; examplified here by potassium. The relevant wave lengths for each element are given in Table VII. In all subsequent measurements, used for obtaining either an approximate value (Fig.15) or for the standard addition technique (Fig.l6), the background is deducted leaving only the peak height to be plotted. (Wave lengths in mp.)

which is not associated with the radiation from the elements to be measured, is known as background (Fig.14). In the case of potassium it is necessary to take readings of the background at both 725 and 825 mp and calculate graphically the background at 768 mp. The wave lengths for the measurement of the peak and background radiation are given in Table VII.

Preparation of the sample solution for sodium and potassium. Weigh 0.5 g of the sample into a 250-ml beaker, add 25 ml of water followed by 10 ml of 50% v/v hydrochloric acid, and place the beaker on a water bath for 30 min to allow complete solution of the carbonate portion of the sample. Wash the cover glass into the beaker and add 1 g of A.R. oxalic acid; heat gently at first to dissolve the sample and then heat almost to boiling. Pass ammonia vapor through the solution until the solution is neutral to Universal indicator paper. This will precipitate the RzO3 group components as hydroxides and the calcium as calcium oxalate. The passage of compressed air through a wash bottle containing ammonium hydroxide (s.g. = 0.88) is a convenient method of obtaining the ammonia vapor for the neutralization. After neutralizing the solution, stand the beaker on a steam bath for 10 min to complete precipitation. TABLE VII WAVE LENGTHS FOR THE MEASUREMENT OF RADIATION

peak background

(mp)

Na

K

Sr

588 580 or 600

768 125 and 825

46 1 466

312

K. H. WOLF, A. J. EASTON AND S. WARNE

The precipitated hydroxides and calcium oxalate are centrifuged off using clean glass tubes. The supernatant liquid is collected in a 50-ml volumetric flask, I .5 ml of hydrochloric acid is added and the solution is allowed to cool before being adjusted to volume with water. This solution is set aside for measurement of the amounts of sodium and potassium. A blank is prepared by using the same quantity of reagents as above. Preparation of sample solutionfor strontium. Weigh 0.5 g of the sample into a 250-ml beaker, add 25 ml of water followed by 10 ml of 50% v/v hydrochloric acid, and place the beaker on a water bath for 30 min to allow complete solution of the carbonate portion of the sample. Wash the cover glass into the beaker. Pass ammonia vapor through the solution until the solution is neutral to universal indicator paper. After neutralizing the solution, stand the beaker on a steam bath for 10 min to complete precipitation. The precipitated hydroxides are centrifuged off using clean glass tubes. The supernatant liquid is collected in a 50-ml volumetric flask, 1.5 ml of hydrochloric acid is added and the solution is allowed to cool before being adjusted to volume with water. This solution is set aside for the measurement of strontium. Preparation of standard solutions. Weigh 2.54 g of dried A.R. sodium chloride (for Na standard), 1.91 g of dried A.R. potassium chloride (for K standard), and 1.685 g of dried A.R. strontium carbonate (for Sr standard) into three separate 100-ml beakers. Dissolve the material in 20-50 ml of water (add a minimum of HCI for the SrC03) and transfer the solutions to three 1-1flasks; then make up to volume with 1 % v/v hydrochloric acid. The concentration of Na, K and Sr in these solutions is 1,OOO p.p.m. These solutions are then diluted with 1 % v/v hydrochloric acid to the required range of concentrations: this will usually be 1-10 and 10-100 p.p.m; (0.1-1.0 for the blank).

I

Concentration (ppm. Na, K or S r )

Fig.15. Curve constructed from four standards such that the radiation given by the sample lies within the range covered by that of the standards. The background has been deducted in each case prior to plotting. The approximate concentration (in p.p.m.) of the element in the solution is obtained by reference to the horizontal axis. This approximate value is used as a guide to the strength of the standard solutions required when using the “standard addition” technique (see Fig. 16).

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

313

Measurement of approximate value. First, an approximate value is obtained by direct comparison with standards both above and below the transmission given by the sample. Turn the wave-length dial to the peak transmission for the element and adjust the slit width so that the highest standard selected gives a high transmission reading, e.g., 80-90 %. Now place the standards and sample solution alternately in the flame, repeating the operation until constant readings are obtained and the sample solution has been bracketed by standards. Record these readings and repeat the operation for the same solutions, with the dial turned to the background wave-lengths to obtain readings on any background present. Subtract the background from the readings and use the peak heights to obtain an approximate value (Fig.15). Deduct the appropriate blanks. Measurement by standard addition. Having obtained an approximate value of the content by the procedure given above, place 5-ml aliquots of the sample solution in four 25-ml beakers. To the first beaker add 5 ml of water and to the other three add 5 ml of standard solutions, so that the first addition is equal in parts per million to the previously found approximate value. The others are of higher concentrations. Swirl to mix the four solutions and then place them in succession in the flame with the wave-length dial turned to the peak wave-length. Record the transmission. Repeat the operation with the wave-length dial turned to the background wavelength to obtain readings of any background present. If a background is present, subtract this from the former readings. These results are now plotted graphically as shown in Fig.16, and the line joining the points is projected back to the base line from which the concentration of the unknown sample solution is read. Determination of total sulphur (A. I. VOGEL,1951)

Weigh up to 25 g of the sample into a 400-ml beaker and add 100 ml of saturated bromine water; stir to ensure complete wetting of the sample. Add nitric acid dropwise until the sample is dissolved. A violent reaction should be avoided because loss of HzS will cause a low result. After solution of the sample, gently heat the solution to discharge the excess bromine. After the bulk of the bromine has been discharged, filter off any insoluble residue through a 541 Whatman filter paper. Wash the residue three or four times with hot water. Add 10 ml of hydrochloric acid to the filtrate and evaporate to dryness on a water bath to discharge the nitric acid. Take up the residue in 250 ml of hot water and heat to boiling. Remove the beaker from the heater and add 10 ml of hydrochloric acid to make the solution acid (0.5 N). Slowly add 10 ml of hot 5 % w/v barium chloride

314

Content

K. H. WOLF, A. J. EASTON AND S. WARNE

0 Addition (ppm. Na,K or Sr)

Fig.16. Curve constructed to determine the exact concentration by “standard addition”. Point I, indicating the lowest percentage of transmission, represents 5 ml of the unknown sample (whose concentration has been determined approximately) plus 5 ml of water. Point 2: 5 ml of the unknown sample plus 5 ml of a standard of about the same concentration as the approximate value of the unknown sample. Point 3: 5 ml of unknown sample plus 5 ml of a standard having 50% higher concentration than that used for point 2. Point 4, indicating the highest percentage of transmission, represents 5 ml of unknown sample plus 5 ml of a standard having 100% higher concentration than that used for point 2. In all cases the background has been deducted and the peak heights plotted. Point 0 indicates zero addition only and is not to be confused with “zero content” which lies farther to the left on the horizontal axis. p.p.m. x 50 = weight in micrograms of the element; weight of the element in grams x 100 divided by the weight of the sample gives the percentage.

solution, stirring continuously. Allow the beaker to stand on a water bath for 2 h, filter precipitate through a 540 Whatman filter paper, and wash with small portions of cold water. Continue the washings until the filtrate is free from chloride, as shown by allowing a few drops of the filtrate to collect in a test tube containing 1-2 ml of 1 % w/v silver-nitrate solution. Ignite the precipitate in a previously weighed platinum crucible, allowing free access of air to avoid reduction of the barium sulphate. Continue ignition until a constant weight is obtained. Calculate the sulphur content of the sample from the weight of the ignited BaS04: 0.13735 * Bas04 = S Determination of sukhur trioxide (NATIONAL BUREAUOF STANDARD METHODS, 1928). Weigh up to 25 g of the sample into a 400-mlbeaker and add dilute 50 % v/v hydrochloric acid until the sample is dissolved. Then add additional 10 ml of acid and evaporate the solution nearly to dryness. This will discharge any sulphide present in the sample, leaving sulphate ions in the residue. Increase the volume to 250 ml with hot water and filter off any insoluble residue through a 541 Whatman filter paper; wash the residue three or four times with hot water. Heat the solution to boiling. Precipitate the sulphate, filter and ignite the precipitate as described above for the determination of total sulphur.

315

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

Chlorine (A. I. VOGEL,1951)

The chloride ions present in the neutral sample solution are titrated with silvernitrate solution. In the presence of a slight excess of silver ions, a red coloration, (i.e., silver chromate) is formed indicating the end point of the titration. The surface of the sample should be cleaned with dilute 5 % v/v nitric acid. Weigh 2-5 g of the sample into a 250-ml beaker and add sufficient nitric acid under a cover glass to dissolve the sample. Warm until the reaction has ceased, then filter through a 541 Whatman filter paper. Evaporate the filtrate to dryness on a water bath and bake for 1 h to expel any excess nitric acid present. Dissolve the residue in 100 ml of water and transfer the solution to a 250-ml conical flask. Check by the use of Universal indicator paper that the solution is neutral and add a small excess of A.R. ammonium acetate in the solid form. Add 1 ml of 2.5% v/v potassium-chromate solution as indicator and titrate with silver nitrate solution (1.699 g AgN03/1). The end point is indicated by the formation of deep-red silver chromate. 1 ml of silver nitrate solution = 0.0003546 g CI.

DIFFERENTIAL THERMAL ANALYSIS

The use of differential thermal analysis (D.T.A.) equipment is now routine in petrological and mineralogical laboratories. This technique is widely used for carbonate minerals and rock studies. The latest equipment, once loaded with the test sample and switched on, will continuously record the endothermic and exothermic data as a thermogram at preset heating rate, sensitivity and furnace atmosphere conditions. Carbonate minerals considered here are classified in Table VIII. For reference, thermograms characteristic of these carbonates, obtained from specimens of known chemical composition, are given in Table IX. These were determined from material crushed to -150 mesh (B.S.S.), heated at lSoC/ min, while the furnace atmospheres other than air were maintained by a 2 I/min TABLE VIII CLASSIFICATION OF SOME CARBONATE MINERALS

Calcite group

Aragonite group

Dolomite group

siderite magnesite calcite

aragonite witherite strontianite

dolomite ankerite

316

K. H. WOLF, A. J. EASTON AND S. WARNE

TABLE IX CHEMICAL ANALYSIS OF SOME CARBONATE MINERALS'

Mineral

CaCO3 Mgc03 FeCO3 MnCO3 BaCO3 SrCO3 Bas04 SiOz

ankerite calcite dolomite magnesite siderite witherite strontianite

51.63 98.70 50.82

-

1.46 0.70 7.60

19.05

28.23 0.48 5.52 0.96 81.86

trace

39.33 99.40 9.50

-

-

1.09

trace 6.38

-

-

-

95.57

-

-

-

0.07

-

-

-

-

0.48

0.10

-

2.16 92.42

Fez03

1.61

-

-

4.33

-

-

-

-

Total

f %I

100.07 99.18 100.00 100.36 99.78 100.04 100.02

1 The D.T.A. and T.G.A. curves of the listed minerals are given in this chapter. These analyses were generously provided by the Western Australian Government Chemical Laboratories, the New South Wales Department of Mines, and the School of Applied Geology, University of New South Wales.

of a particular gas flow. This, together with the apparatus used, has been described elsewhere (WARNE,1964). BECK (1950), WEBBand HEYSTEK(1957) and SMYKATZ-KLOSS (1964) provided D.T.A. data on less common carbonates; whereas the marked influence on thermogram configuration of controllable variables, and specifically crystallinity, (1 962) and BAYLISS(1964). has been described respectively by BAYLISSand WARNE

Calcite group1 Siderite (FeCO3) The thermogram of siderite determined in air is characterized by a single endothermic peak Ed./ (sometimes preceded by a small exothermic peak: Ex.I), which is followed by two exothermic peaks Ex.2 and Ex.3 (Fig. 17, curve 13). The peak temperatures occur at approximately 520", 590", 675 " and 850°C. The conflicting published decomposition mechanisms of siderite were reviewed by WARNE(1961), from which it would appear that the decomposition mechanism described by KULPet al. (1951) is the most acceptable. It involves three reactions:

+

(I) FeCOa-tFeO COz? (2) 2Fe0 O+a-Fez03 y-Fez03 (3) y-Fez03-ta-Fez03

+

+

endothermic (Ed./) exothermic (Ex.2) exothermic (Ex..?)

For the D.T.A. of rhodochrosite (MnC03) and smithsonite (ZnCOa), see KissiNGER et al.

(1956) and WEBBand HEYSTEK (1957), respectively.

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

317

The small exothermic peak, Ex.1, has been attributed (PAPAILHAU, 1958) to the immediate oxidation of the FeO released during the initial slow decomposition of FeC03. After a small increase in temperature, however, the endothermic decomposition rate rapidly increases and becomes dominant (Ed.I). The major exothermic peak, Ex.2, is generally partially superimposed on the preceding endothermic peak, Ed.1, which consequently shows some size reduction. When determined in COz or inert gases, the thermogram is composed solely of the fully developed endothermic peak, Ed.1, caused by the reaction I given above (Fig.17, curve 12). In Nz and COz the thermograms are similar, except that the commencement of the reaction and its peak temperature occur at slightly higher temperatures in COe. The second reaction probably occurs because the end product is magnetite (Fe304) (cf. KISSINGER et al., 1956). The reaction rate must be slow and uniform as no additional recognizable peak is recorded: 3Fe0

+ COz+Fe304 + CO f

SCHWOB(1950) indicated that such a reaction was possible, and the slow oxidation of FeO, liberated by the D.T.A. of siderite in nitrogen, has been attributed to the same reaction (CAILL~RE, 1962). Under closely reproducible conditions, the detection limits and the effects on thermogram configuration of many carbonate minerals, caused by progressive artificial dilution with alundum, have been determined (WARNE,1963). The detection limits for siderite were between 2 5 5 % and 1-2% when determined in air and Nz, respectively. When determined in air, the thermogram shows a major modification for siderite contents between 30 and 40 % (by weight). Here, the increasing diminution of the endothermic peak, Ed.Z, becomes very marked; this gradually occurs with decreasing siderite content due to the progressive superposition of the stronger exothermic peak, Ex.2 (Fig. 17). At about 30 % siderite content, the resultant thermogram contains only a relatively small exothermic peak, because the exothermic peak, Ex.3, has become too weak to be recorded. With further decreases in siderite content, this single exothermic peak is so rapidly reduced in size that below 20 % it is recorded as a relatively insignificant feature. This confirms in detail the results of ROWLAND and JONAS (1949). In 0 2 this process is accelerated. Thus, the endothermic peak is completely suppressed even when 100 % siderite is present (ROWLAND and JONAS,1949; PAPAILHAU, 1958, 1959). The same effect was obtained by finely grinding the sample before D.T.A. analysis (ROWLAND and JONAS,1949). Magnesite ( M g c o 3 ) The available literature on magnesite D.T.A. is listed by SCHWOB (1950), WARNE (1962) SMYKATZ-KLOSS (1964). The D.T.A. and decomposition mechanisms of rhodochrosite have been described in detail by KULPet al. (1949) and KISSINCER

318

K . H. WOLF, A. J. EASTON AND S. WARNE

et al. (1956), and those of breunnerite and pistomesite by BECK(1950) and SCHWOB

(1 950).

The thermogram of magnesite, determined in air, is composed of a single large asymmetrical endothermic peak, due to the simple irreversible reaction: MgC03 +MgO C02 .T (SCHWOB, 1950). The peak temperature usually occurs between 660 and 700°C (Fig. 17). The additional small peaks sometimes recorded at higher temperatures (Fig.17, curve 19) have been attributed to the presence of small amounts of Ca, Feyand/or Mn. The formation of intermediate oxycarbonates as suggested by BRILL(1905) was not supported by X-ray and optical studies (BECK, 1950). The thermogram configuration is little affected by furnace atmosphere conditions (SCHWOB,1950; HAUL and HEYSTEK,1952; and WARNE,1963). The presence of only 1.xNaCl, however, lowers the peak temperature 50°C (BERG, 1943), and sharpens the initial inflection point (WEBBand HEYSTEK, 1957). The effects of progressive dilution are a gradual reduction in peak height, area, and temperature, whereas the detection limit is approximately 1% (Fig.17; WARNE, 1963).

+

Calcite (CaCO3) WEBBand HEYSTEK (1957) and WARNE (1963) have reviewed the literature on calcite D.T.A. In air or N2 the thermograms are similar, being composed of a single large asymmetrical endothermic peak caused by the reaction CaCOasCaO C02 t . The peak temperature generally occurs between 960 and 990°C. Evidence ranging from distortions to marked bifurcation of the calcite and (1950b), and aragonite endothermic peak, as figured by FAUST(1950), GRUVER WEBBand HEYSTEK (1957) has been attributed to the decomposition of two “types” of CaCO3 present: (1) primary calcite; (2) calcite formed by the inversion of aragonite. Thus, thermograms from samples containing mixtures of two calcites having markedly different crystallinity might be expected to show similar modifications. Determination in static or dynamic C02 atmospheres (ROWLAND and LEWIS, 1951; and WARNE,1963, respectively) displaces the endothermic peak up scale, thus increasing the peak temperature by about 60°C (Fig.18, curves 5 and 6). From a mixture of calcite and quartz, LIPPMAN (1952) recorded a small exothermic fluctuation due to wollastonite (CaSi03) formation, immediately following the “calcite” endothermic peak. This reaction was confirmed only when

+

Fig.17. D.T.A. curves of the major carbonates (siderite and magnesite) illustrating thermogram configuration and the effects of dilution and furnace atmosphere. Fig.18. D.T.A. curves of the major carbonates (calcite, aragonite, witherite, strontianite and dolomite) illustrating thermogram configuration and the effects of dilution and furnace atmosphere, and the difference between dolomite and a comparable mixture of magnesite plus calcite.

319 I , -2

mo

roo

mo

600

'

'

roi~c

5k5

%8

SIDERITE

30170

WLDMITE

2ibl

,9

MAGNESITE

_-------DETERMNED IN N ................. DETERMINED IN 0; 200

rpo

600

K

U

800

, lppopo'c

320

K. H. WOLF, A. J. EASTON AND S. WARNE

the constituents were very fine grained and intimately mixed (WARNE,1963). Thermograms from mixtures containing siderite or magnesite instead of calcite, contained no peaks attributable to Fe- or Mg-silicate formation. A gradual reduction in peak height, area and temperature results from progressive dilution; the detection limit is about 1 % (Fig.18; WARNE,1963). Aragonite group1 Aragonite (CaCO3) The thermograms of aragonite and calcite are similar, having a large endothermic peak caused by the same reaction: CaCOasCaO COZf . In addition, aragonite has a small endothermic peak between about 400 and 500°C due to the inversion of orthorhombic aragonite to trigonal calcite (Fig.18, curve 8). The latter small characteristic inversion peak is not detected when aragonite content is much below 35 %. This may vary considerably with the sensitivity of the D.T.A. unit used.

+

Witherite2 (BaCO3) and strontianite (SrCO3) The witherite and strontianite thermograms of CUTHBERT and ROWLAND(1947), GRUVER(1 950a), KAUFFMAN and DILLING (1 950), BARONet al. (1959), WARNE (1963), and SMYKATZ-KLOSS (1964) are in good agreement. The witherite thermogram is composed of two small sharp endothermic peaks (peak temperatures at about 820 and 980"C), due to reversible inversions from a to /l to y forms; whereas the cooling curve shows two similar exothermic peaks at somewhat lower temperatures due to y to /l to a inversions (Fig.18, curve 9). No decomposition takes place below 1,350"C. The thermogram of strontianite below 1,OOO"C is composed of a small sharp endothermic peak (approximate peak temperature is 930 "C) caused by an orthorhombic to trigonal inversion. Inasmuch as the latter is reversible, it shows as an exothermic peak on the cooling curve at about 850°C (Fig.18, curve 20). At temperatures above 1,000"C, endothermic decomposition starts, giving a peak temperature at about 1,200"C (WEBBand HEYSTEK, 1957). The presence of strontianite with calcite, endothermic peaks of which are usually superimposed, may be detected by the exothermic strontianite inversion peak on the cooling curve. If cooled in COz, however, this peak will be obscured by the recarbonation peak of calcite.

1 Cerussite has been

studied in detail by WARNE and BAYLISS (1962).

* Thermograms of bromlite, BaCa(CO&, and baryto-calcitehave been published by BECK(1950).

EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

32 1

Dolomite group' Dolomite, C a M g ( C 0 3 ) ~ The available literature on dolomite D.T.A. is listed by SCHWOB ( I 950), GABINET (1959), WARNE (1962), and SMYKATZ-KLOSS (1964). Thermograms of dolomite determined in air or nitrogen are similar, being composed of two large endothermic peaks (Fig. 18, curve 18). The peak temperatures occur at approximately 800 and 950°C. It is generally accepted that the first and second endothermic peaks are caused by the dissociation of C02 from the ions in the Mg and Ca lattice positions, respectively. The first and second dolomite peaks occur at considerably higher and slightly lower temperatures than the corresponding peaks of magnesite and calcite (BECK, 1950). This enables one to differentiate dolomite from magnesite, calcite, or their mixture (Fig.18, curve 19). For dolomite+alcite mixtures, the CaC03 decomposition peaks of both minerals are usually superimposed, but the presence of considerable proportions of calcite may be inferred from the disproportionate enlargement of the resulting peak (Fig.18, curves 16 and 17; WARNE,1964). Occasionally, incomplete superposition results in a doubly terminating feature (SMYKATZ-KLOSS, 1964).The presence of salts, although greatly affecting the initial decomposition temperature, leaves the second peak unaltered (MURRAYet al., 1951). The D.T.A. of dolomite in C02 results in lowering and raising the first and second peak temperatures, respectively; whereas the cooling curve (in C02) shows only the exothermic recarbonation peak of calcite (Fig.18, curve 15). With progressive dilution, the peak sizes, areas and temperatures gradually decrease, but the second peak temperature falls more rapidly than the first. Thus, for dolomite contents below 20 % these peaks slowly coalesce to form a single peak. This is observable down to the detection limit of about 1 X(Fig.18; WARNE,1963). Ankerite, Ca(Mg,Fe) (CO3)z Ankerite thermograms (in air) contain three endothermic peaks, with peak temperatures generally occurring between 700-800 "C, 830-870 "C, and 930-950 "C, respectively. The first peak is sometimes followed by an exothermic reaction, which suppresses the immediately preceding and following peaks to a variable degree (cf. the published thermograms by GABINET, 1959; WARNE, 1962; and SMYKATZKLOSS, 1964). The increase in size of the second endothermic peak (not the first) with increasing Fez+content, and the production of a similar peak from a calcite-hematite For thermograms of huntite, MgCa(CO&, see FAUST (1953), KOBLENCZ and NEMECZ (1953), and BARON et al. (1959). 1

322

K. H. WOLF, A. J. EASTON AND S. WARNE

mixture (KULPet a]., 1951), apparently invalidates the mechanism of BECK(1951) and SMYKATZ-KLOSS (1964). According to KULP et al. (1951), dissociation at Mg positions in the lattice causes the first peak; MgO and FeO are released, the latter oxidizing immediately to y-FezO3 (exothermic). The Fez03.CaC03 formation produces the second endothermic peak (hence the dependence of the size of this peak on Fez+ content), whereas the dissociation of C02 from the Fe203.CaC03 and residual CaC03 produces the third endothermic peak. The end products were confirmed to be MgO and CaO.FezO3. Peak temperature differences enable one to distinguish ankerite from mixtures of siderite, magnesite and calcite (the presence o f a superimposed peak of calcite may be detected as described under dolomite) (Fig.20, curves I, 2 and 3). As previously described, siderite contents below 30% are best detected by using N2 atmosphere. Progressive dilution effects are similar to those of dolomite, except that all three peaks coalesce for ankerite contents much below 20% (Fig.19). The determination in COz results in greater peak separation than shown by dolomite (Fig.19, curve 5).

ANKERITE +CALCITE (I :I)

ANKERlTE +OOLOMITE +AI2O3 (2:1:1)

-DETERMINED 200

Fig.19.

400

--

-

IN AIR SO0

Fig.20.

Fig.19. Thermograms (D.T.A.) of ankerite showing the effects of dilution and futnace atmosphere. Fig.20. Thermograms (D.T.A.) of mixtures of carbonates minerals.

EXAMINATION AND ANALYSIS OF SEDIMENTARY CARBONATES

323

Mixtures of carbonates Thermograms (in air) of bimineralic (1 : I ) artificial mixtures of the above described nine carbonates show no evidence of interaction. The effects of all carbonate peaks can be recognized even for dolomite-ankerite mixtures (Fig.20, curve 4), although superposition of some peaks does occur (WARNE,1963). Even though no detailed study of mixtures of all these carbonates in various proportions was made, it is concluded that they are detectable in mixtures by D.T.A. Detection limits should be similar to those established for the individual mineral-dilution sequences. Due to peak coalescence, the detection limits of dolomite or ankerite in mixtures may be somewhat higher. With the exception of siderite-rhodochrosite mixtures, this conclusion is supported by the limited number of studies on carbonate mixtures (KULPet al., 1949, 1951; FAUST,1953; KOBLENCZ and NEMECZ,1953; CAPDECOMME and PWLOU,1954; WEBBand HEYSTEK, 1957; and WARNE,1964). Problems arising from the confusing multiplicity of peaks exhibited by samples containing several minerals are greatly reduced by using the double D.T.A. method Of GR~MSHAW et al. (1945) or D.T.A. of artificial mixtures. Further D.T.A. data on the minerals which may occur in relatively minor amounts in carbonate rocks are presented by MACKENZIE (1957). THERMOGRAVIMETRIC ANALYSIS

Thermogravimetric analysis (T.G.A.), the continuous record of weight changes produced by heating a sample at a constant rate, is complementary to D.T.A. as it provides continuous weight variation data relatable to the D.T.A. peaks. The variations in the rate of weight change are often recorded only as lines having slightly different slopes on T.G.A. curves, also called thermobalance curves, although considerable improvement is indicated by determination in self-generating atmospheres (GARNand KESSLER,1960; GARN,1961). Simultaneous determinations of T.G.A. and D.T.A. curves are described by KISSINGER et al. (1956) and PAPAILHAU (1959). SCHWOB (1950) studied the Fe, Mg, and Ca carbonates covering the effects of NaCl, flux, and atmospheres of air, COZ and water vapor. PAPAILHAU (1959), CAILLI~RE and POBEGUIN (1960), CAILL~RE (1962), and WARNE(1963) presented additional curves. (See KISSINGER et al., 1956, and WARNEand BAYLISS,1962, for data on rhodochrosite and cerussite.) For reference, T.G.A. curves of the carbonate minerals used for D.T.A., except strontianite and witherite (the T.G.A. curve of aragonite is identical with that of calcite), are included here in Fig. 21. They were determined on using a continuously weighing Stanton thermobalance reading to 1 mg, and 1.00 g samples at - 100 mesh (B.S.S.). The heating rate was 5.5 "C/min. Diagnostically different curves are presented for: ( I ) magnesite, (2) siderite, (3) dolomite and ankerite, and (4) calcite. Although thermogravimetric studies of carbonate

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K. H. WOLF, A. J. EASTON AND S. WARNE i

"

"

"

"

"

"

"

"

"

1

TEMPERATVRE(~C)

Fig.21. Curves illustrating the T.G.A. of siderite, rnagnesite, calcite, dolomite and ankerite, the D.T.A. curves of which are shown in Fig.17-20.

mixtures have not been made, the detection of reasonable proportions of these minerals in bimineralic mixtures, with the exception of dolomite and ankerite or calcite with dolomite or ankerite, appears likely. The anticipated detection limits by T.G.A. would be considerably higher than those by D.T.A.

