RETURNING MATERIALS: IV1ESI_J ETEce in book drop to LIBRARIES III-lfl-I-L *— remove this checkout from your record. FINES w111 be charged if book is returned after the date stamped be10w. “7‘ 6/2X SYNTHETIC DOLOMITE TEXTURES By Susan Brook Bullen A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Geology 1983 ABSTRACT SYNTHETIC DOLOMITE TEXTURES By Susan Brook Bullen Selective dolomitization of carbonate rocks is common in nature. Experiments in this study were conducted to test the effect of precur- sor crystal size and mfineralogy on relative rates of dolomitization and textures of dolomitized fossils. Cryptocrystalline and microcrystalline carbonate skeletal fragments composed of high Mg-calcite (HMC), low Mg-calcite (LMC) or aragonite. (ARA) were hydrothermally altered at 250°C. The artifically produced dolomites showed distinct textural similarities to natural dolomites. Cryptocrystalline skeletal materials composed of HMC and LMC were more readily dolomitized than microcrystalline substrates composed of LNG or aragonite. LMC was as readily dolomitized as HMC in cryptocrys- talline fossils whereas microcrystalline LMc resisted dolomitization. Aragonite converted readily to dolomite at the skeleton-dolomitizing solution interface or to LMC in the fossil interior. Mimic replacement was observed in cryptocrystalline substrates composed of HMC and LMC. ACKNOWLEDGEMENTS First and foremost, I would like to thank Duncan Sibley for being wonderful fellow throughout the entirety of this project. He was much more than a professor with good ideas. I thank him for all the time and effort put into this project, for his support and friendship. It was a pleasure working for him. I would like to thank Dave Long and John Hilband for serving on my committee. Dave was meticulous in making comments and criticisms of the study. John deserves special thanks for the many hours he spent helping me with the X-ray diffraction unit and keeping it in working order. At Amoco, I would like to thank Pete Smith for his advice and support, Wayland Roberts for S.E.M. training, Jane Naites for her technical expertise and help in using the S.E.M. analytical spectro- meter, Joe Finneran for help in photographing thin sections, and Art Schwenk for film processing. I would like to thank A.A.P.G. Grants-in-Aid and Amoco Production Company for their support in this endeavor. Finally, I would like to thank my dear friends Bud Moyer, Ben Schuraytz, and Kazuya Fujita for all the special times that friends share when they're living for their work but still mflssing all the things that are lacking in their lives. 11 List of Figures Previous Experimental Studies Previous Petrographic Studies Conclusions Future Work TABLE OF CONTENTS List of Tables ....................... Introduction ........................ Experimental Procedure ................... Results Coralline Algae . . ................. . . Echinoid . . . .......... . . . ........ Forams . . . ...... . ............ . . . . . Coral . . ....................... GastrOpod ........................ Pelecypod . . . . . . . . . . ............. Discussion Dolomitization of Cryptocrystalline Substrates ..... Dolomitization of Microcrystalline Substrates ..... Comparison of Synthetic and Natural Dolomites ..... Mimic Replacement During Hydrothermal Dolomitization . . . . Appendices ......................... Bibliography ........................ Page iv 108 109 111 120 122 127 180 TABLE TABLE TABLE TABLE TABLE TABLE TABLE TABLE TABLE LIST OF TABLES Page Composition and grain size classification for skeletal materials ...................... 6 Experimental parameters ............... 9 x-ray diffraction results for experimentation on corralline algae ....... . ........... l4 X-ray diffraction results for experimentation on echinoids . .......... . . . ........ 29 Microprobe results for experimentation on forams . . . 54 X-ray diffraction results for experimentation on corals .................. . ..... 64 X-ray diffraction results for experimentation on gastropods ......... . ............ 74 X—ray diffraction results for experimentation on pelecypods . . . . ........... . ...... 