X-RAY DIFFRACTION

Amongst the many descriptions of the experimental methods and techniques for X-ray diffraction those of AZAROFF and BUERGER (1958), BRINDLEY (1961), and GRAFand GOLDSMITH (1963) provide a good coverage. The diffraction patterns of the carbonate and associated minerals in carbonate rocks are diagnostically different and their identification is made by reference to suitable collations of X-ray diffraction data, such as the A.S.T.M. X-ray powder data index (BROWN,1961). Data for the rhombohedra1 carbonates specifically was presented by GRAF(1961). Despite the multiplicity of diffraction lines or peaks, the constituents of mixed carbonates may be identified by various X-ray diffraction techniques. From the relative intensities of the strongest diffraction lines of dolomite and calcite (determined by diffractometer examination of fine powders in a cell type holder), their percentage contents may be read off from the calibration curve of TENNANT and BERGER (1957). This is considered to apply equally well to dolomite-

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magnesite mixtures. The adaptations to polished rock slices and plastic bonded grain mounts were described by HUGHES et al. (1960) and WEBER and SMITH(1961). The detection limit of 5 % suggested by these workers also applies to magnesite, siderite, rhodochrosite and minerals commonly associated with them which they listed; whereas albite, gypsum and polyhalite may produce interfering reflections. and LEMISH (1960) The description of a wet chemical X-ray method by HILTROP has been followed by a detailed appraisal of this and other X-ray methods previously applied to the determination of the calcite, dolomite, quartz and clay et al. (1963). For the quantitative detercontents of carbonate rocks by DIEBOLD mination of calcite, dolomite and quartz, the quantitative and qualitative evaluation of the clay mineral fraction, and the composition of calcite and dolomite, they recommended the following four procedures: ( I ) an internal standard method modelled after ALEXANDER and KLUG (1 959); (2) a subtraction method described by them; (3) clay separation and X-ray diffraction; and (4) a modified method after HARKER and TUTTLE (1955). Furthermore, the merits of both the “Tennant and Berger” and “Hiltrop and Lemish” methods were evaluated. By measuring integrated line intensity in place of peak intensity, DAVIES and HOOPER(1963) achieved a detection limit of 1 % for calcite or aragonite in mixtures of the two. The composition of individual members of the dolomite, ferroan dolomite, ankerite series can be obtained from the diffraction data of H o W l E and BROADHURST (1958) and GOLDSMITH et al. (1 962). ROSENBERG (1963) established the relationship of variation in 2 0 with composition for the systems MgC03-FeC03 and MnC03FeC03. GRAFand GOLDSMITH (1955) established the relationship between the composition of magnesian calcites and calcian dolomites and their unit-cell edges. This led to its detailed application by SKINNER (1963) and to an improved method of measurement of small changes in the lattice spacings of calcites, with particular reference to Mg2+substitution (WAITE,1963). By employing the techniques of CHAVE (1 954) and GOLDSMITH et al. (1955), TAFTand HARBAUGH (1964) constructed calibration curves from which the proportions of aragonite, low-Mg calcite and high-Mg calcite may be determined from the ratio of the intensity of their diffraction peaks. X-ray diffraction studies thus provide, within the limits described by the various authors, suitable methods for the rapid evaluation of the minerals present in carbonate rocks. Interesting to note in this regard is the observation made by GOTO (1961, p.614) that vaterite and Ca-bearing strontianite have properties that may cause them to be confused with aragonite; and, in addition, their sensitivity to chemical tests, such as Meigen’s reaction, resemble that of aragonite. HOOPER (1964) described the method of electron probe X-ray microanalysis for the determination of trace elements, as exemplified on Foraminifera, and discussed its advantages as compared to other techniques.

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THERMOLUMINESCENCE OF CARBONATES

Certain minerals such as calcite, dolomite, fluorite, and potash feldspar, for example, emit light when heated to temperatures below that of incandescence. A specimen emits this light (“thermoluminescence”) only once, and it has to be exposed to X-rays or y-rays before a second heating will produce thermoluminescence. According to DANIELS et al. (1953), natural carbonates previously exposed to 6OCo radiation show four temperature peaks: a t 120-140°, 150-190”, 210-250”, and 290-310°C. The two lower peaks are often not observed because ambient temperatures are usually high enough to cause a shift of electrons from their traps. ZELLER and PEARN(1960), however, were able to observe the 125°C peak in refrigerated Antarctic limestone specimens. For the theory that explains thermoluminescence and the experimental procedures, the reader may consult the numerous readily available publications by DANIELS et al. (1953), PARKS(1953), SAUNDERS (1 953), ZELLER (1954), BERGSTROM (1956), LEWIS(1956b), PITRAT(1956), ZELLERet al. (1957), DANIELS (1958), ANGINO and SIEGEL (1959), JOHNSON (1960), and SIEGEL (1963). In numerous instances the various investigators have suggested that thermoluminescence may be a useful tool in practical and research geology. It has been found, however, that the glow curves of carbonate sediments “represent an algebraic total of diverse physical and chemical influences” (BERGSTROM, 1956)such as: mineralogy (OCKERMAN and DANIELS, 1954; LEWIS,1956b; ZELLER and WRAY, 1956; MOORE,1957; RIEKE,1957; DANIELS, 1958; and JOHNSON, 1960), polymorphism (ZELLER and WRAY,1956; and JOHNSON, 1960), ratio of minerals present (LEWIS,1956b; PITRAT, 1956; JOHNSON, 1960; and INGERSON, 1962), trace elements or “impurities” (PITRAT,1956; ZELLERand WRAY,1956; ZELLERet al., 1957; DANIELS, 1958;and JOHNSON, 1960),exposure to radioactive material (DANIELS et al., 1953;PARKS, 1953;SAUNDERS, 1953; LEWIS,1956b; PITRAT, 1956;ZELLERetal., 1957; and DANIELS, 1999, heating (MOORE,1957; INGERSON, 1962; and MCDIARMID, 1963), pressure (ZELLERet al., 1955, 1957; DANIELS, 1958; BARNES, 1959; and INGERSON, 1962), recrystallization and inversion (MOORE,1957; ZELLERet al., 1957; DANIELS, 1958; JOHNSON, 1960; and INGERSON, 1962), and geologic history and diagenesis in general (SIEGEL,1963). As some of these factors increase and others reduce the type and degree of luminescence, and because more than one factor can be influential at the same time or be effective in successive stages, it is not surprising that seemingly contradictory results have been obtained. Nevertheless limited success has been achieved: (I) in age determination (ZELLER,1954; ZELLER et al., 1955, 1957); (2) in correlating and zoning carbonate sediments (PARKS,1953; SAUNDERS, 1953; BERGSTROM, 1956, LEWIS,1956; PITRAT,1956; DANIELS, 1958); (3) for measuring calcite-dolomite contents (LEWIS,1956; PITRAT,1956); (4) in determining origin of dolomites (SIEGEL,1963); (5) in the study of biogenic calcium carbonate (JOHNSON, 1960);

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and (6) in the investigation of temperature and pressure histories (HANDINet al., 1957; ANGINO,1959). On the other hand, many similar studies have indicated that despite the occasional successful application of thermoluminescence, it is not a reliable tool as yet and more basic research is required as has been pointed out by most of the investigators. (See also Hsu, 1967.)

RADIOCARBON DATING OF CARBONATE SEDIMENTS

The dating of sediments by the 14C method has been described, for example, by LIBBY(1955), RANKAMA (1956), EMERYand BRAY(1962) and ~ S T L U N Det al. (1962). This is an invaluable tool for determining the approximate absolute age of recent carbonate deposits; it is particularly useful, therefore, in measuring the rates of sedimentation. A number of modifying influences exist, however, that cause either an increase or decrease of apparent ages because of dilution and alteration effects. Charcoal, well-preserved wood, and peat sometimes prove to be more reliable for 14C dating. In any case, there are cosmic controls that lead to variations in 14C productivity by as much as 2 %. TAFTand HARBAUGH (1964, p. 113) recently discussed the discrepancies between radiocarbon ages of different components in carbonate sediments. Both carbonate carbon and organic carbon were analyzed. “Of ten samples, six yielded greater ages for carbonate carbon in respect to organic carbon, three yielded smaller ages for carbonate carbon in respect to organic carbon, and one yielded the same age for carbonate carbon in respect to organic carbon.” The reasons for the differences in radiocarbon ages of carbonates and organic carbons are poorly understood, but they suggested four possible reasons (see also FAIRBRIDGE, 1961). (I) In analyzing carbonate sediments it is possible that the material consists of particles derived from different geographic sources and rocks that vary in age. TAFTand HARBAUGH (1964, p.113) gave an example of this. A similar case has been pointed out by EMERY and BRAY(1962), and WOLF(1965a,c). (2) Another possibility is that the organisms used carbon deficient in 14C in comparison to the proportion of 14C in the atmosphere. For example, “old” carbonate carbon may reach the environment in which the organisms live via rivers that drain land areas with ancient carbonate rocks. Thus, 14C deficiency causes the skeleton to appear older than it is in reality. (3) Burrowing organisms such as burrowing clams and worms may contribute younger organic material to buried sediments. (4) Many animals take in finely divided carbonate particles with their food, and if the organisms absorb some of the carbonate particles that may have “older” carbonate carbon (see I) and secrete skeletal carbonate, the 14Cdates of the latter may be anomalous. EMERY(1960) and EMERY and BRAY(1962) have dated different fractions

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of the samples collected, namely, Foraminifera, fine-grained carbonate, total carbonate, and extracted carbon. These two investigators concluded “. . . after considering the various pieces of evidence . that the total organic carbon is the most reliable dating medium for the basins off Southern California.” Other possible modifying factors that increase or decrease the apparent ages determined by 14C method are discussed by KEITHand ANDERSON (1963) and RUBINet al. (1963). The former concluded that the errors in determining radiocarbon dates of shell material may be as large as several thousand years. BERGER et al. (1964), however, indicated that conchiolin of shells, similar to collagen in bones, can be prepared for dating; this may give more reliable results than dating of the calcium-carbonate shell material, because secondary changes are less likely to occur in conchiolin than in the carbonate skeleton. The published results indicate that the interpretation of radiocarbon age dates, in particular in the case of the 14Cmethod, is still marked by many uncertainties. Aside from determining the precise half-life of 14C, which was assumed as being 5,568 f 30 years by LIBBY(1955), but now raised to 5,730 f 40’years (see GODWIN,1962), many primary and secondary factors that control the radiocarbon content are poorly understood. Continued emphasis on research concerning the basic problems, no doubt, will increase the reliability of 14C dating of carbonate sediments. It should also be mentioned that research is in progress on the use of traces of uranium, helium, protactinium, and thorium in carbonates for absolute age 1959; BROECKER, 1963; THURBER et al., determination (TATSUMOTO and GOLDBERG, 1963; FANALE and SCHAEFFER, 1964).

..

ISOTOPE INVESTIGATIONS OF CARBONATE SEDIMENTS

Isotope investigations are being made at an ever-increasing rate in solving problems in carbonate rock petrology. Most of the work has been conducted on the ratios of 1 8 0 / 1 6 0 and 13C/W, and in isolated cases on 24Mg/26Mg(and also 48Ca/Wa/ (total Ca) ratios). Some of the more recent papers that describe the theory of isotope fractionation and analytical procedures, and provide references to earlier publications, are those by MCCREA(1 950), CRAIG(1953), JEFFERY et al. (1959, RANKAMA (1956), CLAYTON and EPSTEIN(1958), and DAUGHTRY et al. ( 1962). Although considerable information is available on the elemental distribution of Sr (WOLFet al., 1967), only a few investigations appear to have been made on its isotopes. WICKMAN (1948), KULP(1950), and KULPet al. (1952) suggested a possible use of Sr isotopes for age determination. On the other hand, HERZOG et al. (1953) indicated that it would be difficult to use strontium for that purpose (see RANKAMA, 1956, p.337).

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Investigations of 13C/"T ratio have been used: (I) to distinguish between marine and fresh-water or terrestrial calcareous material (CRAIG,1953; CLAYTON and DEGENS, 1959; J. C. VOGEL,1959; LOWENSTAM, 1961; DEGENS and EPSTEIN, 1962b, 1964; KEITHand ANDERSON, 1962;LLOYD,1964; WEBER,1964; WEBER et al., 1964); (2) in studies of dolomite genesis and limestone petrology (DEGENS and EPSTEIN, 1962a, 1964; Ross and OANA,1961;WILLIAMS and BARGHOORN, 1963); (3) to study calcareous varves (WEBER,1964); and (4) in investigating diagenetically altered carbonates (WICKMAN and VONUBISCH,1951; JEFFERYet al., 1955; COMPSTON, 1960; Ross and OANA,1961; WEBER and ROCQIJE, 1963; DEGENS and EPSTEIN, 1964; GROSS, 1964; LLOYD,1964). A number of the isotope studies revealed phylogenetic differences of faunal and floral calcium carbonate (CRAIG, 1953, 1954; REVELLE and FAIRBRIDGE, 1957; LOWENSTAM, 1961; KEITHand ANDERSON, 1962; GROSS,1964; LLOYD,1964; TAFTand HARBAUGH, 1964). The isotope studies undertaken by LOWENSTAM and EPSTEIN(1957) suggested that many of the Recent aragonite needle deposits may have been formed,by the disintegration of calcareous Algae. Similar approaches may assist in discriminating for example between algal, bahamite, and faecal pellets. The ratio 1 8 0 / 1 6 0 has been utilized: (I) in establishing paleotemperatures (UREYet al., 1951; EPSTEIN et al., 1953; CLAYTON and EPSTEIN, 1958; FLUGEL and FLUGEL-KAHLER, 1963; EMILIANI, 1964; LLOYD,1964); (2) in distinguishing between syngenetic, diagenetic, hydrothermal and metamorphic carbonates (ENGELet al., 1958; DEGENS and EPSTEIN, 1964); (3) in ore investigations (ENGELet al., 1958); (4) in dolomite studies (DEGENS and EPSTEIN, 1962a, 1964); (5) in general petrogenesis and diagenesis of carbonate sediments (CLAYTON and EPSTEIN, 1958; DEGENS and EPSTEIN,1962a, 1964; FLUGELand FLUGEL-KAHLER, 1963; GROSS,1964; WEBER,1964); and (6) in the discrimination between marine and fresh-water sediments (DEGENS and EPSTEIN, 1962a, 1964). Differences in oxygen-isotope composition of some right- and left-coiled Foraminifera and their influence on the accuracy of isotope data are discussed by LONGINELLI and TONGIORGI (1964). DAUGHTRY et al. (1962) have shown that future work on magnesium isotopes may prove to be a valuable approach in solving genetic problems of dolomites and possibly other Mg-containing carbonates. Finally, 45Ca has been used in determining the mode, location, rate, and amount of calcium carbonate deposition by a number of shell-forming organisms (BEVELANDER, 1952; WILBURand JODREY, 1952; JODREY, 1953). More detailed information on isotope studies related to carbonate mineralogy and petrology is given by DEGENS (1967).

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REFERENCES

ALEXANDER, L. E. and KLUG,P. H., 1959. X-Ray Diffraction Procedures, 2 ed. Wiley, New York, N.Y., 716 pp. ANGINO, E. E., 1959. Pressure effects on thermoluminescence of limestone relative to geologic age. J. Geophys. Res., 64: 569-573. ANGINO, E. E. and SIEGEL,F. R., 1959. The effects of trace elements on natural thermoluminescence. Compass, 36: 296-303. G., KJELLBERG, G. and LIBBY,W. F., 1951. Age determination of Pacific chalk ooze ARRHENIUS, by radiocarbon and titanium content. Tellus, 3: 222-229. AZ~ROFF, L. V. and BUERGER, M. J., 1958. The Powder Method in X-Ray Crystallography. McGrawHill, New York, N.Y., 342 pp. BANKS,J. E., 1950. Particle-type well logging. Bull. Am. Assoc. Petrol. Geologists, 34: 1729-1736. BARLETT, H. H., 1951. Radiocarbon datability of peat, marl, caliche and archeological materials. Science, 114: 55. BARNES, V. E., 1959. Thermoluminescence of Pre-Simpson Paleozoic rocks. In: V. E. BARNES, P. E. CLOUD,L. P. DIXON JR., R. L. FOLK, E. C. JONAS,A. R. PALMER and E. J. TYNAN (Editors), Stratigraphy of the Pre-Simpson Paleozoic Subsurface Rocks of Texasand Southeast New Mexico-Wniv. Texas, Publ., 5924: 293 pp. G., CAILLBRE, S.,LAGRANGE, R. et POBEGUIN, TH.,1959. Etude du Mondmilch de la Grotte BARON, de la Clamouse et de quelques carbonates et hydrocarbonates Alcalino-Terreuk. Bull. Soc. Franc. Mindral. Crist., 82: 150-158.

BAYLISS, P., 1964. Effect of particle size on differential thermal analysis. Nature, 201: 1019. BAYLISS, P. and WARNE,S., 1962. The effects of controllable variables on differential thermal analysis. Am. Mineralogist, 47: 775-778. BEALES, F. W., 1960. Limestone peels. J. Alberta SOC.Petrol. Geologists, 8: 132-135. BECK,C. W., 1950. Differential thermal analysis curves of carbonate minerals. Am. Mineralogist, 35: 985-1013.

BERG,L. G., 1943. Influence of salt on the dissociation of dolomite. Dokl. Akad. Nauk S.S.S.R., 38: 24-27.

BERGER, R., HORNEY, A. G. and LIBBY,W. F., 1964. Radiocarbon dating of bone and shell from their organic components. Science, 144 (3621): 999-1001. BERGSTROM, R. E., 1956. Subsurface correlation of some Pennsylvanian limestones of the Midcontinent by thermoluminescence. Bull. Am. Assoc. Petrol. Geologists, 40: 918-942. BERRY,L. G. and MASON,B., 1959. Mineralogy, Descriptions, Determinations. Freeman, San Francisco, Calif., 630 pp. G., 1952. Calcification in molluscs. 111. Intake and deposition of 45Ca and 32P in BEVELANDER, relation to shell formation. Biol. Bull., 102: 9-15. BISQUE, R. E., 1961. Analysis of carbonate rocks for calcium, magnesium, iron, and aluminium with E.D.T.A. J. Sediment. Petrol., 31: 113-122. BISQUE,R. E. and LEMISH,J., 1958. Chemical characteristics of some carbonate aggregate as related to durability of concrete. Highway Res. Board, Bull., 196: 129-145. BISQUE,R. E. and LEMISH, J., 1959. Insoluble residue-magnesium content relationship of carbonate rocks from the Devonian Cedar Valley Formation. J. Sediment. Petrol., 29: 73-76. BISSELL, H. J., 1957. Combined preferential staining and cellulose peel technique. J. Sediment. Petrol,, 27: 417-420.

BLOSS,F. D., 1961. An Introduction to the Methods of Optical Crystallography. Holt, Rinehart and Winston, New York, N.Y., 294 pp. BOUMA,A. H., 1962. Sedimentology of some Flysch Deposits. A Graphic Approach to Facies Interpretation. Elsevier, Amsterdam, 168 pp. BRADLEY, D. E., 1954. Evaporated carbon films for use in electron microscopy. Brit. J. Appl. Phys., 5 : 65-66. BRADLEY, D. E., 1960. Replica techniques in applied electron microscopy. J. Roy. Microscop. SOC.,79: 101-118.

BRADLEY, W. F., BURST,J. F. and GRAF,D. L., 1953. Crystal chemistry and differential thermal effects of dolomite. Am. Mineralogist, 38: 207-218.

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BRILL,O., 1905. Ober die Dissoziation der Karbonate der Erdalkalien und des Magnesiankarbonates. Z. Anorg. Allgem. Chem., 45: 285. BRINDLEY, G. W., 1961. Experimental methods. In: G. BROWN(Editor), The Identification and Crystal Structures of Clay Minerals. Mineral. Soc.(Clay Mineral Group), London, pp. 1-50. BROECKER, W. S., 1963. A preliminary evaluation of uranium series inequilibrium as a tool for absolute age measurement on marine carbonates. J. Geophys. Res., 68: 2817-2834. BROECKER, W. S. and ORR,P. C., 1958. Radiocarbon chronology of Lake Lahontan and Lake Am., 69: 1009-1032. Bonneville. Bull. Geol. SOC. BROWN,G. (Editor), 1961. The X-ray Identification and Crystal Structures of Clay Minerals. Mineral. SOC.(Clay Mineral Group), London, 544 pp. BUEHLER, E. J., 1948. The use of peels in carbonate petrology. J. Sediment. Petrol., 18: 71-73. BURGER, D., 1963. Notes on some carbonate minerals in the iron ore deposits of the Iron Duke Area, South Middleback Range, South Australia. Australian lnst. Mining Met. Proc., 208: 55-80. CAILLZRE, S., 1962. Rappel de la signification des phknomtnes thermiques ii propos de I’ttude de la sidbose. Bull. Soc. Franc. Mineral. Crist., 85: 122-124. CAILL~RE, S. et POBEGUIN, TH., 1960. Contribution ii l’ktude des carbonates simples anhydres. Bull. Sor. Franc. Mineral. Crist., 83: 3641. CALVERT, S. E. and VEEVERS, J. J., 1962. Minor structures of unconsolidated marine sediments revealed by X-radiography. Sedimentology, 1 : 287-295. L. et PULOU,R., 1954. Nouveau dispositif d’analyse thermique difftrentielle. CAPDECOMME, Bull. Sor. Franc. Mineral. Crist., 17: 969-973. CAROZZI, A. V., 1950. Contribution A l’ktude des rythmes de sedimentation. Arch. Sci. (Geneve), 3: 1740,95-146. CAROZZI,A. V., 1958. Micromechanisms of sedimentation in the epicontinental environment. J. Sediment. Petrol., 28: 133-150. CHAVE, K. E., 1954. Aspects of the biochemistry of magnesium. 2. Calcareous sediments and rocks. J. Geol., 62: 587-599. CHENG,K. L., KURTZ,T. and BRAY,R. H., 1952. Determination of calcium, magnesium and iron in limestones. Anal. Chem., 24: 1640-1644. CHILINGAR, G. V. and TERRY,R. D., 1954. Simplified technique of determining calcium and magnesium content of carbonate rocks. Petrol. Engr., 26 (12): 368-370. CHILINGAR, G. V., BISSELL, H. J. and WOLF,K. H., 1967. Diagenesis of carbonate rocks. In: G. LARSEN and G. V. CHILINGAR (Editors), Diagenesis in Sediments. Elsevier, Amsterdam, in press. CLAYTON, R. N., 1959. Oxygen-isotope fractionation in the system carbonate-water. J. Chem. Phys., 30: 1246-1250. CLAYTON, R. N. and DEGENS, E. T., 1959. Use of carbon-isotope analyses for differentiating freshwater and marine sediments. Bull. Am. Assoc. Petrol, Geologists, 43: 89G897. CLAYTON, R. N. and EPSTEIN,S., 1958. The relationship between 1sO/160ratios in coexisting quartz, carbonate and iron oxides from various geological deposits. J. Geol., 66: 352-373. CLOWES, F. and COLEMAN, J. B., 1944. Quantitative Chemical Analysis, 15 ed. Churchill, London, 90 PP. COMPSTON, W., 1960. The carbon isotopic compositions of certain marine invertebrates and coals from the Australian Permian. Geochim. Cosmochim. Arta, 18: 1-22. CRAIG,H., 1953. The geochemistry of the stable carbon isotopes. Geochim. Cosmochim. Acta, 3: 53-92. CRAIG,H., 1954. Carbon-13 in plants and the relation between carbon-13 and carbon-I4 variations in nature. J. Geol., 62: 115-149. CUVILLIER, J., 1951a. Correlations Stratigraphiques par Microfacies en Aquitaine Occidentale. Brill, Leiden, 34 pp. J., 1951b. Abstract of Cuvillier (1951a), and discussion by Henson, Thomas, and CUVILLIER, Reichel. World Petrol. Congr., Proc., 3rd, The Hague, 1951, Sect. I , Geol. Geophys., pp.44W8. F. L. and ROWLAND, R. A., 1947. Differential thermal analysis of some carbonate CUTHBERT, minerals. Am. Mineralogist, 32: 1 1 1-1 16.

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EXAMINATION A N D ANALYSIS OF SEDIMENTARY CARBONATES

34 1

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Chapter 9

PROPERTIES AND USES OF THE CARBONATES FREDERIC R. SIEGEL

Department of Geology, The George Washington University, Washington, D.C. (U.S.A.)

SUMMARY

Carbonate rocks are raw materials indispensable to industrial development. In recent years, limestone, dolomite, and marble constituted more than 70% of all rocks quarried in the United States. Statistics on production and dollar value for 1961, 1962, and 1963 are presented, by uses. The uses to which carbonate rocks and minerals can be put is a function of their physical and/or chemical properties. This chapter contains listings of selected chemical analyses and important physical properties of carbonate rocks. More than one hundred uses for carbonate rocks and minerals are given together with the users’ general chemical and physical requirements. Because of space limitations, only three of the many areas of active research on carbonate properties are discussed: solid solution and subsolidus relations, thermoluminescence, and infrared absorption.

SOME ASPECTS AND STATISTICS OF CARBONATE ECONOMICS

A myriad of uses exist for carbonate minerals and rocks or products derived from them. Indeed, industrial development in the United States and other areas of the world is often reflected in the number of tons of carbonate raw material produced and sold each year. If, for example, there were a cut-back in steel production or a lag in building construction, there would generally be a concomitant drop-off in the quarrying of carbonate rock. Similarly, a reduction in funds for state and federal highway development programs would cause a great drop in carbonate quarrying. During 1962, more than 70% of all rock quarried in the United States was limestone, dolomite, and marble. Crushed and broken stone comprised a major part of the carbonate rock production, and 93 % of almost 500 million short tons (representing about U.S.$ 600 million) was used for concrete and road stone, cement (Portland and natural), flux, agriculture, and lime and dead-burned dolomite. In Table I there is a categorization of statistics on production and dollar value ~-

l

Former address: The University of Kansas, State Geological Survey, Lawrence, Kans. (U.S.A.).

TABLE I CARBONATE ROCKS SOLD OR USED BY PRODUCERS IN THE UNITED STATES, BY USES] ~

1961 Quantity (x 1,000 short tons)

-

Value (x US.$ 1,000)

1962

Quantity ( x 1,ooo short tons)

1963

Value (x US.$ 1,m)

-

Quantity ( x 1,m short tons)

Value (x

US.$

1,000) ~~

Limestone and dolomite (crushed and broken stone) concrete and roadstone 258,997 flu 27,198 agriculture 22,196 railroad ballast 4,260 riprap 9,138 alkali manufacture 2,560 calcium-carbide manufacture 764 cement (Portland and natural) 79,779 coal-mine dusting 372 fill material 266 filler (not whiting substitute): asphalt 2,130 fertilizer 438 other 219 filtration 148 glass manufacture 1,211 lime and dead-burned dolomite 18,124 limestone sand 1,693 limestone whiting3 802 mineral food 695 paper manufacture 400 poultry grit I53

338,798 39,725 38,478 5,376 10,440 2,878 785 85,883 1,527 277

276,878 26,081 23,029 5,065 10,016 2,840

365,098 36,821 39,348 6,578 12,253 3,188

292,976 27,185 25,956 4,923 10,690 2,955

380,893 39,322 44,195 6,4 10 13,229 3,282

83,318 400 440

92,886 1,667 330

86,842 539 383

92,646 2,268 296

5,408 1,080 873 22 1 3,736 28,283 2,596 9,242 3,723 1,129 1,185

3.208 448 35 1 79 1,337 19,356 1,706 838 692 27 1 161

6,955 1,132 1,567 141 4,294 32,959 3,103 9,639 3,847 82I 1,333

1,994 457 419 62 1,492 21,450 1,759 785 618 358 160

5,012 1,133 1,921 117 4,781 36,024 3,234 9,298 3,793 1,099 1,342

*2

*2

*2

*2

w

refractory (dolomite) suger refining other uses4 uses unspecified subtotal

235 882 2,838 1,900

465 2,215 4,603 2,475

322 623 1,741 1,753

563 1,506 4,253 2,518

769 646 2,125 2,805

1,297 1,580 5,472 3,282

437,398

591,401

460,953

632,800

488,348

661,926

Marble (crushed and broken stone) terazzo other uses5

397 1,038

4,535 7,859

3 80 1,243

4,866 9,512

367 1,385

4,768 8,797

subtotal

1,435

12,394

1,673

14,378

1,752

13,565

ga 0

8w

-

i* 2: U

8 e i2

* c1

0

2

Limestone (dimension stone) building rough: construction architectural dressed: sawed and cut rubble curbing and flagging

61 223 330 219 22

323 3,455 12,066 725 169

82 197 318 284 15

326 3,000 12,476 928 117

52 196 347 282 18

subtotal

855

16,738

896

16,847

895

18,134

Marble (dimension stone) buildings rough; architectural dressed: sawed and cut monumental: rough and finished

37 106 14

1,168 14,670 2,728

34 95 17

1,330 14,269 3,140

28 80 42

1,334 12,574 7,294

subtotal

157

18,566

146

18,739

150

2 1,002

4

v1

289 3,091 13,498 1,104 152 ~

.~

w

R

TABLE I (continued) 1961 Quantity ( x 1,000 short tons)

1963

1962 Value ( x U.S.$ 1,000)

Quantity

short tons)

1,000)

.rhort tons)

Value ( x U.S.b 1,000)

(x

1,OOo

Value ( x U.S.%

Quantity ( x 1,000

~

Shell concrete and road material cement lime poultry grit mineral food other uses7

subtotal Calcareous marl agriculture cement

subtotal grand total

4,406 1,420 598 3 78

18,256 4,881 1,782 5,004 14 438

12,792 5,117 1,441 581 4 113

18,611 5,531 1,876 4,635 22 566

11,821 5,278 1,169 552

17,277 5,847 1,663 3,874

I99

759

18,004

30,375

20,054

31,241

19,019

29,420

223 876

168 819

226 956

156 855

260 904

178 811

1,099

987

1,182

1,Ol I

1,164

989

458,948

670,461

485,042

715,016

511,328

745,036

1 1,499

*2

*2

Data for 1961 and 1962were given by ANONYMOUS (1963), those for 1963by ANONYMOUS (1964a). Included with “other uses”. 3 Includes stone for filler, abrasives, calcimine, calking compounds, ceramics, chewing gum, fabrics, floor coverings, insecticides, leather good, paint, paper, phonographic records, plastics, pottery, putty, roofing, rubber, Wire coating, and unspecified uses. Excludes limestone whiting made by companies from purchased stone. 4 Includes stone for acid neutralization, calcium carbide (1962), cast stone, chemicals (unspecified), concrete products, disinfectant and animal sanitation, electrical products, magnesia, magnesite, magnesium, mineral wool, oil-well drilling, patching plaster, rice milling, road base, roofing granules, stucco, terrazo, and water treatment. Stone for agriculture, asphalt filler, flux, poultry grit, roofing, stone sand, stucco, whiting and unspecified uses. 1961: US.$ 8,934,000 for exterior use, U.S.$ 6,904,000 for interior use; 1962: US.$ 9,575,000 for exterior use; U.S.$ 6,024,000 for interior use; 1963: US.$ 7,351,000 for exterior use; U.S. $ 6,357,000 for interior use.

’Agriculture, asphalt filler to whiting.

347

PROPERTIES A N D USES OF THE CARBONATES

TABLE I1 CEMENT PRODUCTION OF SELECTED COUNTRIES WHICH ACCOUNT FOR ABOUT WORLD PUODUCTlON

90%

OF THE TOTAL

(After ANONYMOUS, 1964c) 1961

Country

Argentina Austria Australia Brazil Belgium Canada China Czechoslovakia Denmark Egypt France Germany (eastern) Germany (western) India Italy Japan Korea (North) Mexico Pakistan Poland Roumania South Africa Spain Sweden Switzerland Turkey U.S.S.R. United Kingdom United States Yugoslavia World total

* Estimate made by the U.S.

I962

(long tons)

(long tons)

2,856,900 3,035,450 2,813,000 4,636,341 4,678,792 5,541,025 9,800,000* 5,259,000 2,879,140 2,107,000 15,138,469 5,192,000 26,714,000 8,114,000 17,698,986 24,243,000 2,226,000 2,987,149 1,223,000 7,248,000 3,255,538 2,557,420 6,408,005 2,964,000 3,544,292 1,995,971 50,194,000 14,149,000 56,841,100 2,299,000 33I ,000,000

2,857,000 3,008,830 2,887,000 4,992,000 4,817,296 6,059,133 8,900,000* 5,620,000 2,937,900 2,260,000 16,433,000 5,346,000 28,141,000 8,450,000 19,838,415 28,33 1,000 2,338,000 3,299,000 1,373,000 7,422,000 3,434,129 2,616,870 6,342,000 3,006,000 3,667,018 2,279,961 56,394,000 14,030,000 59,074,300 2,478,000 353,000,000

Bureau of Mines.

for most of the carbonate rock sold or used by producers in the United States in 1961, 1962, and 1963, by uses. No such detailed data are available on a worldwide basis. Cement production figures, however, have been published and are presented in Table 11. They show that in 1962, 30 countries accounted for about 90% of the world production of 353 million long tons of cement. During 1962, seven countries (China, France, Germany, Japan, the United Kingdom, the U.S.S.R., and the United States) produced over 75 % of the world total of 618 mil-

348

F. R. SIEGEL

lion long tons of steel ingots and castings, pig iron, and ferro-alloys. Ifone can extrapolate from this to the amount of carbonate rocks (or derivatives) used in the siderurgical industry, an extremely conservative estimate would be well over 1,000 million long tons. In addition to their direct and indirect applications in many industrial processes, limestones and dolomites are reservoir rocks for more than one-half of the known petroleum reserves of the world (IMBT, 1950), and act as host rock for numerous important metalliferous ore deposits. Equally impressive is the fact that in many areas, the major source of water is from limestone aquifers. Although the practical (economic) value of the carbonates is emphasized in the later paragraphs of this chapter, one must not forget their meaning to the academician. In his study of fossils and other features commonly associated with the carbonate rocks, the geoscientist can often find clues for solving economic problems by delving into the geologic past, reconstructing environments that existed at the time of their formation, developing fundamental concepts, and establishing parameters which could show trends important to successful exploitation.

PROPERTIES

Introduction

The physical, chemical, optical, and other properties of carbonate rocks influence (within certain limits) their economic potential, that is, the maximum number of uses they might serve. Because these properties are in great part determined by those of the carbonate mineral(s) in the rock and because the carbonate minerals themselves can be very valuable, selected physical, optical, and crystallographic properties of the economically important carbonate minerals are presented here (Tables 111-V). These properties can be significantly altered by cationic substitution, especially in calcite and dolomite. In fact, much recent research has been devoted to the solid solution and subsolidus relations within the calcite group minerals. This aspect is discussed in another part of the chapter. Physical proper ties

Factors which most affect carbonate economics are the physical properties of the quarried material. For example, to be suitable for building stone, limestone, dolomite, or marble must be strong, durable, and reasonably workable; in addition, stone which has these qualities and is aesthetically pleasant to view, will have greater dollar value. Basic properties are given in Table VI. These are generally sufficient for the builders’ (architectural and engineering) needs, but there are many other physical

w

TABLE 111

E

PHYSICAL PROPERTIES OF SOME ECONOMICALLY IMPORTANT CARBONATE MINERALS

i+?i

(After LANGE,1956;DANA, 1959;KRAUSet al., 1959;and DEER et al., 1962) Mineral

Chemical formula Hardness (pure)

Specific gravity

Colour

Common impurities

Cleavage

colourless or white

Mn, Fe, Mg for Ca

(1011)perfect

pink, white, or colourless

Fe, Mn, Co, Zn for Mg, Pb for Ca Fe, Ca, Mn for Mg Fe, Ca, Mg, Zn for Mn Mn, Mg, Ca for Fe Fe, Mn, Ca, Mg, Cd, Cu, Co, Pb for Zn Sr, Pb,Zn for Ca

(1011)perfect

Sr, Ca for Ba

(010)and (110)

Ca for Sr

(1 10) good (1 10) good and

calcite

caco3

dolomite

CaMg(CO3)n

3 on (1011) 2.72 2.5 on base 2.85 3.54

magnesite rhodochrosite siderite smithsonite

MgC03 MnCOs FeCO3 ZnCOa

3.5-5 3.54 3.54 4-4.5

3.0-3.2 3.5-3.7 3.96 4.3M.45

white, gray, yellow, or brown rose-red or light pink brown brown or green

aragonite

CaC03

3.54

2.95

witherite

BaC03

3.5

4.3

colourless, white, or pale yellow colourless, white, or gray

strontianite cerussite

SrC03 PbC03

3.54 3-3.5

3.7 6.55

white, gray, yellow, or green colourless, white, or gray

malachite azurite

CuzCOa(0H)z 3.54 Cu3(OH)z(C03)2 3.54

3.9403 3.77

bright green intense azure blue

(1011)perfect (1011) perfect

(lOT1) perfect (1011)perfect (010) and (110)

imperfect

poor

(021)fair

(001) perfect

(021)imperfect

TABLE I V w

OPTICAL DATA ON THE ECONOMICALLY IMPORTANT CARBONATE MINERALS

VI

0

(After LARSENand BERMAN, 1934; WINCHELL and WINCHELL, 1951; MOOREHOUSE, 1959; and DEER et al., 1962) 2V

Dispersion

Colour in section

0.172-0.190

-

very high

co1our1ess

0.181-0.196

-

high

colourless

0.191-0.219

-

very high

colourless

0.220-0.221

-

high

0.207-0.242

-

high

0.228-0.225

-

high

co1our1ess to pink colourless to brown colourless

0.155

18-18.5'

low

colourless

0.148

16"

very low

colourless

0.1 50-0.149

7-10"

low

colourless

0.273-0.214

8-8.5"

high

colourless

0.254

43

high

green

0.108

68

low

blue

Mineral

System

Optic sign

Indices of refraction

Birefringence

calcite

hexagonal

uniaxial

dolomite

hexagonal

uniaxial

magnesite

hexagonal

uniaxial

rhodochrosite

hexagonal

uniaxial

siderite

hexagonal

uniaxial

smithsonite

hexagonal

uniaxial

ne=1.486-1.550 no=1.658-1.740 ne= 1.5W1.520 no = 1.681-1.716 ne=1.509-1.563 no=1.700-1.782 ne=1.597-1.605 no= 1.817-1.826 ne=1.575-1.633 no=1.782-1.875 ne= 1.621-1.625 no= 1.849-1.850 nz= 1.53G1.531 nu=1.680-1.682 nz= 1.685-1.686 nz =1.529 nu=1.676 nz=1.677 nz =1.516-1 520 nv= 1.664-1.667 nc= 1.666-1.669 nz=1.803-1.804 nu=2.0742.076 nz =2.076-2.078 nz =1.655 nu=1.875 n2=1.909 nz= 1.730 nu= 1.758 n2=1.838

(-1

(-1

(3

(-1

(-1

(-)

aragonite

orthorhombic

biaxial

witherite

orthorhombic

biaxial

orthorhombic

biaxial

strontianite

(-1

(-1

(-)

4

cerussite

orthorhombic

biaxial

malachite

monoclinic

biaxial

azurite

monoclinic

biaxial

(-1

(4

(+I

Optic axial plane

O

PROPERTIES AND USES OF THE CARBONATES

35 1

properties which have been measured and reported, and which must be known before a carbonate rock may be considered for a specializeduse. A classic compilation of quantities important for the physics and physical chemistry of geological materials was published by BIRCHet al. (1942) in the Handbook of Physical Constants. Selected data from this publication are presented in Tables VII-XIX. Methods of testing rock materials for several of their physical properties have been fairly well standardized by the American Society for Testing and Materials (A.S.T.M.). Many of these tests, however, were not directly applicable to samples obtained, for example, by diamond drilling techniques. Therefore, in a program designed to determine the petrographic and physical properties of mine rock and establish correlations between these properties and the costs of various mining operations, U.S. Bureau of Mines scientists began by developing or adapting methods for measuring the physical properties of rock from core specimens obtained by diamond drilling (OBERTet al., 1946). The standardization of testing methods was necessary first to demonstrate that the size of the sample or the testing conditions did not affect the results; second, to establish a correlation factor so that values obtained, which were influenced by size or testing methods, could be made to correspond to values obtained by a recognized standard technique. The physical properties treated were the following: apparent specific gravity, apparent porosity, compressive strength, tensile strength, modulus of rupture (flexural strength), impact toughness, abrasive hardness, scleroscope hardness, Young’s modulus (modulus of elasticity), modulus of rigidity, specific damping capacity, longitudinal bar velocity, apparent Poisson’s ratio, and grindability. This initial phase of the U.S. Bureau of Mines program was followed by a systematic investigation of the physical properties of mine rock from all parts of the United States. Results were published in a series of four papers (WINDES, 1949, 1950; BLAIR,1955, 1956), the last of which contains a complete index of all the rocks examined. These papers, titled: “Physical properties of mine rock, parts I, 11,111, and IV”, probably present the most complete data on the important physical properties of the carbonate (and other) rocks. Selected information from these papers are shown in Table XX where they can be compared with values given by other authors. (1 960a,b) briefly reviewed testing methods and physical properties GILLISON given by KESSLER and SLIGH(1927) and WOOLF(1953). Woolf‘s paper is especially interesting because in it are described physical tests crushed stone must undergo before it can be evaluated for use as road building aggregate for state and federai highway development programs. A test treated by Woolf but often omitted by other authors is that of soundness, that is, response of the rock to alternate freezing and thawing. One manne: of determining whether material is “sound”, “questionable”, or “unsound” is by immersing several fragments or blocks of the material in a saturated solution of Na2S04 for 16-18 h, drying them in an oven, repeating the test five times, and noting the damage to the fragments or blocks.

TABLE V CRYSTALLOGRAPHIC DATA ON SOME ECONOMICALLY IMPORTANT CARBONATE MINERALS

(After GRAF,1961; DEER et al., 1962; and A.S.T.M., 1963a) Rhombohedra1 Z # of forCleavage cell edge ( A ) mula unitslunit cell

Twinning

a =b =4.990 c =17.061

6.31

2

(lOT1) perfect

R5

a=b=4.807 c=16.01

6.01 5

2

(1OTl) perfect

magnesite

R3c

5.615

2

(loT1) perfect

rhodochrosite

R3c

5.91

2

(loT1) perfect

(01T2) rare (lamellar twins)

siderite

R3c

5.77

2

(10T1) perfect

smithsonite

RJc

4.432

2

(loll) perfect

(01T2) rare (lamellar twins) (OOO1) rare

aragonite

Pmcn

-

4

(010) imperfect (1 10) poor

(110) common (lamellar and repeated)

wi therite

Pmcn

-

4

Pmcn

-

4

(010) good (1 10) poor (012) poor (1 10) good (021) poor (010) poor (1 10) good (021) fair

(1 10) always present, repeated

strontianite

a=b=4.633 C = 15.016 a = b =4.111 ~=15.66 a=b=4.69 c=15.30 a= b =4.653 c=15.028 a = 4.95 b= 1.95 C = 5.13 a = 5.26 b= 8.84 C = 6.56 a = 5.13 b= 8.42 C = 6.09 a = 5.195 b= 8.436 C = 6.152

(01T2) very common (OOO1) common (loil) not common (OOO1) common (10T1) common (1120) common (loT1) rare (0221) glide twinning (OOO1) translation gliding to [loll]

Mineral

Space group Unit cell (A)

calcite

R3c

dolomite

cerussite

Pmcn

-

4

(110) common (single, repeated, and lamellar)

.a v1

(1 10) common (repeated)

B P

malachite

P21/A

azurite

P21IC

a = 9.502 b= 11.974 c= 3.240 a = 5.008 b= 5.884 c=10.336

-

4

(001) perfect

-

2

(021) imperfect

(100) common

TABLE VI SOME PROPERTIES OF LIMESTONE USED IN KANSAS AS BUILDING

STONE^

(After KANSSSBUILDING STONE ASSOCIATION, 1964) Name

Texture

Colour

Absorption ( %)

Specific gravity

Weight Compressive strength Temperature(Wcubicft.) normal parallel Weak salt to bed to bed efect (IbJsq. inch) (Ib./sq. inch)

Onaga Chestnut Shell Neva Cottonwood Silverdale Benton Kansas Cream

fine grain coquinoid dense, fine grain medium to fine grain medium to fine grain fine grain fine grain

light buff chestnut white gray light buff buff creamy

7.6 5.4 3.1 6.2 9.4 4.9 9.0

1.956 2.118 2.440 2.21 8 2.109 2.259 1.674

122 132 I52 139 137 141 I05

9,629 4,806 22,600 11,292 6,189 11,589 4,520

9,775 5,625 18,800 11,525 8,505 10,650 4,710

none none no data none none none none

The Kansas Building Stone Association prepared a pamphlet which serves as a guide for architects and engineers who need a rapid reference to the most important properties of Kansas building stone. Compression test (A.S.T.M. C170-50) determined by C. Crosier of Kansas University Civil Engineering Department. Absorption and specific gravity (A.S.T.M. C97-47) and temperature-weak salt (A.S.T.M. C218-48T) tests were made by the State Geological Survey of Kansas.

1

w

VI

w

354

F. R. SIEGEL

TABLE VII SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. POROSITY AND BULK DENSITY (DRY AND SATURATED)

(After BIRCHet al., 1942, table 2-6) Lithology and age

Location

limestone limestone, Carboniferous limestone, Silurian limestone. Caddo Lime, Pennsylvanian Greenhorn Limestone, Upper Cretaceous limestone, sugary, quartz-free oolitic limestone chalk dolomite marble marble, 34 samples

Porosity ( %)

Buxton'

14.1 2.2-9.4 -1 1.4-6.3 Dundee, Mich. 0.9 Ranger, Texas 4.4 Crook Co., Wyo. 37.6

Monk's Park'

-1

Mitcheldeanl

-1

from 12 states in U.S.A.

25.6 20.3 17.642.8 8.6 1.1 0.4-2.1

Bulk density dry

saturated

2.31 2.342.59 2.53-2.64 2.63 2.57 1.74

2.45 2.43-2.61 2.59-2.65 2.64 2.61 2.12

2.14 2.16 1.53-2.22 2.54 2.65 2.66-2.86

2.40 2.36 1.962.40 2.63 2.66 2.68-2.86

w1hz0

Known or unknown location in Great Britain.

TABLE VIII SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. THERMAL EXPANSION OF ROCKS, TEMPERATURE INTERVAL OF 20-100"c

(After BIRCHet al., 1942, table 3-4) Lithology

Number of determinations

Average linear expansion coefficient

* limestones marbles

20 9

355

PROPERTIES A N D USES OF THE CARBONATES

TABLE IX SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. COMPRESSIBILITY OF ROCKS AT LOW PRESSURES

(After BIRCHet al., 1942, table 4-13) Pressure (kglcm2)

Lithology

dolomite

107p

enclosed

0 120 600 0 120 600 0 120 600

marble (Vermont) limestone, Pennsylvanian (carbonaceous)

37.1 25.4 14.8 180.0 33.1 15.0 29.2 27.5 23.5

unenclosed 11.9 11.9 11.9 13.9 13.8 12.6 24.7 24.5 24.1

' p = compressibility, in reciprocal bars, at the pressures given.

TABLE X SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. COMPRESSIBILITY OF ROCKS AT HIGH PRESSURES

(After BIRCHet al., 1942, table 4-14) Lithology

Location

Pressure (bars)

lO7/?1

marble (enclosed)

Colorado

7,000

13.8 (18°C)

Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria Solnhpfen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria

6,000 6,000 5,000

13.6 (30°C) 14.2 (75 "C) 12.9 (6°C) 14.2 (100°C) 16.3 (270°C) 17.1 (476°C)

limestone (unenclosed, linear method)

lp=

5,000

5.000 5,000

compressibility, in reciprocal bars, at the pressures given.

F. R. SIEGEL

TABLE XI SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. ELASTIC CONSTANTS OF ROCKS AT ORDINARY PRESSURE AND TEMPERATURE^

(After BIRCHet al., 1942, table 5-4) G3 (dynes/cm2) (dyneslcm2)

Lithology

Location

E2

limestone

Knoxville, Tenn. Montreal, Que. Solnhofen, Bavaria

6.2 I 6.35 5.77

(2.48) (2.50) 2.31

dolomite

Pennsylvania-I Pennsylvania-2

7.10 9.30

3.23 3.62

marble

Dinant, Belgium Rutland, Vt.

7.24 5.24

(2.98) (2.07)

a4

Stress (kglcm2)

0.25 1 0.252 (0.25)

70-600 70-600

0.278 0.263

70-600 70400

Values of G or u in parentheses have been derived from the measurements by the use of the connecting equations for isotropic materials.. ?E= Young's modulus. 3G= modulus of rigidity. 4u= Poisson's ratio (dimensionless).

1

TABLE XI1 SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. EFFECT OF STRESS ON YOUNG'S MODULUS OF ROCKS, BY THE METHOD OF FLEXURAL VIBRATIONS OF LOADED BARS

(After BIRCHet al., 1942, table 5-5) Lithology _

_

Location _

~

limestone

Bedford, Ind. Bedford, Ind.

marble

Danby, Vt. Danby, Vt. Danby, Vt. Danby, Vt.

marble

Cockeysville, Md.

Orientation of axis'

Density (glcm3)

I

/I lI

/I

I I

EO2

Ea3

(dynes/cm2)

(dyneslcm2)

2.23 2.35

2.86 * 10" 3.48 * lo1'

2.97 * 10" 4.07. 10"

2.70 2.70 2.70 2.70

6.01 . 10" 6.48 . 10" 4.36. 10" 3.66. 1011

6.99 . 10" 7.24 . loll 6.94. 10" 5.81 . 10"

2.86

7.10 * 10"

8.84 * lo1'

1 Orientation of the axis of the bar with respect to the bedding plane. 2Eo= Young's modulus at zero stress. 3Ea= Young's modulus at a strsss not quite great enough to cause failure (500-1,OOO kglcm2).

351

PROPERTIES AND USES OF THE CARBONATES

TABLE XI11 SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. ELASTIC PARAMETERS OF CERTAIN ROCKS AT

4,000 kg/cm2 AND 30°C'

(After BIRCHet al., 1942, table 5-8) Lithology

Locat ion

E2 (dynes/ cm2)

G3 (dynes/ cm2)

P4

u5

(cmz/ dyne)

VP6

V87

(kmlsec)

(kmlsec)

limestone

Solnhofen, Bavaria

6.3

2.47

21.4

0.276

5.54

3.08

marble

Vermont

8.7

3.33

13.9

0.299

6.51

3.49

1 Values computed for the measured G and u by the use of equations for isotropic materials. The rocks were enclosed. 2E= Young's modulus. 3G= modulus of rigidity. 4 8 = volume compressibility 5u= Poisson's ratio (dimensionless). 6Vp= velocity of propagation of compressional waves in an infinite medium. 7 V8= velocity of propagation of distortional waves in an infinite medium.

TABLE XIV SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. RIGIDITY AND VELOCITY OF SHEAR WAVES AS A FUNCTION OF

PRESSURE^

(After BIRCHet al., 1942, table 5-9) Lithology Location

G2

P=I

vs3

P=500

P=4,000 P = l

P=500

P=4,000

limestone Solnhofen, Bavaria 1.96 Pennsylvania 2.67

2.20 2.88

2.47 3.00

2.75 3.15

2.91 3.27

2.47 3.34

dolomite Pennsylvania

3.49

4.20

-

3.5

3.87

-

marble

1.57

3.18

3.33

2.4

3.42

3.49

Proctor, Vt.

30°C. These results were obtained by a dynamical method, with All measurements made enclosed specimens. 2G= modulus of rigidity, in units of 10" dynes/cm2. 3Vs= velocity of shear or distortional waves, in km/sec. 4P= hydrostatic pressure, in kg/cm2. 1

358

F. R. SIEGEL

TABLE XV SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. STANDARD CRUSHING STRENGTHS OF ROCKS

(After BIRCHet al., 1942, table 9-1) Lithology

Number of localities

Average strength (kglcm2)

Range (kg/cm2)

limestone marble

216 76

960 1,020

60-3,600 3 1 O-2,620

TABLE XVI SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. SHORT TIME COMPRESSIVE STRENGTH OF UNJACKETED MATERIALS WITH CONFINING PRESSURE OF KEROSENE~

(After BIRCHet al., 1942, table 9-6) Lithology

Location

limestone

Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria

2,560 2,600 3,260 4,000 5,970 > 13,000

marble

location location location location location

810 860 1,650 > 5J00 > 11,400

Strength pressure.

= p1-p2

Confining pressure (kglcm2)

not given not given not given not given not given

at failure, where pi = axial compressive strength and p2

Strength (kglcm2)

= lateral confining

359

PROPERTIES AND USES OF THE CARBONATES

TABLE XVII SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. THERMAL CONDUCTTVITY (AT1 atm PRESSURE)

(After BIRCHet al., 1942, table 17-4) Lithology

Temperature Conductivity K cal.lsec cm degree Wlcm degree

Location

( "C)

limestone

Solnhofen, Bavaria Solnhofen, Bavaria Solnhofen, Bavaria

limestone, (carbona- Pennsylvania ceous), parallel to Pennsylvania bed Pennsylvania

0 100 200

7.2 . 10-3 5.5.10-3 4.8.10-3

30.1 .lo-3 23.1 . 20 10-3

0 100 200

8.2 . 10-3 7.0.10-3 6.5 10-3

.

34.5.10-3 29.5.10-3 27.4 10-3

-

ceous), perpendicular Pennsylvania

100

0

6.1 . 10-3 5.4 . 10-3

25.5 .10-3 22.6.10-3

limestone, dolomitic Longford Mills, Ont. Longford Mills, Ont. Longford Mills, Ont. Longford Mills, Ont. Queenston, Ont. Queenston, Ont. Queenston, Ont. Queenston, Ont.

130 181 268 377 123 177 254 332

3.9. 10-3 3.8.10-3 3.7.10-3 3.2.10-3 3.4 10-3 3.4.10-3 3.3 10-3 3.2. 10-3

16 10-3 16 10-3 15 .10-3 13 . 10-3 14 .10-3 14 .10-3 14 .10-3 13 10-3

0

2.2.10-3 11.9 10-3

-

9.2.10-3 49.8 .10-3

100 200

9.3 10-3 8.0 . 10-3

38.9.10-3 33.3 10-3

30

5.~7.7.10-3

124 210 334

3.7 10-3 3.6. 10-3 3.3 10-3

limestone, (carbona- Pennsylvania to bed

chalk dolomite marble (17 varieties) marble (black)

St. Albert, Ont. St. Albert, Ont. St. Albert, Ont.

-

-

-

-

-

21-32

TABLE XVIII SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. ELECTRICAL RESISTIVITY

(After BIRCHet al., 1942, table 21-1) Lithology

limestone

marble

Location

Spain Missouri Kentucky France France France

Resistivity (Q em) 3.105 104 104-105 105 10'0

4 * 108

109 10'0

.10-3

-

16 10-3 15 10-3 14 .10-3

360

F. R. SIEGEL

TABLE XIX SELECTED PHYSICAL CONSTANTS OF CARBONATE ROCKS. DIELECTRIC CONSTANT

(After BIRCHet al., 1942, table 21-7) Lithology

chalk coral dolomite dolomite limestone marble marmorized limestone

Dielectric constant (range)

8.0-9.0 8.0-9.0 7.3 8.0-12.0 8.3 15.2

Research on newer testing methods is continuously in progiess. CROW(1963) presented an easy and precise optical method for determining Poisson’s ratio. DURELLI and FERRER (1963) have developed a simple and somewhat novel way of determining Young’s modulus and Poisson’s ratio, which could be practical when speed is required or when measurements have to be made inside furnaces. These authors expect the method to be especially useful for materials used in three dimensional photoelastic studies. Chemical composition The chemical property of the carbonates which most influences their potential usefulness is the chemical composition. Iron content, for example, is undesirable in limestones to be used as dimension stone, because with weathering, the iron will alter to the oxide, and stain the stone surface a reddish or brownish color. The American Society for Testing and Materials, the U.S. Bureau of Standards, the British Standards Institution, and similar organizations publish results of the investigations and give recommendations as to the limits of impurities that can be tolerated in carbonates for industrial use. Stringent control must be maintained on the chemical composition of the limestone used in the manufacture of many economically important products. Thus, for the production of the better grades of glass, a maximum of only 0.2 % iron oxide is allowable in the limestone used in the manufacturing process, and for flint glass this impurity must not exceed 0.03 % (JOHNSTONEand JOHNSTONE, 1961). It must be remembered, however, that the economics of industrial operations often dictates that a raw material, less pure than that recommended, be used so that the end product is obtained at a maximum profit. This is true in the metallurgical industry in which both the economics and the processes affect the acceptibility of a carbonate rock considered as a fluxing agent for the removal of silica, alumina,

PROPERTIES A N D USES OF THE CARBONATES

361

and other undesirable impurities from the ore rock. For the production of pig iron from iron ore in the blast furnace process, the limestone flux should contain less than 1.5% silica, and less than 0.1 % each of sulphur and phosphorus; but because of the logistics of individual operations, more silica and up to 0.5 %percent sulphur might be tolerated. Several large companies use a limestone with 4-15 % magnesia as a flux, although a purer limestone, if it were available at thesame cost as that being used, would contribute to a more efficient process. Similarly, for basic open-hearth smelting, the flux should be ideally at least 98% CaC03 with only 2 % of impurities such as alumina, silica and magnesium carbonate and but a trace of phosphorus; however, in areas where the purer material is not available, the flux might contain 5-10% magnesium carbonate, 1.5 % alumina and 1 % silica. The capacity for phosphorus removal is lessened by the higher magnesia content, and more flux must be used. Transportation costs involved in bringing a purer fluxing agent from a distant area, however, would cut profit margins so that the less efficient material is employed in many cases. Table XXI contains individual and composite analyses of selected carbonate rocks. There does not exist a standard list of components that should be determined in the chemical analysis of a carbonate rock. The analyses that are made are dependent, in some cases, upon the needs of the person requesting them and, in others, by the availability of facilities and equipment. Some of the differences in the type of compounds reported as part of a carbonate analyses are demonstrated in Table XXI. An obvious difference can be found in the method of reporting the loss on ignition in weight percent. Some laboratories equate this percentage with the COZ content of a carbonate rock, but investigations made by GALLE and RUNNELS (1960) and WAUGHand HILL(1960) demonstrate that this is not so. By accurately controlling the temperature of a muffle furnace at 550°C and l,OOO"C, values of the loss on ignition were obtained for carbonate and non-carbonate portions. In samples which contain small amounts of pyrite, the loss on ignition is complicated by the oxidation of the pyrite. Upon oxidation, the pyrite forms Fez03 and oxides of sulphur, which in turn react with CaC03 below the intermediate temperature to form CaS04, and thus cause a premature evolution of COZ. It is possible to obtain a true COa value by applying corrective measures as outlined by WAUGHand HILL(1960). It is evident that the results of a chemical analysis, however technically perfect, are representative of a carbonate rock only in so far as the sample supplied to the analyst is representative of the unit being studied. GALLE (1964) has shown that on samples taken along an outcrop, channel samples give more reliable and consistent analytical results than spot samples, and indicated that analyses of carbonate rock to be presented to a possible user should be made on channel samples. CLARKE (1924) gave an extensive listing of chemical analyses of carbonate rocks. GRAF(1 960a) presented tables of isotopic compositions and chemical analyses of carbonate rocks and sediments and of minor element distribution in

TABLE XX SOME PHYSICAL PROPERTIESOF SELECTED CARBONATE ROCKS~

Rock type

Location ASG

AP

CS

limestone (fossiliferous) limestone limestone (coarse white) limestone (kerogenaceous) limestone limestone limestone limestone limestone (chalky-smokey Hill-dry limestone (chakySmokey Hill) limestone (chalkyFort Hays-dry) limestone (metamorphic) limestone limestone (fossiliferous, oolitic) dolomitic limestone dolomitic limestone dolomitic limestone dolomitic limestone dolomitic limestone, glauconitic

Ind.