88 Conclusions of study ................. 123 iv LIST OF FIGURES Page Figure l. Stability fields for magnesite, dolomite and calcite . 7 INTRODUCTION The differential response of various fossils to dolomitization has been used to infer the mineralogy of fossils at the time of dolomitiza- tion (Schofield and Nelson, 1978; Buchbinder, 1979; Sibley, 1980 and 1982). This differential response might reflect mineralogy and/or crystal size of the material being dolomitized. This study examines the effects of mineralogy and crystal size on the texture of syntheti- cally dolomitized fossils. The experimental conditions employed in this study are vastly dif- ferent (TsZSD’C) from the conditions under which dolomite usually forms. There is no way to rigorously ascertain the effect of this dif- ference on the applicability of our results to sedimentary dolomite textures. Rock textures are a function of crystal nucleation and growth which are, in turn, determined by the solution and substrate. He have to infer the relative importance of the processes and variables through experiments and petrographic analysis. As discussed below, we conclude that our experiments are applicable to sedimentary dolomite because 1) the textures produced in artifical dolomites are similar to those found in natural dolomites and 2) the results are consistent with inferences made from petrographic analysis of natural dolomites. PREVIOUS EXPERIMENTAL STUDIES Previous experimental studies provide some insight into the rela- tive rates of dolomitization of low Mg-calcite (LMC) and aragonite (ARA), but the experiments were not designed to test the rate of dolo- mitization as a function of both mineralogy and crystal size of the reactants. Katz and Matthews (1977) showed that ARA is dolomitized faster than LMC at 252°C, but they did not specify the relative surface area of the reactants. Grethen (1979) dolomitized LMC at 150°C and found the rate of dolomite formation is directly related to surface area of LMC. He also dolomitized HMC and ARA but it is not possible, with his data, to evaluate the effects of mineralogy on the rate of dolomite formation because the ARA and HMC were impure and had differ- ent surface areas. Gaines (1980) reports the following relative rates of dolomitization: ARA > HMC > LMC. Again surface areas of reactants were not determined. Gaines (1980) also found that the addition of protodolomite to the reactants increased the reaction rate. He concluded that nucleation of the dolomite phase is an important factor in the reaction kinetics. Katz and Matthews (1977) seeded some of their experiments with synthet- ic dolomites and found no appreciable effects. Perhaps the disordered surface of protodolomite is a more efficient nucleant than the more ordered surface of dolomite. PREVIOUS PETROGRAPHIC STUDIES Lime mud is often more susceptible to dolomitization than calcite spar (Murray and Lucia, 1967) and aragonite (ARA) and HMC are more sus- ceptible to dolomitization than LMC (Steidtmann, 1911; Fairbridge, 1957; Schmidt, 1965; Schofield and Nelson, 1978; Buchbinder, 1979; Armstrong, et. al., 1980; Baker and Kastner, 1981; Sibley, 1982). These inferred relative susceptibilities are based on petrographic interpretations which can be ambiguous. For instance, a selectively dolomitized coralline algal fragment (thin section 1) could be attrib- uted to the fossil's fine crystal size, permeability, or original mineralogy (HMC). Another sample collected within a few meters of the sample shown in thin section 1 has a generation of LMC cement which preceded dolomitization. We interpret the LMC to indicate a period of freshwater diagenesis preceded dolomitization and, therefore, the fossil in thin section 1 probably converted to LMC prior to dolomitization. Obviously, assessment of dolomite selectivity based on petrographic analysis is difficult. 