2.37

11-

10.9

1.6

1.9

3

27

4.84 2.06

3 12.4

WINDES(1949)

Ohio Ala.

2.69 2.83

28.5 24.0

2.9

8.6 6.6

10 7

58 66

7.97 3.64 7.64 3.51

4 15.4 4 14.2

WINDES (1949) WINDES(1949)

Colo.

2.25

16.6

0.4

3.7

10

56

1.8

1.0

22 7.8

WINDES (1949)

Utah

Ohio Ill. S. D.

2.78 2.68 2.6 2.68 1.71

28.0 23.0 8.0 22.3 2.4

2.2 1.9 13 2.6 0.3

2.5 2.5 1.5 3.0

9.3 9.6 2.6 7.4

52 61 33 52 13

9.43 9.56 4.2 9.87 0.65

3.93 3.96 2.0 3.84 0.37

2 3 4 3 10

WINDES (1950) WINDES(1950) WINDES (1950) BLAIR(1955) BLAIR(1955)

S. D.

2.0

2.0

0.3

10

0.75 0.5

S.D.

1.81

3.7

0.6

1.2

16

0.98 0.57

Calif.

2.80

15.3

0.6

3.2

42

4.51 2.15

7 10.9 0.05 BLAIR(1955)

Mo.

Okla.

2.67 2.56

1.2

18.9 16.8

2.0 2.3

3.1 2.9

8

59 41

6.49 2.66 7.45

6 13.5 0.24 BLAIR(1956) 0.20 BLAIR(1956)

Ohio Ohio Ohio Mo. Mo.

2.5 2.5 2.8 2.69 2.67

6.4 5.2 1.3 2.6 3.6

13 12 26 28.8 21.2

17 22 28 2.7 1.5

2.1 2.0 4.0 4.8 4.2

3.7

30 6.1 36 6.8 55 9.5 33 11.1 48 5.61

w. v.

0.7 0.9

0.26 6 2.7 0.8 26.0

8.3

TS

58

MRupIT

AH SH Y M

4.0

7.2 8.0 7.2

MRig SDC L B V P R

2.6 2.8 4.1 4.55 3.05

15.9-0.12 16.4 0.21 11 0.06 16.5 0.28 5.7 0.13

Reference

DWALLand ATCHINSON (1957) 13 6.3-0.13 BLAIR(1955) 5.0

7 10 4 3 >11

14 0.19 14 0.23 16 0.16 17.6 0.22 12.4-0.07

WINDES(1950) WINDES (1950) WINDES(1950) B~~m(1955) BLAIR(1955)

7

P

dolomite dolomite (gray) dolomite (siliceous) dolomite dolomite dolomite dolomite dolomite marble marble (white) marble limestone and marble marlstone (calcareous and dolomitic) limestone

Tenn. Tenn. Tenn. Ohio Ohio Ohio Ohio Ohio Md. Nev. N. Y. Nev. Colo.

2.84 2.76 2.77 2.4 2.6 2.6 2.6 2.4 2.87 3.2 2.72 2.79 2.31

0.7 2.3 1.2 8.6 3.4 4.0 3.0 8.5 0.6 2.3 1.8 0.4 4.9

46.7 52.0 35.6 13 23

3.8 3.8 2.5 11 19 14 14 14 2.8 2.4 1.7 2.6 1.8

15

19 11 30.8 34.5 18.4 22.3 21.9

marble

1.87-2.80 1.1-31.0 2.62.8 2.64-2.87 0.4-2.1 8-27

limestone dolomite marble limestone limestone marble (dolomitic)

2.66 2.70 2.63 2.34 2.56 2.80

5.9 14 7.1 13 4.6 11 1.8 3.4 2.7 7.3 1.9 6.4 2.3 7.8 2.1 4.2 2.7 8 3.0 3.9 4.3

7 9 6.7

427- 0.5-2 7ea 1-24 853 427- 0.6-4 6ea 8 4 2 1280 8 26 9 25 6 47

2.5-28.4 16.5 700 22 950

74 12.3 69 11.3 66 10.9 42 2.8 56 6.7 53 4.1 58 6.9 39 3.2 56 7.15 11.9 49 7.84 54 11.4 56 3.61

5.1 4.6 4.62 1.55

3.2 2.0 2.9 1.5 3.78 5.02 3.35 4.54 1.61

2 17.9 3 17.4 2 17.0 5 9.0 -0.09 5 14 0.05 6 11 0.03 3 14 0.18 4 10 0.07 4 13.7 4 16.6 3 14.5 1 17.4 14 10.5 0.11

1.2-3

*z

U

c,m m

TREFETHEN (1959)

4.35- 0.8-3.6 8.7 7.25- 1.3-6.5 10.15

3-6 7.6 12

WINDES (1949) WINDES (1 949) WINDES (1949) WINDES (1950) WINDES (1950) WINDES(1950) WINDES (1950) WINDES(~~~O) WINDES(1 949) WINDES (1949) WINDES (1949) WINDES (1949) WINDES(1950)

TREFETHEN (1959)

15

18

WCOLF(1953) WCOLF(1953) WOOLF(1953) KESSLERand SLIGH(1927) ATCHISON et al. (1962) ATCHISON et al. (1962)

Legend: ASG= apparent specific gravity; AP= apparent porosity (%); CS= compressive strength (1,OOO Ib./sq. inch); TS= tensile strength (1,OOO lb./sq. inch); MRup= modulus of rupture (1,OOO Ib./sq. inch); IT= impact toughness (inch/sq. inch); AH = abrasive hardness (10-3 resistivity x sq. inch/lb.); SH= scleroscope hardness (scleroscope units); YM= Young’s modulus? (106 Ib./sq. inch); MRig = modulus of rigidity (106 Ib./sq. inch); SDC= specific damping capacity ( x lod2);LBV= longitudinal bar velocity (1,OOO ft./sec); PR= Poisson’s ratio (dimensionless).

W

m w

TABLE XXI SELECTED COMPOSITE AND INDIVIDUAL CHEMICAL ANALYSES OF CARBONATE ROCKS

I talc. CaC03 calc. MgC03 CaO MgO

42.61 7.90 41.58

coz

1.o.i. d.1.o.i. (lO5/55OyC) d.1.o.i. (550/1,OOO"C) SiOz A1 2 0 3 Fez03 FeO acid. insol. Fe MnO MnOz

5.19 0.81

} 0.54

Ti02

KzO NazO Liz0

sos

S FeSz Pzos HzO (-) HzO (+) carbonaceous material SrO F

2

41.32 2.19 33.53 (34.55) 14.11 4.16 1.63

3

4

5

6

7

8

9

10

80.83 89.78 86.39 79.86 70.10 2.26 1.33 1.94 1.39 3.96 53.81 45.44 50.40 48.49 43.01 42.92 54.84 1.68 1.09 1.29 1.03 0.42 0.26 0.56 35.36 43.26 42.69 1.34 0.75 0.89 1.12 36.73 40.17 38.93 34.44 8.47 4.67 7.08 14.45 1.91 0.81 1.22 2.32 3.71 1.16 1.55 2.46 0.14

0.29

0.13

0.14

1.36 1.14 15.05 0.18 9.02 0.20 ),.I' 1.27

0.05

0.038

0.06 0.33 0.05 trace 0.05 0.09

0.16 0.71 0.39

0.08 0.25 0.07

0.05 0.07 0.02

0.07 0.12 0.04

0.18 0.39 0.10

0.04 0.25

0.03 0.02

0.04 0.06

0.03 trace 0.04

0.04 0.15 0.21(110"C) 0.56l 0.61 0.12

0.09

0.10 0.26 0.49 0.03

1.15 0.45

0.26

} 0.07

0.05 0.08 )19.03

0.09

0.23 0.69

4

Hz

vzos total

100.09

99.40

99.96 99.87 99.96 99.79 99.47 100.00 99.40 99.91

I Composite analysis of 345 limestones (CLARKE,1924). 2 Argillaceous limestone standard sample la, U.S. Natl. Bur. Std., dried at 105°C (NATIONAL BUREAU OF STANDARDS, 1954). 3 Composite analysis of 32 channel samples of the Toronto Limestone member of the Oread Limestone Formation, Pennsylvanian age, eastern Kansas, taken along the strike of the outcrop from the Nebraska border on the north to the Oklahoma border on the south (0.K. Galle, W. N. Waugh and W. E. Hill Jr., personal communication, 1964). Used for riprap, rubble. 4 Composite analysis of 32 channel samples of the Leavenworth Limestone member of the Oread Limestone Formation, Pennsylvanian age, eastern Kansas, taken along the strike of the outcrop from the K. Galle, W. N. Waugh and Nebraska border on the north to the Oklahoma border on the south (0. W. E. Hill Jr., personal communication, 1964). 5 Composite analysis of 32 channel samples of the Plattsmouth Limestone member of the Oread Limestone Formation, Pennsylvanian age, eastern Kansas, taken along the strike of the outcrop from the Nebraska border on the north to the Oklahoma border on the south. Used for aggregate, road metal, agricultural limestone (0.K. Galle, W. N. Waugh and W. E. Hill Jr., personal communication, 1964). 6 Composite analysis for 25 channel samples of the Kereford Limestone member of the Oread Limestone Formation, Pennsylvanian age, eastern Kansas, taken along the strike of the outcrop from the Nebraska border on the north to the Oklahoma border on the south (0.K. Galle, W. N. Waugh and W. E. Hill Jr., personal communication, 1964). Used for flagging. 7 Medway white chalk, Great Britain (JOHNSTONE and JOHNSTONE, 1961). Used for Portland cement manufacture. 8 North Wales limestone, Great Britain (JOHNSTONE and JOHNSTONE, 1961). Used for Portland cement manufacture.

365

PROPERTIES AND USES OF THE CARBONATES

12

I1

54.70 0.60 41.70 (43.00) 0.40 0.52 0.08

30.49 21.48 47.25 (47.52) 0.31 0.067 0.084

13 55.41 43.00

0.63 0.70

0.006

14

15

31.20 53.54 20.45 1.02 47.87

29.9 9.9 30.3

43.27 1.57 0.40 0.24

33.8 17.7 2.5 1.1

0.11 0.30 0.19

016

0.06

0.05 0.27

0.035 0.013

0.007

0.003

99.94

43.92

0.10

0.14 0.08

9.07 4.43 0.85 0.93 (0'54

1

0.1

0.9 0.8

0.04

0.05 0.16 0.14

0.007 2.6 0.006(105"C) )o.6

0.09 1.39

J

99.95 100.18 100.08

19

94.39 0.61 51.09 42.75 53.03 0.93 1.46 0.29 34.62 7.57 41.56

0.69

0.08 <0.01

99.78

18

I .O

0.008

~

17

0.18

0.02

0.005 0.03 0.08

trace

16

calc. CaC03 calc. MgCo3 CaO MgO

coz

1.o.i. d.1.o.i. (l05/55O0C) d.1.o.i. (55O/1,OOO0C) SiOz A1203 Fez03 FeO acid. insol. Fe MnO MnOz Ti02 KzO NazO Liz0

so3 S

FeSz

PZOS

0.3

HzO (-) HzO (+I carbonaceous material SrO F

0.1

vzos

2.9

100.7 96.30 99.95 99.85

Hz

total

-

9 Typical cement rock, Bethlehem, Penn. (ECKEL,1913). 10 Lithographic limestone, Solnhofen, Bavaria (CLARKE, 1924). I1 Spergen Formation (oolitic Salem Limestone), Mississippian age, Indiana (LOUGHLIN, 1930). Used for building stone. 12 Dolomite standard sample 88, U.S. Natl. Bur. Std., dried at 105"C (NATIONAL BUREAU OF STANDARDS, I#954). 13 Ketona Dolomite, Cambrian age, Alabama (BALLand BECK,1938). Used for fluxstone and a source for magnesia. 14 Niagara Dolomite, Silurian age, Illinois (LAMAR, 1960). Used as a refractory and for dead-burned dolomite. I5 Composite analysis of 10 channel samples of the Baum member of the Paluxy Formation, Lower and HAM,1955). Cretaceous age, Oklahoma (WAYLAND 16 Composite of 15 analyses of the Meade Peak member of the Phosphoria Formation, Permian age, Wyoming (GULBRANDSEN, 1958, compiled from MCKELVEY et al., 1953). 17 Composite of 8 analyses of the Marble Falls Formation, Pennsylvanian age, Texas (BARNES, 1952). 18 Composite analysis of 9 mark from Minnesota lakes (GOLDICH et al., 1959). Total loss on ignition less COZand HzO (-) 19 Limestone from Maquijata, Province of Santiago del Estreo, Argentina (GAMKOSIAN et al., 1961).

Includes organic matter.

366

P. R. SIEGEL

these materials (GRAF,1960b). Several analyses have also been presented by GILLISON (1960a,b). INCERSON (1962) noted that compilations of carbonate rock analyses were being made at least at two places: H. R. Gault began such a compilation at Lehigh University and his program is being continued by K. Chave. The collection of analyses of all types of sedimentary rocks was begun by W. W. Rubey of the U.S. Geological Survey and continued by H. A. Tourtelot, who reports (personal communication, 1964) that for Kansas, Nebraska, North Dakota, South Dakota, Montana, Wyoming, and Colorado, it had already been completed. Other properties

The number of measurable properties of carbonate minerals is great (see GRAFand LAMAR,1955) and is increasing as systematic advances in theory and instrument technology are made (e.g., electron-spin resonance, nuclear magnetic resonance, Mossbauer effect, microwave, and exo-electron emission studies). Some of the properties of a physical-chemical nature are summarized in Tables XXII-XXIV. For the most part, the data given are for pure compounds, and as noted previously, properties will vary with the presence of impurities. Among the properties most affected by the presence of foreign ions in the crystal lattice are thermoluminescence, infrared absorption, and those properties related to solid solution. Solid solution and subsolidus relations Much of the initial impetus for these studies was provided by GRAFand GOLDSMITH (1955) and HARKER and TUTTLE (1955) who investigated the solid solution and subsolidus relations in the system CaC03-MgC03. It was found that the percentage of Mg in calcite could be determined from various cell parameters (e.g., dioia, a or c). Similar results were given by CHAVE(1952), who found a linear variation in the dloia spacing with varying percentages (2-1 6 %) of MgC03 in shell material from living organisms. At the elevated temperatures and pressures used by HARKER and TUTTLE (1955), the solubility of MgC03 in CaC03 increased from 5 mol: % at 500°C to 27 mol. % at 900°C. Corroborating figures were given by GRAFand GOLDSMITH (1955). Because of these and similar relations, it was suggested that when a rock contains dolomite in equilibrium with magnesian calcite, the amount of solid Solution can be used as a geologic thermometer. Harker and Tuttle also found that at 900"C, dolomite will take only 1 % excess MgC03 in solid solution indicating that the miscibility gap in the system CaC03-MgC03 is almost complete and that at this same temperature magnesite would take only about 2 % (by weight) CaC03 into solid solution. GRAF(1960c), citingunpublished data of Goldsmith, wrote that at 800°C dolomite will hold 2 mol. %excess CaC03 in solid solution and that this would increase to 4 % at 900°C. GOLDSMITH and GRAF(1958a) were able to determine the mole percentage of CaC03 in dolomites from various rocks by X-ray diffraction techniques.

TABLE XXII MELTING AND TRANSFORMATION TEMPERATURES AND SOLUBILITIES OF SOME ECONOMICALLY IMPORTANT CARBONATE MINERALS

(Melting and transformation temperatures after KRACEK, 1963; solubilities after PERRY et al., 1963) Mineral

Melting point

Dissociation temperature

Transition point

*2: ' s

v1

Solubility in 100 g

H20

m

calcite dolomite

1,339"C(at 1,038 bars C02 pressure)

strontianite cerussite malachite azurite trona

970 "C

at 500°C and 1 atm COZ pressure, dolomite+CaCOs+ MgOSCOZ at 89OoC, dolomite-tCaO Mg0+2C02 404°C (at 1 atm COz pressure) 369 "C (at 1 atm C02 pressure) 450°C (at 1 atm C02 pressure) 3oO-400"C (at 1 atm C02 pressure)

1,740"C (at 90 atm C02 pressure) 1,497"C (at 60 atm C02 pressure)

195°C

1,204"C (at 0.068 atm C02 pressure) 1,352"C (at 1 atm CO2 pressure) 1,091"C (at 0.152 atm COZpressure) 1,289"C (at 1 atm CO2 pressure) 293°C (at I atm COZpressure) 200 "C 200 "C

b5

0.0014 (25°C)

%

0.032 (1 8 "C)

8

1

n

z-

+

magnesite rhodochrosite siderite smithsonite aragonite witherite

898.6"C

0.0106 0.0065 (25°C)

to calcite at about 425°C and 1 atm pressure 806"C, 968 "C 925°C

0.001 (15°C) 0.0012 (20°C) 0.0022 (1 8 "C) 0.0011 (18°C)

o.oO011 (20°C)

0 2:

5

E

TABLE XXIII HEATS OF FORMATION, FREE ENERGIES OF FORMATION AND HEAT CAPACITIES OF SOME ECONOMICALLY IMPORTANT CARBONATE MINERALS'

Heat of formation Fret' energy Of formation at 25"C, kcallmole at 2jaC9kcallmole (2) A F AH (I)@

Heat capacity at constant Range of temp. pressure (T='K; O"C=273.1 OK), ( O K ) (calldegree mol)

calcite dolomite magnesite rhodochrosi te siderite smithsonite aragonite witherite

-289.5 -558.8 -261.7 -21 1 -172.4 -192.9 -289.54 -284.2

-270.8

19.68+O.O I 189T-307600/Tz 40.1 16.9 7.79 +OM2 1T +0.0000090T2 22.7

strontianite cerussite malachite azurite

-290.9 -167.6

-271.9 -150.0

-241.7 -192.5 -154.8 -173.5 -270.57 -271.4

-269.78 -520.0 -246.0 -195.4 -161.06 -174.8 -269.53 -272.2 -271.9 -149.7 -216.44 -373.73

a 17.26+0.0131T

30.0 21.8 21.1

Uncertainty

( %)

273-1 033 299-372 290 273-773 293-368 273-1083 1,083-1 255 281-371 286-320

5

15 ? ?

1 Heats of formation, free energies of formation (I)and heat capacities, compiled from LILEY et al. (1963); free energies of formation (2) compiled from CARRELS et al. (1960).

crl

P

369

PROPERTIES A N D USES OF THE CARBONATES

TABLE XXIV MAGNETIC SUSCEPTIBILITIES OF CERTAIN CARBONATE MINERALS

(Compiled from POWELL and MILLER,1963) Mineral

Location

calcite calcite dolomite dolomite dolomite dolomite dolomite dolomite magnesite magnesite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite siderite rhodochrosite smithsonite smithsonite aragonite witherite strontianite cerussite cerussite limestone

Joplin, Mo. not given Cumberland, Great Britain Guanajuato, Mexico Westchester Co., N.Y. Berkshire Co., Mass. not given not given Regla, Cuba Lancaster Co., Texas Roxbury, Conn. Allevand, France not given not given Kellogg, Idaho Saline Co., Ark Rhine Province, Germany Saline Co., Ark. Saline Co., Ark. Los Angeles Co., Calif. Leadville, Colo. Cass Co., Texas Pulaski Co., Ark. Clairborne Parish, La. Pulaski Co., Ark. Rogers Co., Okla. Bates Co., Mo. Roxbury, Conn. not given Mineral Point, Wisc. Kelly, N.M. not given Cumberland, Great Britain not given New South Wales, Australia New South Wales, Australia not given

1x= 1

*

10-6 cgs electromagnetic units.

12

- 0.384 156 73 51 42 42 0.993 83 17 499 492 103.8 103.7 91.5 90.8 87.3 85.8 84.2 83.2 81.5 77.2 75.4 12.5 72.1 66.6 66.2 66.1 no value given 17 14 - 0.408 4 no value given 65 23 6

370

F. R. SIEGEL

The most comprehensive study on the properties of the calcium and magnesium carbonates was presented by GRAFand LAMAR(1955), with a bibliography of 524 references. Further advances in understanding this CaC03-MgC03 system were made by GOLDSMITH and GRAF(1958a) who published data on structural and compositional variations in some natural dolomites, as well as on the relation between lattice constants and composition in the Ca-Mg carbonates (GOLDSMITH and GRAF, 1958b). More recently, ROSENBERG and HOLLAND(1963) gave a preliminary report on the stability of calcite, dolomite, and magnesite in chloride solutions at elevated temperatures and COa pressures. The solid solution relations existing between calcite and rhodochrosite were reported on by GOLDSMITH and GRAF(1957). They have shown experimentally that a complete series exists above 550°C at COZpressure sufficient to prevent decomposition, but that there is a solubility gap at lower temperatures in the manganese half of the system. BODINE and HOLLAND (1963) have provided additional data on the coprecipitation of manganese with calcite at elevated temperatures to complement data presented by GOLDSMITH and GRAF(1957), who were able to precipitate the complete Ca-Mn carbonate solution series at room temperature. ROSENBERG and HARKER (1956) worked on the subsolidus phase relations in the CaC03-FeC03 system and found a miscibility gap between calcite and siderite at temperatures from 350-550°C. Experiments run at COZpressure high enough to prevent dissociation showed that a solid solution of 5 mo1.X siderite in calcite is stable at 400°C and that at 5OO0C, about 14 mo1.x siderite can be taken into solid solution by calcite. Under similar COZpressure conditions, GOLDSMITH (1959) reported that a solid solution of up to 8 mol. % siderite in calcite is stable at 400°C and at 700°C this increases to 37 mol. %. In a more recent study at elevated temperatures (ROSENBERG, 1963) (using small CO partial pressure to maintain iron as Fez+), a solvus between CaC03 and FeC03 was determined between 300 and 550°C. With COe pressures sufficient to prevent dissociation of the carbonates, solid solutions containing up to 9 mo1.x siderite in calcite and 7 mo1.X calcite in siderite were stable at 400°C. At 500°C the solvus passed through a point at 17 mol. % siderite in calcite. Related studies on ternary systems have been made. GOLDSMITH and GRAF (1960) investigated the subsolidus relations in the system CaC03-MgC03-MnC03 in the temperature range of 5O0-80O0C, with special emphasis being given to the CaMg(C03)2-CaMn(C03)~ join; above 650 "C, a complete solid solution series extends between the two members. In his work on the system CaC03-MgC03-FeC03, particularly on the join CaMg(C03)2-CaFe(C03)2, ROSENBERG (1959) found that at 450°C this join is binary from CaMg(C03)~to 75 mo1.X CaFe(CO3)z. GOLDSMITH et al. (1962) studied the phase relations in this same system at temperatures ranging from 600 to 800°C and 15 kbars total pressure. More recently GOLDSMITH and NORTHROP (1 964) have reported the results of

PROPERTIES AND USES OF THE CARBONATES

371

their research on the subsolidus phase relations in the ternary systems CaC03MgC03-CoC03 and CaC03-MgC03-NiC03. Although emphasis has been on the minerals of the calcite or dolomite groups, CHANG(1964a) worked on the subsolidus phase relations in the binary systems BaC03-CaC03, SrC03-CaC03, and BaC03-SrC03 between 400 and 1,OOO”C and at C02 pressures high enough to prevent decomposition of the carbonates. He observed that for the system BaC03-CaCO3, there is a complete solid solution above 850°C; at 400”C, CaC03 was 3.5 mol. % soluble in BaCOs; and at 700”C, 5 mol. % soluble. The maximum amount of calcium taken up by SrC03 is about 47 mol. % at 550°C.

-

Thermoluminescence Certain minerals possess the ability to store energy in the form of electron energy. An electron, displaced by some external source of energy such as natural a radiation, can be moved from its normal lattice position and become “trapped” by some type of imperfection in the crystal lattice structure. Some of the common types of possible electron traps are described by DANIELS et al. (1953): ( I ) imperfections and vacancies in the crystal lattice produced at the time of crystal formation, or later by mechanical stress or thermal agitation; (2) lattice vacancies (Schottky defects); (3) distortions produced by impurity ions of larger or smaller radius than is normal in a given crystal lattice; and (4) dislocations produced by radioactive bombardment. In addition, Frenkel defects, which are produced when an atom is transferred from a lattice site to an interstitial position, can serve as electron traps (KITTEL,1956, chapter 17); and color centers (F, F’, R and N centers) may act as traps for electrons, whereas V centers may act as traps for holes (KITTEL,1956, chapter 18). Any excess energy associated with the electron becomes “frozen” in the trap; when released by the application of heat, the excess energy is dissipated in the form of heat and light. The light thus produced is termed thermoluminescence. The frontispiece (p.VI) shows calcite crystals that were photographed by their own thermoluminescence. These crystals were subjected to approximately 2 106 Roentgens of y-radiation from 6OCo. They were then heated on a standard laboratory electric hot plate to 300°C in a completely dark room and the photographic exposures were made. Both the rhombohedra1 and scalenohedral crystal forms give the orange luminescence characteristic of calcite. The photographs were prepared by H. K. W. Bowers, using Ektachrome Daylight film and an exposure time of 1+ min. This technique for obtaining excellent representations of mineral thermoluminescence was developed by Mr. Bowers as part of a radiation damage research project supported by the U. S. Atomic Energy Commission (contract no.AT( 11-1)-1057), with Dr. E. J. Zeller being the principal investigator. The thermoluminescence of calcite, aragonite, dolomite, and magnesite has been studied by many workers and attempts have been made to use observed

-

372

F. R. SIEGEL

effects in solving certain geologic problems involving carbonate rocks. For example, limited success was achieved in correlation and zonation of carbonate sediments by PARKS(1953), SAUNDERS (1953), BERGSTROM (1956), LEWIS(1956), and BROOKS and CLARK(1961), whereas SIEGEL(1963) was able to relate artificially induced thermoluminescence of sedimentary dolomites to their probable environment of deposition. ZELLER(1957), PEARN(1959), D’ALBISSIN et al. (1962), and ZELLER and RONCA(1963) have applied thermoluminescence techniques to direct age determinations and the dating of tectonic and thermal events. Temperature (including paleoclimatology) and pressure histories of carbonate rocks have been revealed by thermoluminescence investigation (ZELLER,1957; ANGINO,1961 ; Ronca, 1964). HANDINet al. (1957) have used thermoluminescence in deformation studies of calcite and dolomite, as have ROACHet al. (1961) in their investigation of the effects of impact on marble. Geochemical prospecting using thermoluminescence has been reported by MACDIARMID (1960a, b). The above represent only a fraction of the studies made using thermoluminescence. ANGINOand GROGLER (1 962) have compiled an extensive bibliography of thermoluminescence regearch containing more than 600 entries. This is an excellent reference work for scientists intending to do thermoluminescence research on carbonates and other rocks. Infrared absorption spectra HUANGand KERR(1960) described the infrared spectra of 27 common and rare carbonates and found that each one shows characteristic absorption bands, some of which differ from published curves. In the calcite and the aragonite groups there was a noteworthy shift of absorption bands with longer wave lengths, which corresponds to an increase in cation radius or mass, a phenomenon also et al. (1 952). HUANGand KERR(1960) believed that the specobserved by KELLER tral difference between the more common groups may be related to crystal structure and that infrared-active groups (CO32-, HCOs-, HzO, OH-, and so42-) dominate the absorption characteristics. Although the emphasis of infrared studies has been on mineral identification (Table XXV), ADLERand KERR(1962) began applying the method to geologic problems. In a detailed study on aragonite and calcite, they found that in artificial mixtures, the intensity ratio of the bands at 11.41,~(specific for calcite) and 11.65,~ (specific for aragonite) is approximately proportional to the ratio of concentration of aragonite and calcite in a given sample. This relation held for recent and fossil invertebrates and suggested application of the method to the study of the composition of calcareous shells. Later empirical studies of infrared absorption spectra of isomorphous, anhydrous carbonate minerals (ADLER and KERR,1963)demonstrated that shifts in the frequencies of carbonate-ion vibrations are primarily related to differences in the radius of cations in the external lattice positions. They believed that this relationship may be conditioned by the electronic periodicity of the cations; and although mass effects are suggested, they are not definitely shown. In addition,

PROPERTIES AND USES OF THE CARBONATES

373

they interpreted spectral differences among the calcite group and aragonite group minerals in terms of co-ordination change between the two groups and the mineral composition within each group. ADLER(1963) presented some basic considerations in the application of infrared spectroscopy to mineral analysis. He affirmed that the infrared absorption spectra may be used in various ways to gain information on minerals and mineral aggregates, such as composition, structure, and mode of combination of molecular ions (anionic radicals) in unidentified materials.