0n the other hand, correct interpretation of dolomite selectivity may be useful for inferring the pre-dolomitization diagenetic history (Cullis, 1904; Sibley, 1980). The experimental results presented below are consistent with the interpretation that the dolomitized coralline algal fragment in thin section 1 was LMC at the time of dolomitization. Thin section #1: Partially dolomitized packstone (Pliocene) from Curacao. Coralline algae (lower right) has been selectively dolomitized while the other fossils have been converted to LMC. Dolomite and calcite cement partially fill pores (arrow). EXPERIMENTAL PROCEDURE Experiments consisted of hydrothermally altering six different kinds of carbonate fossils (Table 1). These fossils were composed of HMC, LMC, or ARA and were classified as either microcrystalline or cryptocrystalline. Skeletal materials used in this study were: coral- line algae, echinoids, forams, pelecypods, gastrOpods, and corals. Coralline algae and echinoids were dolomitized from their original HMC mineralogy and after hydrothermal alteration to LMC. All other fossils were dolomitized from their original mineralogies. Fossils were prepared for experimentation in the following manner. First, fossils were broken into pieces ranging from .02-.07 grams and sonically rinsed to remove fine particles from their surfaces. Fossils were soaked for 15-60 minutes in 5.25% sodium hypochlorite to remove surface organics, rinsed with distilled water, and air dried on filter paper. X-ray diffraction analysis before and after soaking in the sodium hypochlorite solution showed that no mineralogical changes had taken place during removal of the organics. Experiments were run in 6.6 and 18.5 ml stainless steel hydrother- mal bombs with copper gasket seals (Appendix 1) placed in a Lindberg Hevi-duty muffle furnace or a Sybran Thermolyne 2000 furnace at 250°C. Pressure within the bombs was calculated using standard steam tables at 39 atmospheres. Table 1. Composition and grain size classification for skeletal materials. Mole % Fossil Grain size Mineralogy MgCO3 Coralline Algae CRYPTO-X HMC 16.9 Echinoid CRYPTO-X HMC 10.7 Foram CRYPTO-X HMC 13.0 LMC 1. 9-3. 0 Pelecypod MICRO-X LMC l . 4 ARA 0 Gastropod MICRO-X ARA 0 Coral MICRO-X ARA 0 CRY PTO-X = Cryptocrystalline MICRO-X = Microcrystalline Solutions used in the synthesis of dolomite and LMC were prepared using CaC12°2 H20 and MgC12°6H20 Baker reagent grade chemicals to form 2M MgClZ and 2M CaClz solutions. Chemistry of the dolomitizing solution was similar for all experi- ments and was patterned after the work of Rosenberg and Holland (1964). Calculated Cay/Ca2+ + Mg2+ ratios for the total substrate and solution chemistry fell in the range of .70-.76, which is near the dolomite— magnesite boundary if temperature is interpolated to 250°C (Figure 1). This composition was chosen because it is the most Mg2+ rich chemistry within the dolomite stability range. no 4 an ‘ ._ - masseuse o . . a " oownou 2 an . 2 . commie e a :5 sea . sowflow ‘ g . .- 'cALcne ' no . / l a / / aownou 0.6V - ' inf ' 3.; T webffifi {.0 nee/(IC- h any) It! SOLUTION Figure 1. Stability fields for magnesite, dolomite and calcite (after Rosenberg and Holland, 1964). Hydrothermal alteration of HMC coralline algae and echinoids to LMC was accomplished by using the 2 molar CaClz solutions at 250°C. Experiments run in 6.6 ml hydrothermal bombs had .0015-.5600 grams of sample with 4.9-5.2 ml of solution at 250°C for 4.5-398 hours. Bombs were quenched in cold water after removing from the oven. 8 Samples were removed soon after quenching and dried on filter paper or rinsed with acetone. Experiments carried out in the 18.5 ml bomb followed the same procedure as above but contained .74-1.00 grams of substrate and 14.0-14.1 ml of solution. A complete listing of experimental parameters is shown in Table 2. ANALYSIS Samples were analyzed using X—ray diffraction or microprobe to determine mineralogy and were observed in thin section and scanning electron microscope to determine textural qualities. X-ray diffraction was performed on a General Electric X-ray diffractometer using CuK radiation and a nickel filter. The apparatus was equipped with a 1° exit slit and a 0.1° and 0.05° scatter slits. Samples were scanned no less than five times at a rate of 2° 2 0/minute through the major peaks of fluorite, calcite, and dolomite and at least twice through the dolomite ordering peaks. Fluorite was used as an internal standard. Mole % compositions for calcite and dolomite were determined from the following equations: Dolomite (104 peak) 30.970 - 2 0 111019 % C8C03 = + 50 .0323 Calcite (104 peak) 261.59 mole % CaC03 = -930.20 sin (2 0/ 2) NN ea. _.n no-. s“ ”an as. _.a .o._. c. an 2. a.