USES

The most recent compilation of uses in which the carbonate rocks are employed directly (e.g., dimension stone) or indirectly in a manufacturing process (e.g., glass manufacture or sugar refining) was made by LAMAR (1961). In this paper, Lamar gave more than 70 uses for limestone and dolomite, and general physical and/or chemical specifications for each use; he also included an excellent bibliography of 156 entries. Similar presentations have been made by other authors. JOHNSTONE and JOHNSTONE (196 1) wrote about minerals for the chemical and allied industries, with a chapter devoted to limestone, chalk, and whiting; carbonates are also considered in separate chapters on iron ores, lead, magnesium, manganese, sodium carbonate, and strontium. These authors included many British and Canadian specifications in addition to the American Society for Testing and Materials requirements. In the American Institute of Mining, Metallurgical, and Petroleum Engineers (1960) edition of Industrial Minerals and Rocks (Nonmetallics other than Fuels), GILLISON (1960a,b) treated physical and chemical properties of the carbonate rocks and discussed some of the uses for limestone and dolomite. This fine symposium also contains chapters on specific carbonate products (e.g., cement materials, chalk and whiting, crushed stone, dimension stone, lime, magnesite and related materials, mineral fillers, refractories, sodium carbonate from natural sources in the United States, and strontium minerals). GAMKOSIAN et al. (1961) listed the chemical specifications of carbonate rocks to be used for specific industries of Argentina; it was noted that Gamkosian is preparing a publication entitled Technologia Mineral, in which he will present various physical and chemical requirements followed not only in the Argentine Republic, but probably also in other republics of Central and South America. Previous to this surge of publications in 1960 and 1961, BOWLES (1956) summarized many uses for limestone and dolomite, bringing up to date earlier publicgions of the U. S. Bureau of Mines by BOWLES (1952) on the lime industry, by BOWLESand JENSEN (1947) on the industrial uses for limestone and dolomite, by BOWLESand JENSEN (1941) on limestone and dolomite in the chemical and processing industries, and by COLBY(1941) on the occurrence and uses of dolomite in the United States.

w

TABLE XXV

2

INFRARED ABSORPTION BANDS OF SOME ECONOMICALLY IMPORTANT CARBONATE MINERUS

(Compiled from HUANG and KERR,1960, and ADLERand KERR,1963) Mineral

Position of absorption bands; wavelength ( p )

calcite

3.93 5.52 6.97 3.92 5.50 6.97

dolomite

rhodochrosite

3.95 5.50 6.90 6.95 6.97 5.50 6.90 6.86 6.94 3.95 5.52 6.98

siderite

3.95 5.50

smithsonite

3.95 5.47 6.95

aragonite

3.95 5.55

magnesite

7.02 7%5

7.07 7.09 7.03 7.06 7.08

7.04 7.06 6.70-7.00 9.22

3.95 5.55 6.72

9.22

3.93 5.53 6.70-7.00

9.22

6.80

11.42 11.40 11.40 ir.41 11.35 11.35 11.35 11.28 11.28 11.29 11.53 11.54 11.55 11.55 11.53 11.55 11S O 11.48 11.50 11.42 11.63 11.40 11.63 11.42 11.63 11.65

Reference

13.70 13.72 13.71 13.36 13.35 13.35 13.76 13.75 13.77 13.58 13.54 13.58 . 13.45 13.42 13.45

14.03 14.02 14.02 14.03

HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) ADLERand KERR(1963) HUANG and KERR (1960) ADLERand KERR(1963)

14.03 14.30 14.03 14.30 14.03 14.30 14.02

HUANGand KERR(1960)

I" 0

ADLERand KERR (1963)

Y

8P

v 6.79

witherite

4.00

5.65

strontianite

3.97

5.57

5.75

cerussite malachite

2.85

azurite

2.84

5.40

trona

2.83

5.92

11.64

6.92 6.97 6.99 6.80

9.40

11.63 11.63 11.62 11.63

9.30

6.88

11.65

6.86

11.65

6.95 6.62 6.63 6.78 6.80

14.31 14.04 14.31 14.43 14.41 14.41 14.15 14.30 14.16 14.31 14.14 14.29 14.77 14.75 14.75 14.05

7.13 7.17 7.18 7.00 7.17 7.03

9.48 9.10 9.52 9.15 9.45 9.65

11.90 11.90 11.92 11.45 10.47

11.97 11.75

12.17 12.90 12.23

13.33 13.00

E HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) ADLERand KERR(1963)

14.70

a.

12 d

E HUANGand KERR(1960) ADLERand KERR(1963) HUANGand KERR(1960) HUANGand KERR(1960)

13.45

b!$

HUANGand K E R(1960) ~

c,

$

82. 5 12

376

F. R. SIEGEL

The US.Bureau of Mines annual publication, Minerals Yearbook, Volume I , (Metals and Minerals except Fuels) gives an excellent review of carbonate rocks and materials derived from them (e.g., calcium and calcium compounds, cement, lime, magnesium, magnesium compounds, manganese, sodium and sodium compounds, stone, and strontium). Major uses are also listed along with pertinent production and dollar statistics. This volume also includes data on production increases (or decreases) for given uses, and makes note of the development of technological advances or new products which affect carbonate (and other) rock economics. The Bureau of Mines has a materials survey project under way; and in 1963, COMSTOCK treated magnesium and magnesium compounds in great detail and listed the principal uses for magnesium compounds (derived in part from dolomite and magnesite), as given in Table XXVI. Table XXVII gives more than 100 uses for limestone, dolomite, marble, precipitated calcium carbonate, or products derived from them (e.g., lime). The (1961) paper and is supplemented by the table is constructed on a base of LAMAR’S TABLE XXVI PRINCIPAL USES FOR MAGNESIUM COMPOUNDS

(After COMSTOCK,1963) Magnesium oxide

Precipitated magnesium carbonate

Refractory grades: basic refractories Caustic-calcined: cement rayon fertilizer insulation magnesium metal rubber fluxes refractories chemical processing and manufacture uranium processing paper processing U.S.P. and technical grades: rayon rubber (filler and catalyst) refractories medicines uranium processing fertilizer electrical insulation neoprene compounds and other chemicals cement

insulation rubber, pigments, and paint glass ink ceramics chemicals fertilizers Magnesium hydroxide sugar refining magnesium oxide pharmaceuticals Magnesium chloride magnesium metal cement ceramics textiles Paper chemicals

377

PROPERTIES AND USES OF THE CARBONATES

20 18

I6 14

600 12

550

10

450

1955 '56

u '58 '59 '60 '61

'62 '63 '64

8 6 1954 '55 '56 '57

'58 '59 '60 '61 '62 '63 '64

Fig.2.

Fig. 1 .

Fig.1, U.S. crushed stone production (in millions of tons). Printed by permission of Rock Products (Mining and Processing), January, 1964. Fig.2. U.S. lime production (in millions of tons). Printed by permission of Rock Products (Mining and Processing), January, 1964. 400 390 380 370 360

350 340 330 320 310

3m

1955 '56 5 7

'58 '59 '60

'61

'62 '63 '64

Fig.3. U.S. Portland cement production (in millions of barrels). Printed by permission of Rock Products (Mining and Processing), Januaiy, 1964.

sources already mentioned as well as trade magazines such as Rock Products or Rock Products (Mining and Processing) (name changed with the January, 1964, number). Several of the derivatives of the carbonate rocks (such as whiting or lime) have multiple uses; to give the reader an idea of the magnitude of applications a single derivative can have, the various uses in which and for which whiting is used are presented in Table XXVIII. In some reviews of carbonate economics, the uses of carbonate minerals are neglected. Such data are readily available in most mineralogy and economic geology textbooks and other not so widely known reference works such as those by STECHER (1 960) and LANGE (1 956). In Table XXIX, some of the more important uses for natural or artificially prepared carbonate minerals are summarized. The future looks good for the continued development of the major industries in which carbonate rocks are a primary raw product. Trends in the U.S.production of crushed stone, lime, and Portland cement (Fig.1, 2, and 3, respectively) are all

w

TABLE XXVII

4

00

PURPOSES FOR WHICH LIMESTONE AND DOLOMITE (OR LIME DERIVED FROM THEM) ARE USED (WITH SOME GENERALSPECIFICATIONS)

(Constructed on a base of the report by LAMAR,1961, and supplemented by data from BOWLES and JENSEN,1941, 1947; COLBY,1941; BOWLES, 1952, and JOHNSTONE,1961; and ANONYMOUS, 1963) 1956; BOWEN,1957; JOHNSTONE Use

Physical requirements

abrasive (scouring and polishing preparations) acetic acid manufacture acid neutralization

finely pulverized; free of grit

aggregates and road stone agricultural limestone and dolomite alcohol and phenol alkali aluminium oxide (Bayer process) aluminium production ammonia asphalt filler

size varies for each job and for equipment being used; particles 1-3 mm and 1-3 inch in diameter have been used resistant to abrasion; sound; size varies, but coarse (>0.187 inch) to fine (<0.187 inch) is common ground to specification for each job or according to state law stone 1 or 2 to 6 inches in diameter

athletic-field marking barnstone bleaching powder and liquid

size varies according to process; generally 80% should pass through a 200-mesh sieve light in colour stone should pass through an 8-mesh sieve open-textured limestone or chalk preferred

brick glazing

finely ground

Chemical requirements

high-calcium limestone

> 95 % CaC03

free of deleterious substances such as chert, shale, or clay high calcium-carbonate equivalent, at least 80% highcalcium limestone, free of deleterious substances high-salcium limestone with < 1 % silica > 97 % CaC03 and < 1 % silica high-calcium limestone, low in silica

reasonably high purity high-calcium limestone with only traces of . Mn, Fe, MgO, or clay

brick making (silica refractory brick and sand-lime and slag brick bulb growing (in planters) calcium acetate calcium carbide and calcium cyanamide

workable in small chips and of an attractive colour limestone should not decrepitate during burning but should give a tough strong lump

calcium carbonate (precipitated) calcium hydride

cut stone, interior use ashlar, rubble veneering, flagging, and curbing

Fez03 +A1 2 0 3 , trace of S

sm

high-calcium limestone high-purity limestone or dolomite, which gives > 30 % COZ > 97 % total carbonates, < 0.3 % FezO3, <2 % si02, 95 % CaO

ceramics

cut stone, exterior use

> 97 % CaC03, < 0.01 % P, <2 %MgO, maximum of 3 % SiOz, c 0.05 - 0.75 %

111

calcium nitrate carbolic acid and carbonic acid carbon dioxide

chromate and bichromate citric acid coke and gas (gas purification and plant by-products) creameries and dairies dimension stone

impure argillaceous limestone

good weathering resistance; free of deleterious substances good weathering resistance; free from fractures or joints; pleasing aspect free from defects; pleasing appearance; resistant to abrasion if used for flooring or steps good weathering resistance; free from defects, one good face; resistant to abrasion if to be walked on good weathering resistance; one good face; resistant to abrasion if to be walked on

b 0

z

5

B

minimum amount of iron or iron-bearing minerals (pyrite and marcasite) minimum amount of iron or iron-bearing minerals (pyrite and marcasite) minimum amount of iron or iron-bearing minerals (pyrite and marcasite) minimum amount of iron or iron-bearing minerals (pyrite and marcasite) minimum amount of iron or iron-bearing minerals (pyrite and marcasite) w

w

TABLE XXVII (continued) Use monumental stone disinfectants dyes electrical products Epsom salts

00

0

Physical requirements

Chemical requirements

superior weathering resistance; free from defects; uniform; pleasing appearance

minimum amount of iron or iron-bearing minerals (pyrite and marcasite) reasonably high purity high-calcium limestone

stone should all pass a 20-mesh sieve and 97% should pass a 100-mesh sieve stone should pass a 60-mesh sieve

,

explosives fertilizer filler

fill material (other than riprap) filter stone

flux blast furnace open-hearth furnace

foods fungicides and insecticides

usually stone should pass an 8-mesh sieve but be retained on a 20-mesh sieve

dolomite with > 99 % calcium and magnesium carbonates combined pure carbonate rock with as much magnesium as calcium reasonably pure limestone or dolomite

3.5-2.5 or 3.5-1.5 inch sizes are used; rough surface; should withstand 20 cycles of the N a ~ S 0 4soundness test; minimum of fines

minimum amount (if any) of pyrite, marcasite, and clay

size varies from about 0.5-6 inches depending on the user and the economics of the operation; minimum amount of decrepitation is necessary size varies from about 4-1 1 inches depending on the user and the economics of the operation; minimum amount of decrepitation is necessary

vary according to the user and economics of the operation vary with user; generally > 98% CaC03 trace of P cr!

high-calcium limestone, low in Fez03 and AIzo3; composition should be uniform

ga

glass gelatin glue grease leather dressing (tanning)

stone should pass a 16-20-mesh sieve but should be retained on a 100-140 mesh sieve 98 % should pass a 200-mesh sieve and 95 % should pass a 325-mesh sieve

lime

vary with production techniques; stone should be hard and should not decrepitate upon burning; fines are undesirable

lithographic limestone

even texture; free of defects, grit or granular impurities

magnesia recovery from sea water magnesium and magnesium compounds magnesium chloride masonry cement membrane waterproofing mineral feeds for livestock mineral-treatment processes (e.g., flotation) monocalcium phosphate natural cement oil-well drilling

size stone used varies with individual operations

stone should be sound; size varies with operation stone should pass a 200-mesh sieve

finely pulverized

> 98 % total carbonates, < 0.05 % iron

oxide, low in S and P, minimal amount possible of C free of deleterious substances free of deleterious substances high-calcium limestone with < 1.5 % MgO, < I % silica, < 0.5 % Fez03 high-calcium limestone, low in Fe or other metallic impurities; MgO and clay are injurious > 90% CaC03 (preferably 97-98 %) and < 5 % MgC03, < 3 % other impurities for high-calcium lime; > 40% MgC03 and < 3 % other impurities for highmagnesium lime

sm

dolomitic limestone dolomite of high purity 42 % MgC03,55 % CaC03, and Rz03

-=3 % SiOz +

> 95 % CaC03; low (if any) F

high-purity limestone, low in Mg pure, high-calcium limestone limestone or dolomite with 13-35 % clayey material (of which SiOz is 10-22 %) and 4 1 6 % A 1 ~ 0 3 S F e z 0 3 W

m

w

TABLE XXVII (continued) Use

00 h,

Physical requirements

high-calcium limestone

ore concentration and refining (e.g., flotation) paints paper

stone > 3 inches in diameter

petrochemicals (glycol) petroleum refining pharmaceuticals Portland cement

hard impurities are undesirable

poultry grit

stone should pass a @-mesh sieve but should be retained on a 10-mesh sieve

pozzolana cements railroad ballast rayons refractory dolomite and dolomite refractories: raw dolomite calcined dolomite

Chemical requirements

highcalcium limestone, low in Mg, < 2 % AlzOs+Fez03+ acid insoluble material; acid insoluble material should be light in colour and should settle rapidly high-purity limestone (artificially prepared usually) > 75 % CaCO3, < 3 %MgO, < 0.5 % Pz05; for white Portland cement, limestone should be low in Fe ( <0.01% FezO3); low Mn content is desirable high-calcium limestone with < 0.1 % F

various sizes of stone are used; should have a good abrasion hardness and a minimum amount of deleterious substances stone should pass a 0.75-inch sieve; fines are removed; should not disintegrate when heated stone should pass a 0.75-inch sieve; fines are removed; should not disintegrate when heated

>20% MgO,
> 20% MgO, < 0.05% S, < 2 % SiOz

dead-burned dolomite retarder rice milling riprap rock dusting (mines) rock or mineral wool roofing granules sewage and trade-waste treatment silica brick manufacture silicones soap soil and structure stabilization stone chips

stucco studio snow sugar refining (cane and beet) sulfuric acid purification table salt target sheets terazzo

size of stone used varies but is usually <0.5 inch in diameter weather resistant; free from defects that cause spalling and splitting 100% should pass a 20-mesh sieve and 70 % should pass a 200-mesh sieve; should not cake if wetted and dried size of stone used varies with plant operation but 2-5 inches is common

2U % combustible matter; < 5 % free and combined silica

<5

4 5 4 6 % CaC03 or CaC03

3.5-2.5 or 3.5-1.5 inch sizes are used; rough surface should withstand 20 cycles of the Na2S04 soundness test; minimum of fines

high-calcium limestone

free of deleterious substances

high-calcium limestone highcalcium hydrated lime

uniform, attractive colour; hard, durable, and tough; low absorption; free from dust; ability to take a polish; size used varies finely pulverized; light colour size varies with plant operation; stone should retain shape during burning

uniform, attractive colour; hard, durable, and tough; low absorption; free from dust; ability to take a polish; size used varies

+ MgCO3

high-calcium limestone

high purity, >9697% CaC03, < I % SiO2, < 1 4 % MgO, <0.5% iron oxide

w

00

w

TABLE XXVII (continued) Use

w

E Physical requirements

high-calcium limestone with < 3 %MgO, (2 % Fez03 AlzOa, < 2.5 % sioz insoluble residues

textiles tobacco varnish manufacture whiting wire drawing wood pullers wood distillation

Chemical requirements

+

should pass a 200-mesh sieve; no grit; specifications vary with user

+

high-calcium limestone, low in Mg and Fe specifications vary with user

385

PROPERTIES AND USES OF THE CARBONATES

TABLE XXVIII USES IN WHICH AND FOR WHICH WHITING (MANUFACTURED AND ARTIFICIALLY PREPARED) IS USED

(After LAMAR, 1961; supplemented by data from BOWLES and JENSEN, 1947; KEY,1960; and JOHNSTONE and JOHNSTONE,1961) acoustic tile antibiotics asbestos products filler asphalt calcimine and cold water paints caulking compounds ceramic glazes, enamels, and bodies chemical manufacture chewing gum cigarette papers coating on glazed paper confectionery cosmetics crayons disinfectants dolls dressing for white shoes dusting and polishing agents dusting unburned brick to prevent sticking to kiln dusting printing rollers dyes explosives fabric filler facing for molds and cores in brass casting file manufacture fireworks flat wall paint and enamel undercoats flavoring extracts floor coverings food foundry compounds fungicides glue graphite filler grease gypsum plaster insecticides leather goods linoleum linseed oil putty

locomotive works magazine and book papers making buff brick from red-burning clay manufacture of citric acid medicines (pharmaceutical products) metal polish neutralizing in fermentation processes oil cloth oil paints paints paper parting compounds petroleum refining phonograph records picture frame moldings plastics pottery printing ink printing and engraving Putty roofing cement rubber rubber goods (footwear, heels, hard rubber objects, white rubber stock, molded rubber goods, sponge rubber, hose, belts, mats and electric cable insulation) sealing wax ship building shoe manufacturing shoe polishes soap structural iron making toiletries toothpaste (dentifrices) welding electrode coatings white ink whitewash window shades wire insulation

F. R. SIEGEL

TABLE XXIX USES FOR WHICH AND IN WHICH CARBONATE MINERALS (NATUREL AND ARTIFICIALLY PREPARED) ARE USED

(After DANA, 1959; KRAUSet al., 1959; and STECHER, 1960) Mineral

Uses

calcite

As limestone, see Table XXVII; or as whiting, see Table XXVlII; variety Iceland spar used for the Nicol prism in polarizing microscopes to obtain plane polarized light; in tooth powders, white polishes, and whitewash (paint); in removing acidity from wines; as a gastric antacid and for mild diarrhea; ore of calcium.

dolomite

As dolostone, see Table XXVII; ore of metallic magnesium.

magnesite

Dead-burned (MgO with less than 1 % COZ) used in the manufacture of refractory brick linings, furnace hearths, and Sore1 cement; source of magnesia used for the manufacture of many industrial chemicals; mixed with asbestos, serves as a fireproof and heat insulating covering for boilers and steam pipes; calcined magnesite used in flooring, tiling, wainscoting, and sanitary finishes; in tooth and face powders and in polishing compounds; as a filler for rubber; in the manufacture of mineral waters, pigments and paper; used to clarify liquids by filtration; as an antacid and laxative; ore of metallic magnesium.

rhodochrosite

Ore of manganese; used in feeds and as a drier for varnishes; as the pigment “manganese white”; has been used in treating anemia.

siderite

Ore of iron.

smithsonite

Ore of zinc; used polished as a gem or for ornamental purposes; used as a pigment and in the manufacture of porcelain and pottery; has been used topically as a mild antiseptic and astringent in inflammatory skin diseases.

aragonite

No economically important use except as a gem (pearl).

wi therite

Ore of barium; used in the extraction of sugar from sugar beets; as a drilling mud, as an adulterant in white lead, and as a rat poison; in paints, enamels, marble substitutes, and in rubber; used in the ceramics, glass (especially optical glass), vacuum-tube, and paper industries; used for the preparation of many barium compounds.

strontianite

Ore of strontium; used in pyrotechnics and military rockets; in the separation of sugar from molasses; as a lead replacement in certain enamels; in the manufacture of irridescent glass; used in the preparation of many strontium compounds.

cerrussite

Ore of lead; as a pigment in oil paints and water colors; used in certain cements and for making putty and lead-carbonate paper.

malachite

Ore of copper; as jewelry and for ornamental purposes such as vases and veneer for table tops.

azurite

Ore of copper.

trona

Ore of sodium; used in the manufacture of glass, pulp and paper, and in the preparation of sodium compounds; used for water treatment and in the production of nonferrous metals, cleaners, soap, textiles, and dyes.

PROPERTIES AND USES OF THE CARBONATES

387

moving upward. The effect of some technological advances have not been felt yet to any great degree in the United States. Development of the oxygen process for making steel is most encouraging to the carbonate rock and lime producer, because in this process about twelve times more lime is used per day than in the conventional steel production processes. Although European and Japanese steel manufacturers produce large quantities of their steel by the oxygen process (Japan produces about 38 % this way as compared to 10% in the United States), the major steel producers in the United States have been somewhat conservative and slow to convert to this speedy and more efficient technique. Because of domestic and foreign competition and lower prices, however, established companies such as U. S. Steel have been stimulated into constructing oxygen furnaces in an effort to maintain traditional markets and to establish new ones. In other fields, research is leading to new uses for the carbonates. The Texas Crushed Stone Company of Austin, Texas, is experimenting with crushed limestone base in livestock areas on farms in an effort to prevent livestock bogging (KENNERLY, 1963). This company is also interested in other applications on farms and may experiment: ( I ) with limestone floors in poultry houses; (2) with crushed limestone as a base for self-feeding hay to cattle from stacks in pastures; and (3) with its potentially most important use as a base for the hundreds of beef-cattle feeding lots, currently appearing in many of beef-producing states in U.S.A. HEDIN (1963), head of the Chemical Department of the Swedish Cement and Concrete Institute, Stockholm, Sweden, pointed out that lime consumption can be increased if the lime is manufactured for specific uses by selecting starting carbonate rock of known chemical composition and crystal size, and then controlling the burning process. FALKE (1963) described a new method for recovering manganese from manganiferous limestones and slimes, and found that 50-75 % of the total manganese in manganiferous limestones can be recovered as manganese carbonate containing 45 % manganese. Considering that only about 3 % of the manganese used in the United States is of domestic origin this advance is extremely important. Although one may review Tables XXVII-XXIX, trends in production, technological advances or product development, and fully appreciate the importance of carbonate rocks to the development and advancement of our civilization, limestones and dolomites serve other purposes in which they are not actually “used” but for which they are esteemed or have actual economic meaning. For example, caverns and unique speleothem formations that have formed in them (Fig.4) serve as a constant source of education and wonder to those visiting them. In the United States, thousands of visitors each year take guided tours through the Carlsbad Caverns, New Mexico, and the many caves of the Mammoth Cave National Park, Kentucky. The actual dollar ‘value represented by payment for these tours is difficult to assess, but it no doubt exceeds that derived from many of the products listed in the tables of uses (Tables XXVII-XXIX). Similar exhibitions of natural beauty are found in the coral reefs of the Pacific and off the east coast of

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Fig.4. Speleothem formations (stalactites, stalagmites, straws, and flowstone) in the Great Onyx Cave, Mammoth Cave National Park, Kentucky.

the Florida Keys and the Bahamas; and the number of people who visit these features each year represents a good portion of the tourist trade. Unfortunately, in areas where conservation is not practiced or dictated by law, these non-replaceable features (stalactites, stalagmites, or flowstone) or coral specimens are sold at local souvenir stands for ornamental purposes. In several areas where underground quarries have been worked out or where caves are present, the land owner can make substantial profit by renting the empty space for storage. Because of the low (and constant) temperature and humidity of these underground facilities, they are ideal for raising mushrooms, and for the storage of records, frozen foods, medicinals, bonded whiskey, military equipment, and other products. The U. S. Government has set up specificationsfor theseunderground areas, which if they are followed,can lead to the eventual rental of the storage facilities to the government at favorable fees. STEARN(1963) has summarized these for mined-out limestone caves (or quarries) to be used as storage areas of high security and unrivalled material preservation: (I) the minimum size should be at least 200,000 sq. ft. and there should be a geometrical pillar arrangement, spaced at least 30 ft. apart, and a minimum ceiling height of 14 ft.; (2) only drifttype entryways are allowed and the exits and entrances must be serviced by paved roadways; (3) proximity to a railroad spur is desirable; (4) there must be at least

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50 ft. of overburden; ( 5 ) a 4-h fire rating is necessary for the installed doors and reinforced concrete walls separating the different areas, and there should be a complete automatic sprinkler system throughout the facility; and (6) proper equipment for temperature maintenance (between 55 and 70 O F ) and for relative humidity maintenance (30-50 %) must be installed. It is most probable that in the future, such rigidly constructed underground areas will house power plants or nuclear reactors. The magnitude of the importance of carbonate rock to man can be further emphasized by the previously cited fact that more than one-half of the known petroleum and natural gas reserves are in carbonates, as well as a great percentage of our past and existing metalliferous reserves. Also, that precious commodity water comes from limestone aquifers in many parts of the world, and porous and permeable carbonate rock units have been developed for storage of natural gas and liquefied petroleum products. On adding to this the secrets of the earth’s history that have been, are being, and will be revealed by detailed, systematic studies of the carbonate rocks and their fossils and other than carbonate mineral content, one may see that “use” although considered mainly from an economic aspect, can be extended to include academic studies which can and many times do lead to economic development and successful exploitation.

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REFERENCES INDEX

ABELSON, P. H., 9, 72, 102, 136 ABELSON, P. H. and HOERING, T. C., 199, 206 ADAMS, E. and NICHOLSON, J., 212, 220 ADAMS, J. E. and RHODES, M. L., 136 ADAMS,L. H., 178, 189 ADLER,H. H., 373, 389 ADLER,H. H. and KERR,P. F., 372, 374, 375, 389 ALDERMAN, A. R.,27, 136 ALDERMAN, A. R. and SKINNER, H. C. W., 55, 136, 177, 183, 186, 189 ALDERMAN, A. R. and VONDER BORCH,C. C., 87, 116, 117, 136, 177, 189 ALEKIN, 0. A., 3, 20 ALEXANDER, L. E. and KLUG,P. H., 325, 330 ANGINO,E. E., 9, 327, 330, 372, 389 ANGINO,E. E. and GR ~ GL EN., R , 372,389 ANGINO,E. E. and SIEGEL, F. R.,325, 330 ANGINO,E. E., ARMTAGE, K. B. and TASH,J. C., 86, 136 ANONYMOUS, 346, 347, 378, 389 ARABIAN-AMERICAN OIL Co. STAFF,235, 236, 249 ARPER,W. B., 136 ARRHENIUS, G., KJELLBERG, G. and LIBBY, W. F., 330 A. S. T. M., 351, 352, 353, 389 ATCHISON, T. C., DUVALL, W. I. and PETKOF, B., 363, 389 ATWATER, G. I., 2, 20 AUDLEY-CHARLES, M. G., 136 AZAROFF, L. V. and BUERGER, M. J., 324, 331

K. G., 136 BARGHOORN, E. S., MEINSHEIN, W. G. and SCHOPF, J: W., 136 BARLETT, H. H., 230 BARNES, I., 137 BARNES, I. and BLACK,W., 179, 182, 190 BARNES, J. W., LANG,E. J. and POTRATZ, H. A.. 84, 137 BARNES, V. E., 326, 330, 365, 390 BARON,G. and FAVRE,J., 5,20 BARON,G., CAILL~RE, S., LAGRANGE, R. and TH., 320, 321, 330 POBEGUIN, BARTH,T., 213, 220 BASS,N. W., 242, 249 BATHURST, R. G. C., 151, 166,211, 220 BAXTER, J. W., 137 BAYLISS, P., 316, 330 BAYLISS,P. and WARNE,S., 316,330 BEALES, F. W., 273, 330 BECK,C. W., 316, 318, 322, 330 BELL,K. G., 29, 91, 137 BELL,P. M., ENGLAND, J. L. and SIMMONS, M. G., 137 BENDORAITIS, J. G., BROWN,B. L. and HEPNER, L. S., 227, 249 BERG,L. G., 330 BERGER, R.,HORNEY, A. G. and LIBBY,W. F., 328, 330 BERGER, W., 72, 137 BERGMANN, W., 228, 249 BERGSTROM, R. E., 326, 330, 372, 390 BERNER, R. A., 137 BERRY,L. G. and MASON,B., 279,330 BAAS-BECKING, A. V. and GALLIHER, G., 136 BEVELANDER, G., 329,330 BAERTSCHI, P., 195,197,198,200,204,206 BIRCH,F., SCHAIRER, J. F. and SPICER,H. C., BAEKTSCHI, P. and SILVERMAN, S. R.,199, 206 351, 354, 355, 356, 357, 358, 359, 360, 390 BAKER, D. R., 241, 242, 249 BISQUE,R. E., 330 BAKER, E. G., 233, 249 BISQUE,R. E. and LEMISH, J., 278,297,304,330 BAKER, N. E. and HANSON, F. R. S., 236, 249 BISSELL,H. J., 272, 273, 274, 330 BALL,S. M. and BECK,A. W., 365, 390 BISSELL, H. J. and CkILINGAR, G. V., 104, 137 BALLIE,A. D., 235, 249 BITTERLI, P., 137, 235, 249 BANKS,J. E., 288, 330 BLAIR,B. E., 351, 390 BANNER, F. T. and WOOD,G. V., 102, 136 BLACK,W., 181, 189 BAR, O., 184, 185, 190 BLACK,W. A. P. and MITCHELL, R.L., 53, 137 BARANOV, V. I., RONOV, A. B. and KUNASHOVA, BLACKMON, P. D. and TODD,R., 49,60,75,137

396 BLOSS,F. D., 280, 330 BLUMER, M. and OMAN,G. S., 228,249 BLUMER, M. and THOMAS, D. W., 228, 249 BLUMER, M., MULLIN,M. M. and THOMAS, D. W., 228,249 BODINE JR., M. W. and HOLLAND, H. D., 370, 390 BODUNOV-SKVORIXOV, E. I., 237, 249 BOUMA, A. H., 288, 330 BOWEN,H. J. M., 65, 137, 199, 206 BOWEN,N., 217, 220 BOWENJR., 0. E., 378, 390 BOWEN,R., 199, 206 BOWLES, O., 373, 378, 390 BOWLS, 0. and JENSEN,N. C., 373, 378, 385, 390 BRADLEY, D. E., 286, 287, 330 BRADLEY, W. F., BURST,J. F. and GRAF,D. L., 137, 330 BRAY,E. E. and EVANS,E. D., 243, 249 BRENDA, B. J. and BRUNFELT, A. O., 137 BRILL,O., 318, 331 BRINDLEY, G. W., 324, 331 BROD,I. O., 237, 249 BROECKER, W. S., 49, 84, 137, 328, 331 BROECKER, W. S. and ORR,P. C., 74, 137,231 BROOKS, D. B., 137 BROOKS, J. E. and CLARK,D. L., 372, 390 BROOKS, R. R. and RUMBSBY, M. G., 137 BROVKOV, G. N., 87, 106, 128, 129, 130, 137 BROWN,G., 324, 331 BROWN,W. W., 211,220 BUEHLER, E. J., 273; 331 BURGER, D., 282, 331 BURNHAM, G., 217, 220 CAILL~RE, S., 317, 323, 331 CAILL~RE, S. and POBEGWIN, TH., 323, 331 CALLEGARI, E., 217,220 CALVERT, S. E. and VEEVERS, J. J., 289, 331 CAMPBELL, F. A. and LERBEKMO, J. F., 137 CAPDECOMME, L. and P m u , R., 323, 331 CAROZZI, A. V., 151, 166, 286, 331 CARROLL, J. J. and GREENFIELD, L. J., 61, 74, 137 GANG, L. L., 137, 371, 390 GAVE, K. E., 8, 26, 55, 59, 60, 61, 77, 78, 79, 83,84,103, 134,137,181, 186,190,325,331, 366,390 CHAVE,K. E., DEFFEYES, K. S., WEYL,P. K., GARRELS, R. M. and THOMPSON, M. E., 138, 390 CHAYKOVSKAYA, E. V., 234, 249 CHENG, K. L., KURTZ,T. and BRAY,R. H., 299, 308, 331 CHIBNALL, A. C. and PIPER,S. H., 227,243,249

REFERENCES INDEX

CHILINGAR, G. V., 1, 5, 6, 10, 12, 20, 59, 77, 78, 102, 103, 105, 110, 113, 134, 135, 138, 153, 166 CHILINGAR, G. V. and BISSELL, H. J., 20, 85, 99, 138, 153, 166 CHILINGAR, G. V. and TERRY, R. D., 110, 138, 305, 331 CHILINGAR, G. V., BISSELL, H. J. and WOLF, K. H., 28, 89, 99, 138, 255, 287, 331 CLARKE, F. W., 361, 364, 365, 390 CLAYTON, R. N., 195, 198, 200, 204, 205, 206, 331 CLAYTON, R. N. and DEGENS, E. T., 111, 138, 195, 197, 200, 206, 329, 331 CLAYTON, R. N. and EPSTEIN, S., 15, 193, 199, 200, 202, 203, 204, 205, 206, 328, 329, 331 CLOUDJR., P. E., 74, 95, 115, 138, 151, 166 CLOWES, F. and COLEMAN, J. B., 296, 331 COLBY,S. F., 373, 378, 390 COMPSTON, W., 194,195,199,202,206,329,331 COMSTOCK, H. B., 376, 390 CORDIER, P., 220, 222 CORLESS, J. T., 206 CORLESS,J. T., RAHN,K. A., and WINCHESTER, J. W., 206 CRAIG,H.,14,193,194,195,196,197,198,206, 328, 329, 331 CRICKMAY, G. W., 20 CROW,S. C., 360, 390 CURL,R. L., 138 CUTHBERT, F. L. and ROWLAND, R. A., 320, 331 CUVILLIER, J., 287, 288, 331 D’ALBISSIN, M., 214, 215, 216, 220 D’ALBISSIN, M. and DE RANGO,C., 286, 332 DALBISSIN,M. and ROBERT,M., 214, 220 DALEISSIN,M., FORNACA-RINALDI, G. and TONGIORGT, E., 220, 372, 390 M., SAPLEVITCH, A. and SAUCIER, DALEISSIN, H., 214, 220 DANA,J. D., 349, 386, 390 DANIELS, F., 326, 332 DANIELS, F., BOYD,C. A. and SAUNDERS, D. F.. 326. 332, 371, 390 DANIELSON, A., 217, 220 DANSGAARD, W., 199, 200,207 DAUGHTRY, A. C., PERRY,D. and WILLIAMS, M., 15, 206, 207, 328, 329, 332 DAVIES,T. T. and HOOPER,P. R., 325, 332 DEAN,J. A., 310, 332 DEBENEDETIT, A., 215, 220 DEBOO,P. B., 152, 160 DEER,W. A., HOWIE,R. A. and ZUSSMAN, J., 8, 27, 138, 279, 281, 332, 349, 350, 352, 390 DEFFEYES, K. S. and MARTIN,E. L., 332

REFERENCES INDEX

397

ERENBURG, B. G., 152, 166 DEFFEYES, K. S., LUCIA,F. J. and WEYL,P. K., ERICSON, D. B. and WOLLIN,G., 333 177, 190 B. D., 259, 261, 262,271, 333 DEGENS,E.T., 111,114,116,138,240,241,329, EVAMY, EVANS,R. C., 139 332 DEGENS, E. T. and EPSTEIN, S., 15, 194, 195, EVANS,W. D., 58, 71, 139 198, 200, 201, 202, 203, 204, 207, 279, 329, FAIRBANKS, E. E., 260, 333 332 R. W., 9, 11, 12, 20, 99, 133, 134, DEGENS, E. T., HUNT,J. M., REUTER, J. H. and FAIRBRIDGE, 139, 287,288, 327, 333 REED,W. E., 138 DEGENS, E. T., PIERCE, W. D. and CHILINGAR, FALKE,W. L., 387, 390 FANALE, E. P. and SCHAEFFER, 0. A., 328, 333 G. V., 90, 138 DEGENS, E. T., WILLIAMS, E. G. and KEITH, FAUST,G. T., 318, 321, 323, 333 FEIGL, F., 263, 267, 268, 269, 289, 333 M. L., 28, 138, 332 FLASCKA, H., 300, 333 DE VRIES,H., 332 FLUGEL, E. and FLUGEL-KAHLER, E., 111, 112, DIAMOND, J. J., 310, 332 114, 139, 289, 329, 333 DIEBOLD, F. E., LEMISH, J. and HILTROP, C. L., FOLK,R. L., 100, 114, 139, 289, 333 325, 332 DODD,J. R., 76, 77, 79, 81, 139 FOLK,R. L. and ROBLES,R., 289, 333 FOLK,R. L., HAYES, M. 0. and SHOJI,R., 289, DOLGOV, G. I., 6, 20 333 DUNBAR, C. 0. and RODGERS, J., 96, 139 FORSMA J.~P., and HUNT,J. M., 238,239,249 DUNNINGTON, H. V., 236, 249 FRETTER, V., 139 DUNTON, M. L. and HUNT,J. M., 228, 249 FRIEDEL,J., 215, 220 DURELLI, A. J. and FENER, L., 360, 390 DURHAM, J. W., 152, 166 FRIEDMAN, G. M., 139,259,260,262,264,265, 267, 268, 270,272, 282, 333 DUVALL, W. I. and ATCHISON, T. C., 362, 390 FROST,A. V., 231, 249 EASTON, A. J., 294, 303, 332 FUCHTBAUER, H., 139 EASTON, A. J. and GREENLAND, L., 302, 332 FUCHTBAUER, H. and GOLDSCHMIDT, H., 87, 100, 139 EASTON, A. J. and LOVERING, J. F., 305, 310, FUKAI,R. and MEINKE, W. W., 49, 53, 139 332 EASTON, W. H., 332 FYFE,W.S., 104, 139 ECKEL,E. C., 365, 390 FYFE, W. S. and BISCHOFF, J. L., 139 ECKELMANN, W. R., 198 ECKELMANN, W. R., BROECKER, W. s., WHIT- GABINET, M. P., 321, 333 LOCK,D. W. and ALLSUP,J. R., 194,207 GALLE,0. K., 361, 364, 390 ELLENBERGER, F., 217, 220 GALLE,0. K. and RUNNELS, R. T., 361, 390 ELLING~OE, J. and WILSON,J., 332 GAMKOSIAN, A., JANSSON, A. C. and UMLANDT, EL WAKEEL, S. K. and RILEY,J. P., 139 R. M., 365, 373, 390 EMERY, K. O., 327, 332 GARLICK, G. D., 195, 198, 200, 204, 207 EMERY, K. 0. and BRAY,E. E., 327, 332 GARLTCK, W.G., 85, 140 EMERY,K. 0. and HOGOAN,D., 228, 249 GARN,P.D., 323, 333 EMILIANI,C., 70, 139, 199, 200, 207, 329, 332 GARN,P. D. and KESSLER, J. E., 323, 333 EMILIANI, C. and EDWARDS, G., 332 GARRELS, R. M., 86, 104, 140 ENGEL,A. E. J. and ENGEL,C. 139 GARRELS, R. M. and DREYER, R. M., 104,140, ENGEL,A. E. J., CLAYTON, R. N. and EPSTEIN, GARRELS, R. M.,DREYER, R. M. and HOWLAND S., 15, 198,200, 202,204,205,207, 329, 332 A. L., 140 EPSTEIN,S., 15. 193, 207, 333 GARRELS, R. M., THOMPSON, M. E. and SIEVER, EPSTEIN, S. and MAYEDA, T., 199, 200, 207 R., 140, 172, 173, 174, 175, 178, 179, 190, EPSTEIN,S.,BUCHSBAUM, R., LOWENSTAM, H. A. 368, 391 and UREY,H. C., 193, 199, 204, 205, 207, GAULT,H. R. and WELLER, K. A., 333 329, 333 GEDROIZ, K., 278, 333 EPSTEIN, S., GRAF,D. L. and DEGENS, E. T., GEHMAN JR., H. M., 71,140,231,234,240,250 199, 201, 202, 203,207, 333 GERARDE, H. W. and GERARDE, D. F., 227,249 ERDMAN, J. G., M A R L EE. ~ ,M. and HANSON, GERMAN, K., 140 W. E., 228, 249 GIBBS,J. W., 170, 171, 172, 177, 178, 190 EREMENKO, N. A., 20,21 GILBERT, C. M. and TURNER, F. J., 283, 333

398

REFERENCES INDEX

GILLISON, J. L., 351, 366, 373, 391 GRWER,R. M., 318, 320, 334 GINSBURG, R. N., 234,249 GULBRANDSEN, R. A., 365, 391 GLAGOLEVA, M. A., 72, 140 GULYAEVA, L. A.gnd ITKINA, E. S., 28,29,141 GLOVER, E. D., 333 GODWIN,F. R. S., 328, 333 HAAS,C., 214,221 GOGUEL, J., 210, 216, 221 HAGN,H., 288, 334 GOLDBERG, E. D., 52, 72, 73, 88, 91, 105, 140 HAGUI,R. D. and SAADALLAH, A. A., 141 GOLDBERG, E. D. and ARRHENIUS, G. 0. S., HALLA, F., CHILINGAR, G. V. and BISSELL,H. J., 104,140 175, 178, 184, 185, 190 GOLDICH, S. S., INGAMELLS, C. 0. and THAEM- HAMBLIN, W. K., 289, 330 LITZ, D., 365, 391 HANDIN, J. and HAGAR,R., 210, 221 GOLDMAN, M, 140 HANDIN, J., HIGGS,D., LEWIS,D. and WEYL, GOLDSCHMIDT, V. M., 29, 105, 140 P., 215, 221, 327, 334, 372, 391 GOLDSCHMIDT, V. M., KREJCI-GRAF, K. and HANZAWA, S., 288, 334 WITTE,H., 29, 140 HARBAUGH, J. W., 151, 166, 273, 334 GOLDSMITH, J. R., 26, 140, 370, 391 HARBAUGH, J. W. and DEMIRMEN, F., 289, 334 GOLDSMITH, J. R. and GRAF, D. L., 366, HARBAKEN, L. and GREDAY, T., 212, 221 370, 391 HARDER, H., 89, 97, 141 GOLDSMITH, J. R. and HEARD, H. C.,391 HARKER, A., 221 GOLDSMITH, J. R. and NORTHROP, D. A., HARKER, R. I., 141 370, 391 HARKER, R. I. and TUTTLE,0.F.,26,141,217, GOLDSMITH, J. R., GRAF,D. L. and HEARD, 221, 325, 334, 366, 391 H. C.,391 HARRIS,R. C., 141 GOLDSMITH, J. R., GRAF,D. L. and JOENSUU, HARVEY, R. D., 391 0. I., 26, 140, 325, 333 HAUL,R. A. W. and HEYSTEK, H., 318, 335 GOLDSMITH, J. R., GRAF,D. L., WITTERS, J. HAUN,J. D. and LEROY,L. W., 335 D. A., 26,140,325,334,391 and NORTHROP, HAY,W. W. and TOWE,K. M., 286, 335 GOREAU, T. F., 71, 140 HAYES, J. R., 335 GOREAU, T. F. and GOREAU, N. I., 75,140 HEDBERG, H. D., 248, 250 GORLITSKIY, B. A. and KALYAEV, G. I., 130,140 HEDBERG, R. M., 259, 261, 275, 335 GORSKAYA, A. I., 230, 231, 250 HEDGPETH, J. W., 141 GOTO,M., 4, 27, 86, 93, 94, 95, 140, 259, 325, HEDIN,R., 387, 391 334 HEEGER, J. E., 259, 270, 335 GRAF,D. L., 23,27,28,29,49, 50,62, 72, 104, HEEZEN, B. C. and JOHNSON 111, G. L., 272,274, 140, 324, 334, 352, 361, 391 335 GRAF,D. L. and GOLDSMITH, J. R., 13, 152, HEIDE,F. and CHRIST,W., 141 166, 176, 190, 324, 325, 334, 366, 391 HENBEST, L. G., 259, 261, 267, 335 GRAF,D. L. and LAMAR, J. E., 141,366,370, HERZOO, L. F., ALDRICH, L. T., HOLYK, W. K., 391 WHITING, F. B. and AHRENS, L. H., 328, 335 A. J. and SHIMP,N. F., HIGGS,D., FRIEDMAN, GRAF,D. L., EARDLEY, M. and GEBHART, J., 214, 221 177, 190 GRASENICK, F. and GEYMEYER, W., 259, 334 HILTROP,C. L. and LEMISH, J., 325, 335 HIRST,D. M., 69, 141 GRAYSON, J. F., 141, 334 HIRST,D. M. and NICHOLLS, G. D., 279, 335 GREENFIELD, L. J., 55, 141 HIRT,B. and EPSTEIN, S., 205, 206, 207 GR~GOIRE, C.,286, 334 HOBSON, G. D., 233, 250 GR~GOIRE, C.and MONTY,C., 286, 334 H. D., BODTNE, M. W., BORCSIK, M., GRIGGS, D., TURNER, F. and HEARD, H. C., 21 3, HOLLAND, 22 1 COLLINS,P., KIRSIPU,T. V., ROSENBERG, GRIM,R. E., 276, 278, 334 P. E., SAWKINS, F. J. and TSUSUE, A., 26,88, GRIMSHAW, R. W.,HEATON, E. and ROBERTS, 141 HOLLAND, H. D., BORCSIK, M. and GOLDMAN, A. L..323. 334 E., 141 GROSS,M. G., 141, 329. 334 HOLLAND, H. D., KIRSIPU,T. V., HUEBNER, GROVES. A. W. 305, 306, 334 J. S. and OXBOUGH, GRUBENMAN, U., 218, 221, 222 V. M., 179,181,190,391 HOLLMANN, R., 234,250 GRUNAU,H. R., 286,288, 334 HOLMES, A., 221, 222 GRUS, H., 282, 334

REFERENCES I N D E X

399

S. M., 142 KAYCHENKOV, M. M. and KAZAKOV, A. V., TIKHOMIROVA, V. I., 172, 173, 114, 176, 190 PLOTNIKOVA, KEELING,C. D., 194,207 KEITH,M. L., 336 G. M., 195,197, KEITH,M. L. and ANDERSON, 201, 328, 329, 336 E. T., 142,336 KEITH,M. L. and DEGENS, KEITH,M. L., ANDERSON, G. M. and EICHLER, R., 336 KELLER, W. D., SPOTTS, J. H. and BIGGS,D. L., 372, 392 KENNEDY, G. C., 281, 286, 336 KENNERLY, A. B., 387, 392 KESSLER, D. W. and SLIGH,W. H., 351, 363, 392 KEY,W. W., 385, 392 Y. and LOUIS,M., 244, 250 KHALIFEH, KING,R. J., 142 KINSMAN, D. J. J., 142 KISSINGER, H. E., MCMURDE, H. F. and S ~ P ILLING, L. V., 152, 166 ILLING, L. V., WELLS,A. I. and TAYLOR, sow, B. S., 316, 317, 323, 336 Y., 58, 95, 96, 142 KITANO, J. C. M., 141 KITANO,Y. and HOOD,W. H., 158, 166 IMBRIE, J., 141, 289, 335 KITSON,R. R. and MELLON, M. G., 303, 336 E. G., 289, 335 IMBRIE, J. and PURDY, KITEL, C., 371, 392 IMBT, W. C., 348, 392 KLOTZ,M., 178, 190 E., 57,72,74,95,116,141,326,335, INGERSON, KNEBEL, G. M. and RODRIQUEZ-ERASO, G., 366, 392 226, 250 IRELAND, H. A., 257, 335 V. and NEMECZ, E., 321, 323, 336 ISENBERG, H. D., LAVINE, L. S., WEISFELLNER,KOBLENCZ, K o c ~ zF. , F. and TITZE,H., 142 H. and SPOTNIZ,A., 141 KONISHI,K., 49, 142 Ims JR., W., 257, 335 KRACEK,F. C., 367, 392 KRAMER, J. R., 142, 178, 179, 190 JAMIESON, J. C., 142, 158, 166, 217, 221 b u s , E. H., HUNT,W. F. and RAMSDELL, J. R., 142 JAMIESON, J. C. and GOLDSMITH, JEFFERY, P. M., COMPSTON, W., GREENHALGH, L. S., 349, 386, 392 K. B., 29, 50, 86, 100, 104, 122, D. and DE LAETER, J., 195, 207, 328, 329, KRAUSKOPF, 142 335 KREJCI-GRAF,K., 230,250 JODREY, L. H., 142, 329, 335 KREJCI-GRAF, K. and WICKMAN, F. E., 194,207 N. M., 255, 272, 326, 335 JOHNSON, KRINSLEY, J. H., 335 D., 101, 107, 108, 109, 142 JOHNSTON, J., MERWIN,H. E. and WILLIAMSON,KRINSLEY, D. and BIERI,R., 49, 142 JOHNSTON, E. D., 96, 142 KRUGER, P., 142, 143 S. J. and JOHNSTONE, M. G., 360, KUBLER,B.,82, 87, 114, 115, 116, 143, 336 JOHNSTONE, 364, 373, 378, 385, 392 KUDYMOV, B. Y.,85, 122, 128, 143, 289, 336 KULP,J. L., 316, 328,336 JONES, B. F., 177, 183, 190 KULP,J. L., KENT,P. and KERR,P. F., 322,336 JUNG,J., 221, 222 E., 250 JURG,J. W. and EISMA, KULP,J. L., TUREKIAN, K. K. and BOYD,D. W., JURIK,P., 336 62, 64, 65, 66, 69, 70, 78, 79, 80, 102, 108, 115, 143, 328, 336 KAHLE,C. F., 142 KULP,J. L., WRIGHT,H. D. and HOLMES,R. J., KALLE,K., 53, 142 322, 336 KAMB,W., 213, 221 S. I., 74, 143 KUZNETSOV, KANSAS BUILDINGSTONE ASSOCIATION, 352, S. I., IVANOV, M. V. and LYALIKUZNETSOV, 392 KOVA, N. M., 6, 20, 143 K. A., 143 KAUFFMAN, A. J. and DILLING,E. E., 320,336 KVENVOLDEN, HONJO,S., FISCHER, A. G. and GARRISON, R., 141 HOOD,D. W., 72, 141 HOOD,D. W., PARK,K. and SMITH,J. B., 141 HOOPER, K., 49, 141, 325, 335 HOWELL, J. E. and DAWSON, K. R., 283, 335 F. M., 325, HOWIE,R. A. and BROADHURST, 335 Hsu, K. J., 141, 179, 181, 182, 183, 185, 190, 327, 335, 392 HUANG, C. K. and KERR,P. F., 312, 374, 375, 392 HUEGL,TH., 335 P. W., BRADLEY, W. F. and GLASS, HUGHES, H. D., 325, 335 HUNT,J. M., 229,230,231, 235,239, 240,250 HUNT,J. M. and JAMIESON, G. W., 226, 250 279, 335 G. E., 54, 141 HUTCHINSON,

400 LADD, H. S., 143 LAFFITE, P., 212, 217, 221 LALOU,C., 74, 143 LAMAR,J. E., 257,258, 273, 336, 365, 373,376, 378,385, 392 LAMAR,J. E. and SHRODE,R. S., 27, 143 LAMAR,J. E. and THOMPSON, K.B., 25,143,336 LANDERGREN, S., 194,207 LANDERGREN, S. and MANHEIM, F. T., 81, 90, 143 LANE,D. W., 273, 336 LANE,N. G., 336 LANGE,N. A., 349,377, 392 LANGMUIR, D., 143, 189, 190 LARSEN,E. S. and BERMAN, H., 350, 392 LARSEN,G. and CHILINGAR, G. V., 20 LEAVASTU, T. and THOMPSON, T. G., 53, 143 LEE,P. J., 275, 336 LEES, A., 336 LEHNINGER, A. L., 73, 143 LEITMEIER, H. and FEIGL, F., 259,263,265,336 LEMBERG, J., 260, 262, 263, 336 LEMISH,J., 278, 341 LE RIcm, H. H., 143 LERMAN, A., 143 LEUTWEIN, F., 81, 143 LEWIS,D. R., 326, 336, 372, 392 LEWIS,D. R., WEYL,P. K., HANDIN, J. W. and HIGGS. D. V., 336 LEWIS,G. N. and RANDALL, M., 178, 190 LIBBY, w. F., 327, 328, 337 LILEY,P. E., TOULOUKIAN, V. S. and GAMBILL, W. R., 368, 392 LWNS, R. C., BERGY, E. G. and POSNER, A. S., 69,75, 143 LINDBLOOM, G. P. and LUPTON, M. D., 229,250 LIPPMANN,N. F., 318, 337 LLOYD,R. M., 276, 329, 337 LOGVINENKO, N. V. and KOSMACHEV, V. G., 27, 106, 143 LOGVINENKO, N. V., KARPOVA,G. V. and KOSMACHEV, V. G., 286, 337 LONG,G., NEGLIA,S. and FAVRETTO, L., 71, 143 LONGINELLI, A. and TONGIORGI, E., 329, 337 LOUGWN,G. F., 365, 392 MUPEKINE, I. S., 280, 337 Low, J. W., 337 LOWENSTAM, H. A., 55, 56, 57, 58, 60, 66, 75, 76, 78, 79, 81, 100, 105, 109, 114, 143, 153, 166, 329, 337 LOWENSTAM, H. A. and EPSTEIN,A., 14, 198, 199,200, 202, 207, 329, 337 LUCAS,G., 221, 222 LUCIA,F. J., WEYL,P. K. and DEFFEYES,K. S., 152, 166