“ 3%. on 38 0.2.. a»_ ma. o.s_ coco._ an Na Na. 9.“ ._mn. Na c~_ ”a. 8.“ ua»~. «— ofi «a. 9n :3. 2 Us: 02: an as. a.» sen~. «n «N as. a.e ~nn~. SN n.an_ as. N.“ n.c~. n. 3.: R. 1“ 32. A 38 oz: 288m «N «A. _.A n-_. an ”an as. _.n o_n_. an an a. a.“ :8. R 38 0.3 mn~ am. a.. scan. an an. ea. 8.“ n_ae. _n ~n aa. 8.“ ~_oe. on w__ ma. m.o ANon. _~ 2. R. a; 83m. 8 053 oz: a.e «A. _.n ~.A_. an o~_ .a. _.A on_~. A“ GN— ca. o..~ “nan. a... «N «A. o.n «MAN. an as «A. o.n ”QNN. RN n.u»_ «a. ~.n ona.. a. :2 2. 1n 3:. .2 38 + 0.2: on»? .o :3: a: + +~8>~8 23E .5 5 «Beam a 9m. 8:68... 23°... +N .EuuoEmfim _mucoEtoaxm .~ 03E. 10 n... 8.. c.“ 8%. 2:8 a... 8.. ca 2.... 1:8 02.. .. 52 9a .A. 9n 3%. a. e: .K. 9.... $9.. :3 “A. as. o.n ne-. «N a 2. «A 3:. m. «N 2. N.“ 8R. ». S. R. NA 82.. .. 0.50 + <5. 88.85 n... 8.. ed 8%. 2:3 n... 8.. o... 2.... 2:8 02.. .. $2 “.02 NA. .2 .Nom. R a... i. 9n 3%. an an E. :6 2.8. R 3.8 i. «A 2%. a “A. as. o.n ne.~. «N «8 «A. N.“ 33. 2 0.50 + 52 .200 n.... .a. ~.n smog. n. 0.... .A. «an 28. 2 0.50 + 02.. n.a~. oo.. «.n n.oo. we 0%.. 8.. NA :8. 2 02.. + 0.2.. R E. ca 28. 3 Na .5 N.“ RS. 9 0.50 + 0.2.. Ema". 28: ms. + +~a0>~a0 2...". .e S «as... a. 9m. 5.83... :98“. +N .AvoafiucoUv .N 030... 11 6.0.50 0:0 60000.53» 600930—00 03:0me m0 «9.3.3:. 0380» :0 :3 3:08.593 35:00 .22. 6000033» 0:0 00»? 0:50.50 «0 «0.3.3:. 0.050... :0 E... 3:06.598 35:00 0.. 60569. 00:00—05 5.? 0030.550 3:25.098 ”05:00 .. 8n N... .d .2... N... an R. o... .08. .0 0.50 .. 0.2.. n... 8.. ed 88. 2:8 A... 8.. ca 8.... 2:8 02.. + 5.... E .A. o... :8. 8 n... i. ex .88 an 2 2. 9n «8.. 8 88. i. N.“ 28. 8 SN 2. «A 88. n. 0.50 .. <5. 08.60.»: 28.. A»: + $5.68 2...... .e 5 0.58 a e... 8.88: .08". €08.80. .~ 0.8.. 12 Foram samples, too small to conveniently analyze by X-ray dif- fraction were prepared in polished section and microprobed for CaC03 and MgC03. S.E.M. analysis was performed on an I.S.I. Super III and an 1.5.1. Super III-A S.E.M.; the Super III-A was equipped with a Kevex X-ray system with a 7000 uX analytical spectrometer. This was used to identify chloride precipitates in several samples. RESULTS Coralline Algae Seven experiments were run on the conversion of HMC coralline algae to dolomite lasting from 4.5 to 187.5 hours (Table 3). All experiments lasting 22 hours or more produced well-ordered dolomite. The experi- ment run for 4.5 hours produced a calcium-rich, poorly ordered dolomite. Thin section #2 shows the unalterd skeleton. It is cryptocrystal- line with no preferred Optical orientation of grains. Micrographs #1 and 2 are high and low magnification shots of this texture seen by S.E.M.; micrograph #1 at 20,000X shows cryptocrystalline (< l um). subhedral, and tightly packed HMC. Micrograph #2 at 2,000X shows the porous nature of the fossil. Dolomite produced from the HMC composition is seen in thin section #3. This particular specimen came from an experiment run 22 hours at 250°C. It is cryptocrystalline like its precursor and has retained a partial imprint of the original, porous texture. Micrographs #3 and 4 are comparison shots taken at the same magnification as those for the HMC coralline algae. At high magnification, crystal size and shape of the dolomite appears similar to that of the HMC, although intercrystal- line porosity has increased during dolomitization. At low magnifica- tion, other dolomite textures are seen. Pores in the upper and lower righthand corners of the shot show dolomite rhombs similar to naturally 13 14 Table 3. X-ray diffraction results for experimentation on coralline algae. Initial composition: HMC with 16.9 mole % MgCOB. Crystal size: cryptocrystalline. Mole % Reaction Hrs. of Exp. End Product CaCO3 Exp. # HMC + DOLO 4.5 P-O-DOLO* 53.6 58 22 DOLO 49.9 35 76 DOLO 48.5 29 96 DOLO 49.3 57 120 DOLO 50.6 1** 126 DOLO 48.4 41*** 187.5 DOLO 50.0 14 LMC -> DOLO 22 DOLO 51.0 55 384 DOLO 50.0 37 398 DOLO 49.8 39 HMC + LMC 52 HMC 89.1 30 116 LMC 96.7 20 116 LMC 96.4 21 139 LMC 96.9 31 283 LMC 97.4 59 * Denotes poorly ordered dolomite as the end product. ** Denotes experimentation on fossil framents which had organic coatings. *** Denotes an experiment run with cora11ine algae-gastropod mixture. 