REFERENCES INDEX

MACDIMID, R. A., 326,337,372,392 MACDONALD, G., 213, 221 MACDONALD, G. J. F., 158, 166, 177, 190 MACHATSCHKI, F., 144 MACKENZIE, R. C., 323, 337 MAGDEFRAU, F., 144 MALAN,S. P., 85, 91, 144 MAWUGA, D. P., 53, 144 MAIR,B. J. and MARTINEZ-PICO, J. L., 227,250 MAMET, B., 210, 221, 222 MANHEIM, F. T., 144 MANN,V. I., 266, 337 MANSON, V. and IMBRIE,J., 337 MARINOS,G. and PETRASCHEK, W., 217, 221 MASON,B., 52, 54, 105, 144 MAXWELL, W. G. H., JELL,J. S. and MCKELLAR, R. G., 83, 84, 113, 144, 337 MCAULIFFE, C., 233, 250 MCCREA,J. M., 199, 207, 279, 337 MCCRONE, A. W., 272, 273, 337 MCIVER,R. D., 279, 337 MCKELVEY, V. E., SWANSON, R. W. and SHELDON, R. P., 365. 392 MEDLIN,W. L., 97, 144 MEINSCHEIN, W. G., 228, 250 MENNING, J. J. and VITTIMBERGA, P., 288, 337 MEYER,R. and TAYLOR, D. W., 337 MICHEL,R., 221 MIGDISOV, A. A., 127, 144 MILLER,J. B., EDWARDS, K. L., WOLCOTT, P. P., ANISGARD, H. W., MARTIN,R. and H., 236, 250 ANDEREGG, MOORE,L. E., 326, 337 MONAGHAN, P. H. and LYTLE,M. L., 96, 97, 144 MOORHOUSE, W. W., 279, 337, 350, 392 MULLER,G., 337 MULLER,W., 144 MUNNICH,K. O., 197, 207 MUNNICH,K. 0. and VOGEL,J. C., 194, 195, 196, 207, 337 MURRAY,J. A., FISHER,H. C. and SHADE, R. W., 321, 337 MURRAY, J. W., 92, 96, 144 MURRAY, R. C., 151, 166 Muzn, E. 0. and SKINNER, H. C. W., 144 NAGY,B., 9, 20 NATIONAL BUREAUof STANDARDS, 314, 337, 364, 365, 392 NAYUDU, Y. R., 337 NEHER,J. and ROHRER, E., 74, 144 NERUCHEV, S. G., 242, 245, 246, 250 NEWELL,N. D. and RIGBY,J. K., 61, 144 NICHOLLS,G. D. O., CIIRL,H. and BOWEN, V. T., 53, 144

REFERENCES INDEX

40 1

RAY,S., GAULT,H. R. and DODD,C. G., 276, 277, 278, 338 R., 23, 62, 145, REVELLE, R. and FAIRBRIDGE, 338 REY,M. and NOUET,G., 288, 338 T.S., SHRIVER, D. S., FALL,H. H., OAKWOOD, REYNOLDS, R. C., 145 MCALEER, W. J. and WLJNZ,P. R., 227,250 W. I., RICE,T. R., 145 OBERT,L., WINDES,S. L. and DUVALL, RIEKE111, H. H., CHILINGAR, G. V. and Ro351, 392 BERTSON JR., J. o., 2, 20 OBORN,E. T., 144 RIEKE,J. K., 326, 338 OCKERMAN, J. B. and DANIELS,F., 326, 338 H. P., 289, 305,338 ODUM,H. T., 62, 64, 66, 67, 68, 78, 81, 82, 87, RILEY,J. P. and WILLIAMS, RIOULT,M. and RIBY,R., 289, 338 88, 89, 101, 102, 108, 109, 113, 114, 144 R. N., 204,205, RITCHIE,A. S., 104, 145, 279, 341 O’NEILL,J. R. and CLAYTON, RIVIERE,A., 176, 190 207 RIVI~RE, A. and VERNHET, S., 145 OPPENHEIMER, C. H., 72, 74, 144 G. R., MCGRATH, I. M., 176, ROACH,C. H., JOHNSON, OPPENHEIMER, C. H. and MASTER, J. G. and SPENCE, F. H., 393 187, 190 ROBBINS, C. R. and KELLER,W. E., 276, 338 ORME,G. and BROWN,W., 211, 221 J., 260, 264, 338 ~ S T L U N D ,H. G., BOWMAN, A. L. and RUSNAK, RODGERS, RONCA,L. B., 312, 393 G. A., 327, 338 A. B., 10, 11, 20, 134, 135, 145, 238, RONOV~ OSTROM, M. E., 50, 90, 144, 277, 338 250 .. OWEN,E. W. 235,250 A. I., 118, 120, OXBURGH, V. M., SEGNIT, R. E. and HOLLAND, RONOV,A. B. and ERMISHKINA, 121, 122, 123, 124, 145, H. D., 88, 144 RONOV,A. B. and KORZINA, G. A., 24, 125, 126, 133, 145 PANTIN,H. M., 144 ROSENBERG, P. E., 26, 145, 325, 338, 370, 393 PAPILHAU, J., 317, 323, 338 ROSENBERG, P. E. and HOLLAND, H. D., 180, PARKSJR., J. M., 326, 338, 372, 392 181, 187, 190, 370, 393 J. and REEDER, W., 306, 338 PATTON, Ross, C. A., 265, 338 PEARN,W. C., 372, 393 S. F., GLOVER,E. D. and GIBSON, Ross, C. A. and OANA,S., 329, 338 PERCIVAL, ROSTOKER, D. and CORNISH, R., 338 L. B., 258, 338 R. A. and JONES, E. C., 317,338 PERRY,R. H., CHILTON,C. H. and KIRK- ROWLAND, ROWLAND, R. A. and LEWIS,D. R., 318, 339 PATRICK, J. D., 367, 393 RUBEY, W. W., 134, 145 PETERSON, M. N. A., 278, 338 PETERSON, M. N. A., BIEN,G. S. and BERNER, RUBIN,M., LIKINS,R. C. and BERRY,E. G., 328, 339 R. A., 144 RUCKER, J. and VALENTINE, J. W., 81, 92, 145 PFLUG,H. D., 145 G., 145 A., 217, 221 RUDDIGER, PHEMISTER, J. and MACGREGOR, RUKHIN,L. B., 3, 20 PHILPPI,G. T., 226, 239, 243, 250 RUNNELS, R. T. and DUBINS,I. M., 145 PILKEY,0. H., 103, 145 J. A., 50,145 RUNNELS, R. T. and SCHLEICHER, PILKEY,0. H. and GOODELL, H. G., 49,79,80, A. P., 339 RUOTSALA, 82, 108, 115 R. J., 152, 166 PILKEY,0. H. and HOWER,J., 49, 77, 78, 79, RUSSELL, 80, 145 F. F., 259, 339 SABINS, PITRAT,C. W., 326, 338, 393 SACAL,V., 288, 339 POWELL, H. E. and MILLER,C. K., 369, 393 SACKETT, W. M., 145 PRATT,W. E., 226, 250 SAID,R., 49, 145 PRAY,L. C. and MURRAY, R. C., 6, 20, 145 R., 211, 213, 214, 221 SANDER, PYTKOWICZ, R. M., 145, 195, 207 SANDER, B. and SACHS,G., 214, 221 SANDERS JR., J. W. and CRICKMAY, G. W., 4, RAMSDEN, R. M., 259, 338 20 RANKAMA, K., 327, 328, 336 K. and SAHAMA, T. G., 50, 86, 145 SASS,E., 145 RANKAMA, D. F., 326, 339. 372, 393 S. R., 145 SAUNDERS, RAO,M. S. and YOGANARASIMHAN, SCHARRER, K., 145 RAQUIN.E., 217, 221 NODDACK, I. and NODDACK, W., 53, 144 NOLL,W., 102, 144 NORTH,F. J., 292. 338

402

REFERENCES I N D E X

SCHLOEMER, H., 172,173, 190 SVERDRUP, H. U., JOHNSON, M. W. and FLESCHMALZ, R. F., 152, 166 MING, R. H., 2, 3, 20, 88, 147, 180, 186, 190 SCHMIDT, V., 146 SWAN,E. F., 68, 147 SCHMIDT, W., 213,221 SWETT,K., 147 SCHOFIELD, A. and HASKIN,L., 49, 146 SCHOLL, D. W., 146 TAFT,W. H., 95, 147 SCHUBERT, J., 73, 146 TAFT,W. H. and HARBAUGH, J. W., 4, 20, 74, SCHUMANN, H., 282,283,339 87, 95, 101, 115, 147, 151, 153, 158, 167, SCHWARTZ, F., 267, 339 325, 327, 329, 339 SCHWOB, Y.,317, 321, 323, 339 TASCH,P., 98, 147 SEIBOLD, E., 87, 146 TATSUMOTO, M. and GOLDBERG, E. D., 49, 71, SHARMA, G. D., 146 84, 91, 147, 328, 339 SHEARMAN, D. J., KHOURI,J. and TAHA,S., TAYLOR JR., H. P. and EPSTEIN,S., 199, 200, 96, 146 205, 207 SHOJI,R. and FOLK,R. L., 27,28,146,287,339 TAYLOR JR., H. P., FRECHEN, J. and DEGENS, SHORT,N. M., 254, 339 E. T., 195, 198, 204, 205, 207 SHINN,E. A. and GINSBURG, R. N., 152, 166 TAYLOR, J. H., 147 SIEGEL, F. R., 12, 20, 49, 65, 73, 96, 100, 103, TEICHERT, C., 147 108, 112, 146, 153, 167, 326, 339, 372, 393 TEICHM~LLER, M., KALIFEH, Y.and LOUIS,M., SILVERMAN, S. R., 198, 199, 207, 229, 250 211,222 SILVERMAN, S. R. and EPSTEIN,S., 194, 207 TENNANT, C. B. and BERGER, R. W., 324,339 SIMKISS, K., 58, 95, 146 TEODOROVICH, G. I., 11, 131, 147 SIPPEL,R. F. and GLOVER, E. D., 146 TEODOROVICH, G. I., SOKOLOVA, N. N., SKINNER, H. C. W., 87, 89, 110, 116, 146, 177, ROSSONOVA, E. D. and BAGDASSAROVA, 190, 325, 339 M. V., 96, 147 SKINNER, H. C. W., SKINNER, B. J. and RUBIN, TERRY,R. D. and CHILINGAR, G. V., 256, 339 M., 339 THODE, H. G., WANLESS, R. K. and WALLOUCH, R., 195, 207 SLOSS, L. L., 339 SLOSS,L. L. and COOKE,S. R. B., 289, 339 THOMPSON, T. G. and CHOW,T. J., 62,67, 147 SMITH JR., P. V., 228, 250 THUGETT, ST. J., 262, 263, 339 SMOLIN, P. P., 220, 221 THURBER, D., BROECKER, W. and KAUFMAN, SMYKATZ-KLOSS, W.,316,317,320,321,322,339 A., 328, 339 TIKHOMIROVA, SOKOLOV, V. A., 228,250 E. S., 124, 147 SPEARS, D. A., 146 TILLEY,C., 217, 222 SPOONER, G. M., 146 TISCHENDORF, G. and UNGETHUM, H., 147 SPOITS,J. H., 100, 146 TOURTELOT, H. A., 366, 393 STAUFFER, K. W., 288, 339 TREIBS,A., 227, 250 STEARN, G. W., 388, 393 TREFETHEN, J. M., 363, 393 STECHER, P. G., 377, 386, 393 TR~ER W., E., 281, 340 STEHLI,F. G., 202, 207 TUREKIAN, K. K., 79, 80, 108, 114, 147 STEHLI,F. G. and HOWER,J., 83, 87, 101, 146, TUREKIAN, K. K. and ARMSTRONG, R. L., 49, 61, 71, 104, 106, 107, 108, 147 151, 167 STENZEL, H. H., 58, 146 TUREKIAN, K. K. and KULP,J. L., 148 STERNBERG, E. T., FISHER, A. G. and HOLLAND, TUREKIAN, K. K. and WEDEPOHL, K. H., 148 H. D., 111, 146 TURNER, F. and VERHOOGEN, J., 222 R. M. and BELDING,H. F., 339 STERNBERG, TURNER, F. and WEISS,L., 211, 212, 213, 222 STEVENS, R. E. and CARRON,M. K., 339 STOWELL, F. R., 393 UREY,H. C., 199, 207 STRAKHOV, N. M., 146,260,261,262,263,264, UREY,H. C., LOWENSTAM, H. A., EPSTEIN,S. and MCKINNEY, C. R., 195, 198,207, 340 265, 266, 270, 279, 339 STRAKHOV, N. M., ZALMANZON, E. S. and USDOWSKI, H. E., 87, 91, 96, 97, 98, 101, 102, GLAGOLEVA, M. A., 118, 119, 120, 121, 147 148, 281, 340 STRIJVE, S., 216, 221 USPENSKIY, V. A. and CHERNYSHEVA, A. S., 232, STUIVER, M., 339 250 SUGAWARA, K., OKABE,S. and TANAKA, M., USPENSKIY, V. A., INDENBOM, F. B., CHERNYSHEVA, A. S. and SENNIKOVA, V. N.. 245,251 53, 147

REFERENCES INDEX

403

VALENTINE, J. W. and MEADE,R., 148 WHITE,D. E., HEM,J. D. and WARING,G. D., VALYASHKO, M. G., 5, 20 182, 190 VANDER WALT,c. F. J. and VANDER MERWE, WHITECROSS, M. I., 286 A. J., 302, 340 WHITMORE, E. C., 227, 251 VANNEY, J.-R., 148 WICKMAN, F. E., 148, 197, 207, 328, 340 VASSOEVICH, N. B., 225, 245, 251 WICKMAN, F. E. and VONUBISCH,H., 329,341 VEBER,V. V. and GORSKAYA, A. I., 244,251 WICKMAN,F. E., BLIX, R. and VON UBISCH, VEBER,V. V. and TURKELTAUB, N. M., 228, H., 341 251 WILBUR,K. M., 149 VINOGRADOV, A. P., 4, 20, 49, 52, 53, 55, 59, WILBUR,K. M. and JODREY,L. H., 329, 341 61, 74, 75, 148 WILBUR,K. M. and WATABE,N., 58, 149 VINOGRADOV, A. P. and BOROVIK-ROMANOVA, WILLARD, H. H. and GREATHOUSE, L. H., 300, T. F., 148 341 WILLIAMS, M. and BARGHOORN, E. S., 14, 198, VINOGRADOV, A. P. and RONOV,A. B., 11, 131, 132, 133, 148 207, 329 341 VINOGRADOV, A. P., RONOV,A. B. and RATYN- WILLIAMS, R. P., 149 SKIY, V. M., 134, 148 WILSON,R. L. and BERGENBACK, R. E., 149 VOGEL,A. I., 295, 297, 313, 315, 342 WINCHELL, A. N., 276, 341 VOGEL,J. C., 194, 195, 207, 329, 340 WINCHELL, A. N. and MEEK,W. B., 283, 341 VONDER BORCH,C., 148 WINCHELL, A. N. and WINCHELL, H., 350, 393 VON ECKERMANN, H., VON UBISCH,H. and WINDES,S. L., 351, 362, 363, 393 F. E., 198, 207 WICKMAN, WISMAN, J. D. H., 70, 87, 149 VON ENGELHARDT, W. 49, 148 WOBBER,F. J., 149 WOLF,K.H., 10,28,83,89, 100, 105,113, 149, WAITE,J. M., 325, 340 255, 257, 259, 260, 274, 276, 286, 287, 294, WALGER, E., 259, 282, 283, 286, 340 327, 341 WALKER, C. T., 28, 148 WOLF,K. H. and CONOLLY, J. R., 149,255,341 WANGERSKY, P. J. and GORDON, D. C., 148 WOLF,K. H., CHILINGAR, G. V. and BEALES, WANGERSKY, P. J. and JOENSUU, O., 148 F. W., 328, 341 WARNE,S., 259, 261, 266, 267, 268, 269, 270, WOLF, K. H., EASTON,A. J. and WARNE,S., 316, 317, 318, 320, 321, 323, 340 27, 75, 149 WARNE,S. and BAYLISS,P., 320, 323, 340 WOODRING, W. R., 149 WATABE, N. and WILBUR,K. M., 58, 105, 148, WOOLF,D. O., 351, 363, 393 286, 340 WRAY,J. L., 341 WATABE, N., SHARP, D. G. and WILBUR, K. M., WRAY,J. L. and DANIELS, F., 93, 95, 149, 153, 286, 340 167, 341 WATTENBERG, H. and TIMMERMANN, E., 88, 148 WYLLIE, P. J. and TUTTLE, 0. F., 149 WAUGH,W. N. and HILLJR., W. E., 361,364, 393 YANAT’EVA, 0. K., 5, 6, 20, 21, 178, 179, 184, WAYLAND, J. R. and HAM,W. E., 393 185, 191 WAYLAND, R. G., 286, 340 YOE,J. H. and ARMSTRONG, A. R., 301, 341 WEBB,D. A. and FEARON, W. R., 52,54,148 YUSHKIN, N. P., 149 WEBB,T. L. and HEYSTEK,. 316, 318, 340 WEBER,J. N., 28, 117, 149,329,340 ZARTMAN,R. E., WASSERBURG, G. J. and WEBER,J. N. and KEITH,M. L., 340 REYNOLDS. J. H., 195,207 WEBER,J. N. and LAROCQUE, A., 148,329,340 ZARITSKIY, P. V., 149 WEBER,J. N. and SMITH,F. G., 325, 340 ZELLER. E. J., 215,222,326, 341, 372, 393 WEBER,J. N., WILLIAMS,E. G. and KEITH, ZELLER,E. J. and PERN,W. C.,326,341 M. L., 329, 340 ZELLER,E. J. and RONCA,L. B., 372, 393 K. H., 53, 148 WEDEPOHL, ZELLER,E. J. and WRAY,J. L., 88, 92, 95, 103, WEEKS,L. G., 233, 237, 251 149, 326, 341 WEEKS,W., 217, 222 ZELLER,E. J., WRAY,J. L. and DANIELS,F., WEISS,A., 231, 251 326, 341 WELLER,J. M., 2, 20, 234, 251 ZEN,E-AN, 149, 341 WELLS,A. J., 177, 191 ZOBELL,C. E., 74, 149, 229, 251 WEYL,P. K., 195, 207 ZUMPE,H. M., 341

SUBJECT INDEX1

Abqaiq-Ghawar oil field, 235 Abrasive hardness of carbonate rocks, 362,363 Absorption of elements, 104, 105 - train, 297 Acid-etching, 256-258 Adsorption, 104, 105 Age dating, 14, 18, 84, 327, 328 - _ ,carbonates, zzsRa/238Umethod, 84 _ _,- U-10 method, 84 _ - , -, 234U/238Umethod, 85 _ _ , -, uranium-helium, 18, 328 _ _ , -,carbon-14, 327, 328 _ _,corals, 84 Algae, 30, 33, 37, 40, 43, 44, 47, 55-58, 60,62, 67, 68, 73, 78, 83, 88, 89, 98, 99, 105, 113, 255, 286 -, Chlorophyceae, 30, 34, 37, 40,44 -, Corallinaceae, 30, 34, 37, 40, 44, 47, 59, 67 _ ,- ,Sr/Ca ratio, 67 -, Phaeophyceae, 30, 34, 37, 40,43 -, Rhodophyceae, 30, 34, 37,40,44 Alteration, due to diagenesis-epigenesis, 9, ~

100-1 10

Ammonites, 234 Amphistegina radiafa, rare elements in, 80 Anhydrite, 237, 248, 267, 268 Ankerite, 260-265,281, 283, 315,321-324 -, DTA analysis, 321-323 Annelida, 33, 36, 38, 43, 46, 49, 55, 63 Antimony, 43-46, 51, 293 Antrim Shale, 239 Apparent specific gravity of carbonate rocks, 362, 363 Arab-D-Formation, 236 Aragonite, 4,9, 12, 14,27,54,55,57,83,86,88, 92-95, 97, 98, 100, 101, 117, 153-165, 177, 203, 260, 262-266, 268, 315, 320, 321, 323, 325, 349, 350, 352, 374, 386 -, DTA analysis, 319, 320 -, entropy structure, 94 I The help extended by Herman H. Rieke, 111, in preparing the index is greatly appreciated by the editors.

- inversion, 57, 100, 101, 203

-, Lake Bonney, 86

- needles, 97 - precipitation, 92-98 - preparation, 153 - recrystallization, 154-165 - thermodynamic stability, 95 Argon, 52 Arsenic, 30-33, 50, 52, 53, 293 Arthropoda, 32, 36, 39, 42, 46, 48, 55, 56, 63, 67,68 Asmari Limestone, 236 Atmospheric COz, 134, 135, 194-197 AustraIorbis glabratus, 69 Authigenic minerals, 28, 129 Azurite, 349, 350, 353, 375, 386

Bacteria, 24, 55, 56, 61, 72, 74.75, 88, 98, 229, 230 -, concentration of Ca and Mg, 61 -, decomposition of organic matter, 229, 230 -, direct influences on carbonates, 74 -, elements utilized by, 74 -, ooliths precipitation, 98 Banff Limestone, 239 Barite, 55 Barium, 30-33, 50, 52, 71, 81, 90, 92-94, 104, 106, 108, 130, 293 - content in molluscan shells, 71 _ _ _ Pacific sediments, 90 Barium/calcium ratio, 81 Beryllium, 30-33, 50, 52, 293 Biochemical fractionation in organisms, 73 Biogenic versus inorganic extraction of ac03 in sea water, 196, 197 Biological specificity of metal ions, 73 Bismuth, 30-33, 52 Bitumen, 33, 40,47, 232, 234, 245,246 Boron, 3, 30-33, 50, 52, 53, 81, 90, 128, 293 Brachiopoda, 32, 35, 38, 41, 45, 48? 55-57, 63, 65, 67,68, 70, 75, 78, 79, 81, 109, 110, 255 Breunnerite, 27, 260, 262, 263, 265, 266 Bromine, 3, 30-33, 50, 52, 293 Brucite, 173, 217, 218 - stability range, 173

405

SUBJECT INDEX

Bryozoa, 31, 34, 37, 40,44,55, 57, 59, 61, 63, 67, 68, 103,255,288 Building stone, 353 _ _ properties of limestone used in Kansas, 353 Bulk density of carbonate rocks, 354 Caddo Lime, 354 Cadmium, 33-36, 50, 52, 293 Calcite, 14, 27, 55, 59, 76, 83, 96-98, 100, 107, 116, 153, 155-157, 161-164, 174, 183, 185, 205,211,26&268,283,315,316,318 324-326, 349,350,352,371,374,386 -, DTA analysis, 315-320 -, thermoluminescence, 326, 371 -, variation of Po with composition, 283 Calcium, 30-33,52,90,131, 161, 164,205,290, 305, 306, 328 -, changes with geologic time, 131 - isotopes, 205, 328 Calcium/magnesium ratios (also Mg/Ca ratio), 10, 11, 77, 85, 99, 111, 113, 116, 117, 132, 133, 135, 165, 186, 187, _ _ _ , activity ratio, 180-188 _ _ _ , carbon dioxide indicator, 135 _ _ _ , changes with time, 11, 133 - _ - , Coorong lagoon, 117 - - -, distribution, 111, 117 _ _ _ , increase from shore, 113 - - _ , iso-Ca/Mg ratio lines, 85 _ _ _ , Precambrian sea water, 99 _ _ _ ,salinity effect, 116 _ _ _ , sea water, 186 Calvert Formation, 62, 64, 65 Canyon Limestone, 244 Carbon, 30-33, 52, 53, 246 - -14, 327, 328 - dioxide, 134-136, 194-197, 296, 297, 317322 _ - ,atmospheric, 134, 135, 194-197 _ _, biogenic, 197, 197 _ _ , determination of, 296, 297 _ _ , DTA analysis, 317-322 _ _ effect on Ca/Mg ratio of carbonate rocks, 134-136 - isotopes (13C/12C), 14, 165, 194-199, 229, 328, 329 - _ ,atmospheric COZ, 195-197 _ _ , bicarbonates, 195-197 _ _ , carbonate rocks, 195-197 _ _ ,fractionation in the carbonate system, 196, 197, 329 _ _ , organic matter, 229 _ _ , recrystallization of aragonite to calcite, 165 - _ , sediments, 328

_ _,skeletal materials, 197, 198 _ - ,soil gases, 195-197 _ _ ,uses, 329

Carbonate minerals, 7-13, 24-28, 83, 98, 102, 103, 115, 117, 151, 152, 165, 171-176, 280, 281, 292-315, 350, 352, 353, 362, 363, 368375,386 _ _ ,amorphous origin, 98 _ _ ,chart for determining ne, trigonal carbonates, 280 _ _ ,chemical analysis, 292-31 6 _ _ , classification, 315 _ _,composition of modern carbonate sediments, 115 - _ ,crystallographic data, 352, 353 _ _,fluid inclusions, 27 _ _, free energy, 368 _ _ , heat capacity, 368 - -, - of formation, 368 - _ , infrared absorption spectra, 372-375 _ _ , isomorphism, 26 _ - ,magnetic susceptibility, 369 _ - , melting and transformation temperatures, 367 - _ , metastable, 151, 152, 165 _ _,mineral assemblage in Coorong lagoon, 117 _ _ ,mineralogy control by inorganic processes, 83, 84 _ _ , minor elements, 27 _ _ , modulus of rigidity, 362, 363 _ _ ,-- rupture, 362, 363 _ _ ,non-carbonate components, 28 _ _ ,optical data, 350 _ _ , physical properties, 349 _ _ , physicochemical factors controlling composition, 24 _ _ , solubilities, 179, 367 - _ , solution, 103 - _ , stability, 171-176 _ _ , ternary systems, 370 _ - ,thermoluminescence, 326, 371, 372 _ _ , trace elements, 27 _ _ , uses, 386 _ _ , variation of no with composition, trigonal carbonates, 281 Carbonate rocks, aspects and statistics of economics, 343-348 _ _ ,bacterial carbonates, 194 - _ , calcium oxide/magnesium oxide ratio, 10 ,chemical alteration, 9, 100-110 _' _,- analysis, 292-3 15 _ _,- composition, 294, 360, 361, 364, 365 - _ , compressibilities, 355 - _ , compressive strength, 358, 362, 363

--

406 Carbonate rocks (continued) - _ , crushing strength, 358 - _ , deformation, 211-216 - _ ,dielectric constant, 360 - _ , economics, 343-348 - -, formation of source rocks, 237 _ _ , high temperature studies, 198, 204 _ _ , impact toughness, 362, 363 - -, isotopes, 13, 14, 15, 193-206 _ _ ,longitudinal bar velocity, 362, 363 --, magmatic and metamorphic rocks, 193 - -,physical chemistry of formation, 12, 15 1-167 - _ , physical properties, 348-360, 362, 363 - _ , Poisson's ratio, 362, 363 - _ , polycomponent systems, 286 - _ , porosity, 2, 354 - _ , relationship between organic matter and insoluble residue in, 232 - _ , reservoir, 348 - _ ,resistivity, 359 - _ ,rigidity, 357 - _ ,scleroscope hardness, 362, 363 - _ , shear waves, 357 - _ , solid solution and subsolidus relations, 366-371 - _ ,source rocks for oil, 235-248 - _ ,specific damping capacity, 362, 363 - _ ,spot tests for cations, 289-292 - _ , tensile strength, 362, 363 - _ , thermal conductivity, 359 - _ , - expansion, 354 - _ , uses, 18, 19, 373, 376-389 - _ , Young's modulus, 356, 362, 363 Carbonatites, 14, 195, 198-200 Caspian Sea, 228 Caves, 19, 92, 96, 387 Celestite, 79, 102 Cement, 105, 128-130, 344, 346, 347, 377 -, cryptocrystalline, 105, 287 -, environmentally induced changes, 128-130 -, production of, 377 -, world production, 347 Cephalopoda, 32, 36, 38, 42, 46, 48, 57, 63, 68 Cerium, 33-36 Cerussite, 19, 267, 349, 350, 352, 375, 386 Cesium, 33-36, 50, 52, 293 Charles Limestone, 239 Chemical alteration of carbonates, 9, 100-1 10 - analysis, 289-3 15, 364, 365 _ _ , absorption train, 297 - _ , acid insoluble residue, 297 - _ , aluminum, 304, 305 - _ , calcium, 305, 306 , carbon dioxide, 296 - -, chromium, 302, 303

--

SUBJECT INDEX

_ _,composite analysis of limestones, 364,365 _ _ , determination of moisture and loss on ignition, 296

_ _, ferrous iron, 309, 310 _ _ , magnesium, 307, 308 _ _ , main analysis of carbonates, 297-315

_ _ , major and minor element analysis, 292

_ - , manganese, 300, 301, 308 _ _ , phosphorus, 303, 304

_ _ , potassium, 310-313 _ _ , Recent and ancient carbonate rocks, 294 _ _ , Rz03 group, 298-300 _ _ ,scheme for carbonate rocks, 295 _ _ , silica, 297, 298 _ - ,sodium, 31G313 _ _ , some carbonate minerals, 316 _ _ , strontium, 310-313 _ _ , sulfur trioxide, 314, 315 _ _ , titanium, 301, 302 _ - , total sulfur, 313, 314 _ - , trace element analysis, 293

- composition of various carbonates, 294, 360, 361, 364-366 Cherokee Reservoir, 241, 242 Cherts, 201, 202, 258 -, 1 * 0 / 1 6 0 ratio, 201, 202 Chlorine, 3, 21, 33-36, 50, 52, 293 Chondrites, 199 Chordata, 55, 56, 68 Chromium, 33-36, 50, 52, 90, 118, 128, 293, 298, 302 Cipolin, 219, 222 Classification of carbonate minerals, 3 I5 Clay, 2, 29, 90, 229-231, 240, 248, 258, 274 (see also shale) -, Br/CI ratio, 29 -, CI/Br ratio, 29 -, organic matter of, 231 -, overburden pressure, 2, 248 - separation from carbonates, 276-279 Cobalt, 33-36, 50, 52, 53, 100, 106, 118, 293 Coccoliths, 58 Coelenterata, 31, 35, 38, 41, 45, 48, 55, 56, 62, 67 Collenia, 99 Compressibility of carbonate rocks, 355 _ _ _ _ , at high pressures, 355 _ _ _ _ , at low pressures, 355 Compressive strength, 358, 362, 363 Concretions, 105, 106, 128-130 Cone-in-cone structures, 102 Contamination, 74, 86 -, cosmogenous, 86 -, drill cores, 74 -, mechanical, 86 -, volcanic, 86

407

SUBJECT INDEX

Conversion, 101 Coorong lagoon, 110, 116, 117 Copper, 33-36, 50, 52, 53, 81, 85, 90, 118, 128, 293 Corals, 62, 65, 68, 71, 83 Correlation, based on composition, 85, 128 Crassostrea virginica, 8 1 Critical concentration ratio (aragonite/magnesium), 151, 158 Crushed stone, 377 Crushing strength, 358 Crustacea, 32, 36, 39,42,46,48, 61, 63,68 Cyanophyceae, 53 Deep Spring Playa, California, 183 Deformation of carbonate rocks, 15, 16, 21121 6 _ _ _ _ , mechanism of, 211-213 _ _ _ _, experimental analysis of, 213-216 Diagenesis (or diagenesissepigenesis), 1 I, 15, 75, 99-110, 183, 184, 186, 198, 202-204 -, alteration, 75 -, - by fresh water, 109 -, chemical and physical changes, 106-110 -, conversion, 101, 102 -, diagenetic dolomitization, 11, 15, 110, 183, 184, 186, 202-204 -, grain growth and diminution, 101-102 -, inversion, 100 -, 1 8 0 / ' 6 0 alteration during, 202 -, 1sO/160change in brachiopods, 109, 110 Dielectric constant, 360 Differentiation of carbonates and trace elements, 113 Dilatometry, 214 Dolomite, 5, 13, 169-191, 199-204, 378-384 -, chemical requirements, 378-384 -, chemistry of formation, 13, 14, 169-191 -, COZeffect on formation, 169, 185, 186 -, DTA analysis, 321, 322 -, Eh effect on formation, 188 -, equilibrium conditions, 171-174 -, metasomatism of calcite, 202, 203 -, origin of, 202-204 -, 180/1e0 ratio of, 199-203 -, pH effect on formation, 188 -, physical requirements, 378-384 -, precipitation, 177-178 -, pressure effect on formation, 169, 187, 189 -, solubility, 170, 174-176, 178, 179, 184, 185 -, stability, 171-174 -, stable isotope distribution, 193-206 -, synthesis experiments, 176, 177, 187 -, temperature effect on formation, 169, 181, 187, 189

-, uses, 378-384

Dolomitization, 11, 15, 110, 183, 184, 186, 198, 202-204 Drewite, 89 Dundee Limestone, 236 Duvernay Shale, 235, 239 East Twin Lake, 114 Echinodermata, 33, 36, 39, 42, 46, 49, 5 5 , 59, 63, 67, 68 Echinoidea, 33, 36, 39, 42,46, 49, 57, 63, 78 Economics of carbonate rocks, 343-348 Elastic parameters of carbonates, 356, 357 _ - _ _ , ordinary pressure and temperature, 356 _ _ _ _ ,4,000 kg/cm2 and 30°C, 357 Elemental composition of carbonates, 7-10, 23-149 _ _ _ _ ,carbonate skeletons, 25, 3049, 57-71, 76-84, 98, 99 _ _ _ _,concentration through metabolic processes, 72 _ _ _ _ , diagenetic alterations, 75, 76, 106-1 10

_ _ _ _ ,direct bacterial influences, 74, 75 _ _ _ _ , inorganic processes determining, 25, 85-98

-__-

, metamorphically mobilized elernents, 130 _ _ _ _ , organic matter of organisms, 5254, 71-74 _ _ _ _, physicochemical factors determining, 24 _ _ _ _, poisonous elements, 105 _ _ _ _ , uptake of elements by shells, 7582 Ellenburger Limestone, 236 Environment, 76-85, 97-99, 109 -, hypersaline and hyposaline effect on skeleton composition, 81, 109 -, influence on particle form of carbonate precipitates. 97, 98 -, inorganic precipitation, control of, 92-97 -, regional trends in skeletal mineralogy, dependence on, 83, 84 -, salinity and temperature influences on composition, 76-82 Epigenesis, see diagenesis-epigenesis Equilibrium constants, 169, 178-181, 183, 185, 189, 205 Erbium, 33-36 Espiritu Santo Island, 4, 167 Etching figures, 213, 215 Europeum, 33-36 Experiments, 2, 69, 75, 88, 92-98, 153-164, 176-181, 184, 185, 187, 248

408 Experiments (continued) -, aragonite preparation, 153 -, - shell uptake of strontium, 69 -, calcium carbonate deposition in caves, 92, 96 -, - -precipitation controlled by impuiities, 92-96 -, dolomite synthesis, 176180 -, inorganic precipitation of calcium carbonate, 88, 92-98 -, overburden pressure effect on porosity, 2, 248 -, particle form of carbonate precipitates, 97, 98 -, recrystallization of aragonite to calcite, 153-164 -, shell growth, 75 -, solubility, 178-181, 184, 185, 187 -, *%r and 45Ca isotopes in aragonite and calcite precipitates, 69 -, Sr/Ca ratios in precipitates, 88 -, vaterite precipitation, 94-96 Exploration philosophies, 85 Feigl’s solution, 270, 272 Florida Bay, 230, 232 Florine, 33-36, 50, 52, 293 Fluid inclusions, 27 Flux, 361 Foraminifera, 31, 34, 37, 40, 44,57, 5941, 67, 68, 70, 71, 83, 103, 211,287, 325, 328, 329 Forsterite, 217, 218 Fractionation in organisms, biochemical, 73 -, isotope, 193-205 Free energy calculations: dolomite, calcite, magnesite, 171-175, 177, 178 - _ of formation of carbonate minerals, 368 Frontier Shale, 239 Gadolinium 3639 Galena, 100 Gallium, 36-39, 50, 118, 293 Garnier River, 214 Carrels technique, 189 Gastropoda, 32,36,38,42,46,48,57,63,67,78 Germanium, 36-39, 50, 52, 293 Gibbs conditions of equilibriumand freeenergy calculations, 171-178 Glauconite, 274 GlobiKerina, 31, 34, 37,40,44,47, 79, 83, 136 Goethite, 55 Gold, 3C33, 50, 52, 293 Grain deformation, 21 1-213 - diminution, 101-102 - growth, 101-102 Great Salt Lake, Utah, 88, 114

SUBJECT INDEX

Greenhorn Limestone, 354 Guil Valley, France (Guillestre Marble), 214, 215 Gulf of Batabano, 230 Gypsum, 86, 262, 267, 268 Hankinite, 218 Harrodsburg Limestone, 115 Heat capacity of carbonate minerals, 368 - of formation of carbonate minerals, 368 Heath Limestone, 244 Helium, 52 Hematite, 255 Hemichordata, 55 Holmium, 3639 Hydrocarbons, 225-248 -, allochthonous, 245 -, analysis of, 239 -, autochthonous, 245 -, catalytic generation, 232, 247 - derived from living organisms, 226229 - distribution in non-reservoir rocks, 238,239 - - in Recent and ancient sediments, 240 - _ - source-reservoir facies, 241 - generation from organic matter, 229-232 -, liquid hydrocarbons in Recent sediments, 228 -, ratio of odd- to even-numbered n-paraffins in sediments and crude oils, 244 Hydrogen, 36-39, 52 Hydromagnesite, 13, 87, 117, 172, 174-177, 186, 188 Impact toughness, 362, 363 Inclusions, fluid, 27 Indium, 37-39, 50 Infrared absorption spectra of carbonate minerals, 372-375 - reflection spectroscopy, 214 Inorganic precipitation of calcium carbonate, 86, 92-98 Insoluble residue, 123, 127, 232 - -, relationship with organic matter and bitumen contents, 232 _ _ , variation with time in carbonate rocks, 123, 127 Intercrystalline gliding, 212 Intracrystalline gliding, 212 Inversion, aragonite to calcite, 57, 84, 100, 101

Iodine, 36-39, 50, 52, 293 Ions. interference in determinations of, 310 Ireton Limestone, 239 Iron, 33-36,50,52,53, 101,105,124, 128. 290292, 298, 299, 309, 310 Isomorphism, 26

SUBJECT INDEX

Isotope geochemistry, 14, 15, 193-208, 279, 328, 329 _ _ , calcium and magnesium, 205, 206, 328, 329 _ _ ,carbon, 194199,204 _ - , carbonate sediments, 328, 329 --, distribution of carbon in carbonates, 194199,204 _ _ ,- - oxygen in carbonates, 199-203 --,fractionation, 193-205 --, magnesium, 206, 328 - -,high-temperature carbonates, 196, 198, 200,203,204 --,oxygen, 199-205, 279, 328, 329 _ - , W C relationship between coexisting dolomites and calcites, 204 _ _,613Cvalues in carbonaceous chondrites, 199 --, P O relationship between coexisting dolomites and calcites, 201-203 Joana Limestone, 85 Jubaila Formation, 236 Ketona Dolomite, 365 Kimmeridgien Limestone, 244

La Luna Limestone, 236, 243 Lake, Sr/Ca ratio in, 114 - Beloved, U.S.S.R., 6 - Mendola, 114 Lanthanum, 36-39, 50 Larnite, 218 Lau, Fiji, 4 Law of minimum in ecology and geochemistry, 82, 83 Lead, 39-43, 51-53, 92, 93, 100, 118, 293 Leavenworth Limestone, 364 Lee-Hedberg technique, 276 Lime, production of, 377 (see limestone and dolomite) Limestone, 209, 210, 361, 364, 365, 378-384, 387 -, chemical composition of, 364, 365 -, chemicalrequirements in their use, 378-384 - flux, 361 -, formation of, 209, 210 -, organic matter in, 71, 72, 238-242 -, physical requirements in their use, 378384 -, uses of, 378-384, 387 Lingulepsis, 69 Linnaeite, 100 Lithium, 37-39, SO, 51, 293 Lithothamnion, 83, 294 Longitudinal bar velocity in carbonate rocks, 362, 363

409 Macroporella, 217 Madison Limestone, 239 Magnesite, 5 , 87, 172-176, 180, 187, 188, 260268, 315, 317-320, 323, 349, 350, 352, 374, 386 -, DTA analysis of, 317-320 - stability range, 173, 187 -, thermogravimetric analysis, 323, 324 Magnesium, 3, 15, 39-43, 52, 59, 77, 79, 87, 90, 95, 101-103, 107, 111, 115, 131, 158, 186,205, 206, 217,291, 307, 308 - compounds, uses of, 376 - concentration in sea water, 3, 186 -, determination of, 307, 308 - in inorganic carbonates, 87 -, isotopes of, 205, 206 - relationship to temperature, 77, 78 -, spot test for, 291 Mg/Ca ratio, see Ca/Mg ratio Magnetite, 55 Malachite, 19, 349, 350, 353 Mammoth Cave, Kentucky, 387 Manganese, 39-43, 50, 52, 53, 81, 90,101,I105, 108, 118-124,291-295, 300, 301, 308, 387 Maracaibo Basin, 236 Marble, 18, 193, 210,222, 345, 354360 -, defined, 222 - Falls Formation, 365 Medway White Chalk, 364 Melting and transformation temperatures of carbonate minerals, 367 Mercury, 36-39, 50, 52,293 Menvinite, 218 Metabolic processes,concentration of elements, 72 Metal ions, concentration, stability of complexes, and biological specificity, 73 Metamorphism, 216-220 --,Bowen’s series, open and closed systems, 218,219 -, contact, 216, 217 -, regional, 217-220 -, reorientation of calcite, 216 -, selective, 218 Metastable carbonate minerals, 151, 152, 165 Michigan Basin, 236 Micrite, 114, 210, 211 -, recrystallization, 114 Microorganisms, 6 Migration of petroleum, 233-235 Millerite, 100 Minerals, see individual names -, authigenic, 28 Mirabilite, 86 Mission Canyon Limestone, 239 Modulus of rigidity, 362, 363

410 Modulus of (continued)

_ _ rupture, 362, 363

Mollusca, 32, 36, 38, 42, 45, 46, 48, 55-57, 59, 61, 63, 67, 68, 71, 82, 102 Molybdenum, 3943, 52, 53, 293 Mytilus califomianus, 76, 77 -, edulis, 76, 77 Neodymium, 3 9 4 3 Nesquehonite, 172-174 -, stability range, 173 Neutron activation, 293 Niagara Dolomite, 365 Nickel, 39-43, 51-53, 90, 100, 118, 128, 293 Niobrara Shale, 239 Nitrogen, 3943, 52, 58 Nodules, 91. 105 (see also concretions) Nordegg Shale, 239 North Wales Limestone, 364 Nubrigyn Reef Complex, 113 Oil, crude, composition of, 227 Ooid, 91, 97, 98 chemical composition of, 91 Oolite, 84, 88, 89, 91, 97, 98, 101, 210, 247, 258 -, environmental influences, 97, 98 Oolith, 75, 98 -, bacteria causing precipitation of, 98 Optical data on carbonate minerals, 279-283, 350 Oread Limestone, 364 Organic influences on elemental composition, 24, 25 - matter, 71-74, 229-231, 238-242, 246 - _ , bacterial decomposition, 229, 230 - _ , composition, Cherokee Group of Kansas and Oklahoma, 242 - _ ,environment, effect on amount of, 238 _ _, generation of hydrocarbons from, 229232 - _ , in carbonate source rocks, 238-242 _ _ _ limestones, 71 _ _ _ non-reservoir rocks, 239 _ _ _ Recent and ancient sediments, 240 _ - _ _ clastic sediments, 231 _ _ _ _ marine sediments, 240 _ _ _ shales, 71 _ _ , relationship between total Corg and soluble bitumens, 246 - _ , - to insoluble residue, 232 - _ variation in content with particle size, Viking Shale, 231 Organism, shell secretion, 58 Orinoco Delta, 230 Overburden pressure, effect of, 2,210,211,248 Oxygen, % weight of organisms, 52

-.

SUBJECT INDEX

- isotopes (180/le0 ratio), 69, 79, 109, 110, 165, 194, 199-205, 328, 329 _ _, diagenetic changes, 109, 110 _ _ , Globigerina ooze, 200 _ _ in brachiopods, 79 _ _ _ carbonates, 199-203 --- carbonate sediments, 328, 329 _ _ _ dolomitexalcite pairs, 201-205 _ _ _ formation waters, 203 _ _ , paleotemperature curve, 200 _ _ , recrystallization of aragonite to calcite, 165 _ _ , uses of, 329 _ _ , variation with age, 201, 202 Paluxy Formation, 365 Peel techniques, 272-274 Pelecypods, 32, 36, 38, 42, 45, 48, 67, 68 Peridiniaceae, 53 Permian Basin, 236 Persian Gulf, 151 Petroleum, 16, 17, 225-248 -, migration of, 233-235, 245 -, origin of, 16, 17, 225-248 -, source rocks of, 235-248 Phanerozoic, 25 Phosphate, in Russian platform sediments, 125-1 27 Phosphatic material in shells, 55, 56, 69 Phosphoria Formation, 365 Phosphorite, 125 Phosphorus, 3943, 52, 118, 124, 162,298, 303, 304 -, chemical analysis for, 303, 304 - in Russian platform sediments, 118-120, 125-127, 128 Physical properties, 348-360, 362, 363 _ _ of carbonate minerals, 349 _ - _ carbonate rocks, 348-360, 362, 363 Physicochemical factors determining elemental composition, 24 Plankton, 53 Plattsmouth Limestone, 364 Poisson’s ratio, 360, 362, 363 Polymorphism, 57, 66, 82, 83, 98, 99 Porifera, 31, 35, 38, 41, 44, 47, 5 5 , 56, 62, 65, 67, 68, 255 Porosity, 2, 248, 354 Porphyrins, 72, 227 Portland cement, production of, 377 Potassium, 3, 37-39, 50, 52, 98, 162, 293, 310312 -, chemical analysis for, 31C312 Post-mortem concentration of elements, 72 Praseodymium, 3 9 4 3 Precipitation, 86,92-98, 105, 106, 153,177-180

41 1

SUBJECT INDEX

- of aragonite, 92-98, 153 _ - calcite, 92-98 _ - carbonate cement and nodules, 105, 106 _ _ dolomite, 92, 177-180 _ - vaterite, 92, 94, 97, 98 -, physicochemical inorganic, 86 Pressure, influence, 2, 169, 187, 189, 209-222, 248 -, - of load, overburden, 2, 210, 21I , 248 -, - on dolomite genesis, 169, 187, 189 Proteins, 9, 72, 229, 230, 241 Protodolomite, 13, 152, 153, 176, 177 Protozoa, 31, 34, 37, 40, 44, 55, 56, 61, 67 Pteropod shells, 68, 108 Pyrite, 129, 130, 361 Pyroxene, 218 Quirke Lake, Ont., 54 Quarries, 388 Quartz, 2, 129, 130, 205, 207 (see silica) Radiolaria, 79 Radium, 39-43, 51, 84, 293 - isotopes, 84, 85 Recrystallization, 100, 109, 112, 151, 152, 1 5 4 165, 212, 213 - effect of calcium ion, 160, 161 _ - - magnesium ion, 156160 _ _ - other ions, 162, 163 -, influence of chemistry and temperature, 154, 155 - of aragonite to calcite, 100, 154-165 - _ vaterite, 162, 164 -, post-tectonic, 213 -, rate of, in distilled water, 154, 155, 158 -, Riecke’s principle, 212 -, solid state, 151, 152, 165 -, syntectonic, 213 Reorientation of calcite, with dynamic metamorphism, 216 Replacement, dolomite, 183, 184, 202, 203 Reservoir rocks, carbonate, 348 Resistivity, 359 Rhenium, 43-46 Rhodochrosite, 19, 27,264,267,269, 281-283, 349, 350, 352, 374, 386 Riecke’s principle, 212 Rigidity of carbonate rocks, 357 Rogers City Limestone, 236 Rubidium, 4346, 51, 52, 293 Russian platform, 120-128, 131-133 Salinity, relation to skeletoncomposition, 80-82 Samarium, 4 3 4 6 Sand, 2, 10, 119, 123, 130, 213, 231, 258 Sandstone, 126, 130, 133, 242

Sauwand Limestone, 111, 112 Scandium, 4346, 51 Scapolite, 219 Schist, 217 Schotter flask, 296 Schumann method, 282 Scleroscope hardness of carbonate rocks, 362, 363 Sea water, composition of, 2, 3, 186 Selenium, 4346, 51, 52, 293 Serpula tubes, 59, 60,63 Shale, 90, 234, 239, 242, 247 Shear waves in carbonate rocks, 357 Siderite, 27, 129, 205, 260-265, 267, 281-283, 294, 315, 316, 317, 322, 324, 349, 350, 352, 367, 369, 374, 386 -, DTA analysis, 3 16, 3 17, 3 19, 322 -, staining, 260-265, 267 Sideroplesite, I30 Silica (SiOz), 127, 129, 297, 298 -, chemical analysis for, 297, 298 - in carbonate rocks of Russian platform, 127 Silicon, 4346, 52, 72 Silver, 30-33, 50, 52, 53, 293 Simpson Shale, 236 Skeletal mineralogy, 8,9,24,54,55,57-63, 6567, 69, 75-84, 106-109 _ _ , aragonite, 57-59 _ _,calcite, 57-59 _ _ , distribution according to phylum, 55 _ _ , environment, influence of, 82, 83 _ _ ,factors determining, 54 _ _ , geological problems, application of, 75 _ - , regional trends in, 83, 84 - _ , taxonomic significance, 75 _ - , temperature indicator, 76, 77 Skeleton composition, 25, 3 M 9 , 57-71, 7684, 98, 99 _ _ , magnesium content, 59-61, 77, 78 - -,strontium content, 61-70, 78, 79 Smithsonite, 19, 266, 267, 349, 350, 352, 375, 386 Sodium, 3, 21, 3943, 51, 52, 92, 98, 128, 162, 293, 310 Solnhofen Limestone, 355-359, 365 Solid solution and subsolidus relations, 366-371 Solubility, 2.3, 174-176, 179-185, 187,367 -, calcite-dolomite equilibrium, 181 -, calcite dolomite and magnesite dolomite, 187 -, CaC03-MgC03-HzO system, 5 -, dolomite, 174-176, 178, 179, 183-185, 187 -, Mg/Ca ratio in ground waters, 182 -, various components in sedimentary rocks, 2, 3 Solution, leaching and bleaching, 103, 104

+

+

412 Source rocks, 235-248 --,comparison of carbonates and shales, 247 _ _ , distribution of organic matter in, 238242 _ _ , examples of, 235-237 - -, geochemical techniques for recognition Of, 242-246 Sparite, 15, 210, 21I , 288 Species effect, in composition of skeletons, 58 Specific damping capacity of carbonate rocks, 362, 363 - gravity, apparent, 362, 363 Spectral well logging, 128 Spectrometry, 293 Spectrophotometry, 293, 295, 299-304, 309315 Spergen Formation, 365 Sphalerite, 100 Spherulite, formation, 97, 98 Spongiostromata, 276 Spot tests for cations, 289-292 Springer Shale, 239 Spurrite, 218 Stability of carbonate minerals, 171-174, 187 Staining, 259-272 -, alizarin red, 262, 267, 270, 271 -, determination of isomorphous series, 282 -, Feigl's solution, 263, 272 -, Harris' hematoxylin, 268, 272 -, iron content in calcite, dolomite and ankerite, 271 - solutions, 260-269 -, titan yellow, 268, 272 Stalactites, 388 Stalagmites, 388 Steinplatte Limestone, 111, 112 Stone, production of, 343, 351, 353, 373, 377 Stress, influence on carbonate rocks, 21 1-216 Stromatactis, 255 Stromatolites, 56 Strontianite, 19,27,89, 102, 263,267,315,320, 323, 325, 349, 350, 352, 375, 386 Strontium, 3, 43-46, 51, 52, 65-67, 69, 78-82, 87-97, 100-115,118,119,130,132,133,162, 163, 165,290, 293,294, 310, 311 -, chemical analysis for, 310, 311 - in inorganic carbonates, 87-97 - in skeletons, 61-70, 78,79 -/calcium ratio (also Ca/Sr ratio), 8,9, 11, 12, 62-70,78-82,87-90, 101,102,112-116, 133, 165 - - _ ,factors affecting, in organisms, 64 - - _ in Algae, 62, 89 - - _ _ carbonates, 65 - - _ _ cemented beach sands, 89

SUBJECT INDEX

----corals, 62, 67, 68 ---- fossil shells, 81, 82

_ _ - _ fossils and rock matrix, 70, 101 _ _ _ _ gastropods, 63, 64,67

_ _ _ _ organisms, 62-70,

78-82, 101,102

_ _ _ _ pelecypods, 63,64,67 _ _ _ _ precipitates, 87-89 _ _ _ - sea water, 88 _ _ - _ sediments, 90, 112-115 -,- - - tissue, 68 _ _ _ , iso-strontium/calcium ratio lines, 112 ---, marine versus fresh-water sediments, 114

__-__ _-___--

, recrystallization, effect on, 101, 165

,sedimentary cycle, 113 , temperature effect on, 78, 79 , salinity effect on, 8&82

, variation with geologic time, 133 Sulphur, 43-46, 52, 313, 314 -, chemical analysis for, 313, 314

Talc, 217, 218 Techniques in analyzing carbonates, 17, 18, 214,215, 242-246, 253-329 _ _ _ - , acid etching, 256258 _ - _ - , - insoluble residue, 297, 298 _ _ _ _ , differential thermal analysis, 315323 _ _ _ _,diolatometry, 214 _ _ _ - , electron microscope, 286, 287 _ _ - - ,etching figures, 215 _ _ _ - , field studies, 254, 255 _ _ - - , geochemical, for recognizingsource rocks, 242-246 _ _ _ - ,infrared reflection spectroscopy, 214 _ _ - - , introduction, 17, 18 _ _ - - , isotopes, 328 _ _ _ _, moisture and loss on ignition, 296 _ - _ _ , peel, 272-274 _ - - - ,optical identification,279-283,286 _ _ _ _, oxidation method for determining source rocks, 244 _ _ _ _,radiocarbon dating, 327, 328 _ _ _ - , separation of insolubles, 274-279 _ _ _ _,- _ clay, 276279 - _ _ _ ,spectrophotometricmeasurements, 295, 296, 299-305, 309-314 _ _ _ _, spot tests for cations, 289-292 - _ _ _ , staining, 259-272 ----, statistical and microfacies studies, 287-289 _ _ _ - ,thermogravimetric analysis, 323, 324 _ _ _ _ , thermoluminescence, 215, 216, 326, 327

413

SUBJECT INDEX

Techniques in analyzing carbonates (continued) ---_ ,trace-element analysis, 293 - _ _ _ , universal stage, 213 - - _ _ , X-ray diffraction, 214, 324, 325 - - _ _ , - radiography, 289 Temperature, 76-79, 154-161, 163-165, 169, 181, 187, 189, 204, 205 -effect on dolomite formation, 169, 181, 187, 189 - _ - equilibrium constant, 204, 205 - - _ recrystallization rate, 154-161, 163165 - -magnesium relationship, 77, 78 - -mineralogy relationship, 76, 77 - -strontium relationship, 78, 79 Tensile strength, 362, 363 Terbium, 43-46 Ternary systems, 370 Thallium, 47-49, 52 Thermal conductivity, 359 - expansion, 354 Thermogravimetric analysis, 323, 324 Thermoluminescence, 215, 326, 327, 371, 372 Thorium, 47-49, 51, 293 Thulium, 4 7 4 9 Tilleyite, 218 Time, importance in reactions, 12, 153 Tin, 43-46, 51-53,293 Titanium, 47-49,52, 53,90, 127, 128,292,293, 298, 301, 302 - determination of, 301, 302 Toronto Limestone, 364 Traverse Limestone, 236 Tremolite, 218, 219 Trenton Limestone, 236 Trilobita, 36, 39, 42, 46, 57 Trona, 19, 375, 386 Tungsten, 4749, 51, 293

Young's modulus, 356, 362, 363 Ytterbium, 4749, 51 Yttrium, 47-49, 73

Universal stage, 213 Uranium, 18,29,4749, 51, 71, 84, 85,91, 293, 328 -, syngenetic, 91

Zechstein Dolomite, 239 Zechsteinsalzen rocks, 90 Zinc, 4749, 51-53, 100, 118, 293 Zirconium, 47-49, 51, 90,293

-/calcium ratio, 84 --helium, age determination, 18, 328 Uses of carbonate minerals, 386 - _ _ rocks, 18, 19, 373-389 Vanadium, 47-49, 51-53, 90,106, 118, 293 Vaterite, 94, 96, 98, 162, 164, 325 -, recrystallization, 162, 164 Viking Shale, 230 Viscan Limestone, 245 Viviparus, 58 Water, 2, 3, 180-186, 200 -, sea, 2, 3, 186, 200 -, subsurface, 180-182, 185, 186 -, surface, 183, 184 Weber Sandstone, 242 Wilcox Shale, 239 Williston Basin, 235 Whiting, uses of, 385 Witherite, 19, 27, 263, 267, 268, 315, 320, 323, 349, 350, 352, 375, 386 -, DTA analysis of, 320 Woliastonite, 217, 218 Woodford Shale, 239 X-ray, 2, 17, 18, 153, 176, 180, 213, 214, 275, 277, 278,289, 318, 324-327, 366 -, crystal deformation, 213 - diffraction, 324-327 -, overburden pressure, 2 - radiography, 289 - spectrograph, 293 Xenomorphic, 210

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