15 Thin section #2: Unaltered coralline algae skeleton composed of HMC. Crystals are cryptocrystalline and show no preferred optical orientation. Thin section #3: Dolomite produced from a natural, HMC coralline algae after 22 hours at 250°C. (Exp. #35). Texture is similar to the precursor. Cryptocrystalline crystals show no preferred Optical orientation. I "U? ‘ - 1. ‘ 5“" eg- *5 ”Jeep... ‘v: 17 Micrograph #1: Unaltered, HMC coralline algae (20,000X). Crystals are less than 1 micron in size, subhedral, and tightly packed. Micrograph #2: Unaltered, l-MC coralline algae (2,000X). Porous nature of the fossil is seen. 19 Micrograph #3: Dolomitized HMC coralline algae (20,000X) from experiment #35. Dolomite is cryptocrystalline, subhedral, and more porous than the original HMC crystals. Micrograph #4: Dolomitized HMC coralline algae (2,000X) from experiment #35. Porous nature of the original skeleton has been preserved during dolomitization. Crystal coarsening is observed. Dolomite cement lines central pore (see arrow). 20 21 dolomitized coralline algae (micrograph #54). Dolomite cement lines the pore in the center of the shot. Overall skeletal structure has been preserved during dolomitization. LMC for the reaction of LMC coralline algae to dolomite was syn- thetically produced from the original HMC composition. Experiments lasted from 52 to 283 hours and produced LMC in all experiments run for 116 hours or more (Table 3). The original 16.9 mole % M9003 composi- tion was altered to 10.9 mole z MgC03 after 52 hours and became LMC with 0 3.5 mole Z M9003 in two experiments run for 116 hours. LMC produced from an experiment run 116 hours is seen in thin section #4. It is cryptocrystalline and has a fabric like that of the HMC coralline algae. Using S.E.M. (micrographs #5 and 6), a slight increase in crystal size is apparent. The conversion of synthetic LMC coralline algae to dolomite took place in three different experiments lasting from 22 to 398 hours (Table 3). All experiments produced well-ordered dolomite. Thin section #5 shows the texture produced from the reaction of synthetic LMC to dolomite. This dolomite resulted after 384 hours of reaction and is Virtually indistinguishable from the dolomite produced in the reaction-of HMC to dolomite. Both are predominantly crypto- crystalline with no preferred orientation of crystals and have retained partial imprints of the original fabric. Crystal size and shape of the dolomite produced from LMC (micrographs #7 and 8) appears somewhat coarser and more euhedral than the dolomite produced from HMC. Overall texture at low magnification is similar. 22 Thin section #4: Cryptocrystalline LMC from an experiment (#21) run 116 hours at 250°C. Texture is like that of the natural, HMC. Thin section #5: Dolomite produced after 384 hours or experimentation. Texture is indistinguishable from that of dolomite produced from an HMC coralline algae. 23 24 Micrograph #5: LMC produced from an HMC coralline algae after 116 hours of experimentation. LMC is cryptocrystalline and subhedral. Intercrystalline porosity has increased during the conversion of HMC to LMC. Micrographs #6: LMC produced from a HMC coralline algae after 116 hours of experimentation (2,000X). Overall texture has been preserved. 25 26 Micrograph #7: Dolomitized LMC coralline algae after 384 hours at 250°C (20,000X). Dolomite is cryptocrystalline and subhedral. It is slightly coarser than the dolomite produced from the HMC composition. Micrograph #8: Dolomitized LMC coralline algae from and experiment run 384 hours (2,000X). Overall structure has been preserved. 27 28 Echinoid Echinoids were dolomitized from their original HMC composition and also after conversion to LMC. Thin section #6 is an unaltered fragment. It is porous, cryptocrystalline, and had a common optical orientation of its crystals causing unit extinction (Bathurst, 1975). S.E.M. view of this texture is seen at 2,ooox and 200x in micrographs #9 and 10. The porous nature of the substrate is best seen at low magnification. Crystal size is so small that it is not visible even at high magnification. Conversion of HMC echinoids to LMC was accomplished in four experi- ments run from 92 to 186 hours (Table 4). All experiments produced LMC with slightly lower mole S MgC03 than experiments run on coralline algae. Original composition of the echinoid was 10.7 mole % MgCO3. In thin section (#7), the LMC echinoid texture after 120 hours of experimentation appears similar to that of the HMC composition. It is cryptocrystalline, has unit extinction, and the same porous texture as the HMC echinoid. S.E.M. view of this is seen in micrographs #11 and 12. At 2,000X, the surface texture appears less smooth than that of its precursor. The tight, interlocking texture of LMC crystals makes crystal definition difficult. At 200x, the HMC and LMC textures look nearly identical. Dolomitization of the HMC echinoid was studied in four different experiments run from 22 to 187.5 hours (Table 4). All experiments which used fossils soaked in sodium hypochlorite solution prior to experimentation produced well-ordered dolomite as the single phase end product. The experiment run with an uncleaned echinoid for 174.5 hours produced well-ordered dolomite and LMC as the end product phases. The 29 Table 4. X-ray diffraction results for experimentation on echinoids. Initial composition: HMC with 10.7 mole % MgC03. Crystal size: cryptocrystalline. Mole % Reaction Hrs. of Exp. End Product CaC03 Exp. # I-IMC + DOLO 22 DOLO 50.0 26 35 DOLO 50.2 52 174.5 DOLO 49.8 7* LMC 97.7 187.5 DOLO 50.1 15 LMC -> DOLO 22 DOLO 50.0 54 395 DOLO 49.2 36 398 DOLO 47.8 40 HMC + LMC 92 LMC 98.3 32 120 LMC 99.0 16 120 LMC 99.0 17 186 LMC 96.6 38 * Denotes experiments run on fossils with organic coatings. 30 Thin section #6: Unaltered, cryptocrystalline echinoid skefleton. Preferred optical orientation of crystals is exhibited by unit extinction. Thin section #7: LMC texture from an experiment (#17) conducted for 120 hours at 250°C. Texture is like that of its HMC precursor with cryptocrystalline crystals making up the porous structure. Preferred orientation of the crystals is exhibited by unit extinction. 31 32 Micrograph #9: Unaltered HMC echinoid (2,000X). Skeleton is composed of a porous network. Crystals are too fine and densely packed to identify. Micrograph #10: Unaltered HMC echinoid (200X). Homogeneous, porous network of the skeleton is seen. 33 34 Micrograph #11: LMC echinoid from an experiment run for 120 hours (2,000X). Surface undulations are seen but actual crystals are not identifable. LMC crystals appear as densely packed as the HMC. Micrograph #12: LMC echinoid after 116 hours of experimentation (200X). Overall texture is preserved during conversion to LMC. 35 1.0 via. -5 r‘. 36 experiments run for 22, 35, and 187.5 hours with cleaned fossils pro- duced well-ordered dolomite. Dolomitization of HMC echinoids produced numerous cryptocrystalline and microcrystalline textures. These were not seen in thin section as they appear similar at low magnification but were well-defined by S.E.M. observation. The thin section texture of the dolomitized HMC echinoid (#8) is cryptocrystalline to very fine microcrystalline and has retained the porous network fabric of its precursor. Mimic replacement of the HMC texture is displayed in the preservation of unit extinction. Zones of dissolution and zones of porosity occlusion were readily observed from dolomitization of this substrate. Dolomite textures observed by S.E.M. for the conversion of HMC echinoids are seen in micrographs #13 through 16. Micrographs #13 and 14 came from an experiment run for 22 hours, and are from the same experiment as thin section #8. Micrographs #15 and 16 are from an experiment run 187.5 hours. At 200x, the texture looks the same throughout and from sample to sample. At higher magnification, the differences are obvious. The texture seen in micrograph #13 at 2,000x shows crystals growing into open pore space. The oriented, euhedral crystals appear to have grown ina zone where porosity occlusion was taking place; this may be_re1ated to a zone of dissolution nearby. Micrograph #15 at 2,000X shows cryptocrystalline, anhedral dolomite which replaced the fossil. Three experiments were run on the dolomitization of LMC echinoid fragments (Table 4). They lasted from 22 to 398 hours. All produced well-ordered dolomite. . 37 Thin section #8: Dolomitized HMC echinoid from experiment #26 after 22 hours of experimentation. Mimic replacement is exhibited by preservation of unit extinction. Crystals are cryptocrystalline to very fine microcrystalline. Thin section #9: Dolomitized LMC echinoid after 395 hours at 250°C. Texture is indistinguishable from that of the dolomitized HMC echinoid. Mimic replacement of crystals was observed. 38 39 Micrograph #13: Dolomitized HMC echinoid from an experiment lasting 22 hours (2,000X). Crystals are from 5 to 10 microns in size, euhedral, and oriented. Micrograph #14: Dolomitized HMC echinoid after 22 hours of experimentation (200X). Original texture is recognizable although growth of crystals into open pores has partially occluded the porous network. " 40 41 Micrograph #15: Dolomitized HMC echinoid from an experiment run for 187.5 hours (200X). Crystals are less than 1 micron in size, anhedral, and coallesce to form an undulating surface. Micrograph #16: Dolomitized HMC echinoid from an experiment lasting 187.5 hours (200X). Overall texture of the echinoids is recognizable and like that seen in micrograph #14. Porosity occlusion occurs (see arrow) closer to the fragment surface. 42 7i" t/P‘... 43 Dolomite produced after 395 hours of experimentation on a LMC echi- noid is seen in thin section #9. It is cryptocrystalline to very fine microcrystalline and porous. Mimic replacement of the dolomite is ex- hibited by unit extinction. S.E.M. view of the dolomite is seen in mi- crographs #17 and 18. At 200x, the dolomite texture appears identical to those produced from the dolomitization of HMC echinoid fragments. At 2,000X, the dolomite texture appears much different than either texture produced from dolomitization of a HMC echinoid. Crystals of the dolomitized echinoid are subhedral, oriented, and coarser crystal- line than the dolomite seen in micrograph #15 but finer than those in micrograph #13. m Experimentation on forams consisted of dolomitizing natural HMC and LMC varieties along with recrystallizing natural LMC forams. Precursor forams were cryptocrystalline in all cases and exhibited radiaxial extinction when observed petrographically. Thin section #10 is a rep- resentative shot of a LMC foram with 1.9 mole % MgCO3. An S.E.M. view of this texture is seen in micrographs #19 through 21. This tex- ture is similar to that of the HMC echinoid in that it is so finely crystalline and tightly packed that crystals cannot be identified even at 20,000X. Lower magnification shots at 2,000X and 200x delineate the porous nature of the substrate. . The texture of the HMC foram is 3999 1" micrographs #22 and 23. It has a texture like the HMC coralline algae (and dolomitized HMC coral- line algae) at 20,000X. Crystals are coarser than those of the LMC 44 Thin section #10: Natural LMC foram which is cryptocrystalline and exhibits radiaxial extinction. Thin section #11: Dolomitized HMC foram after 92 hours of experimenta- tion. Cryptocrystalline dolomite fabric exhibits mimic replacement as observed by its radiaxial extinction. 45 46 Micrograph #17: Dolomitized LMC echinoid after 395 hours of reaction (2,000X). Cryptocrystalline, euhedral, oriented, crystals, 1 to 5 microns in size make up the porous texture. Micrograph #18: Dolomitized LMC echinoid after 395 hours of experi- mentation (200X). Texture appears similar to those formed from the dolomitization of HMC echinoids when observed at this magnification. 47 48 Micrograph #19: Unaltered LMC foram at 20,000X. Crystals are too fine to identify even at high magnification. Micrograph #20: Unaltered LMC foram at 2,000X. Porous nature of the skeletal material is observed. 49 50 Micrograph #21: Unal tered LMC foram at 200x. Homogeneous nature and pore distribution is seen. 51 Micrograph #22: Unaltered HMC foram at 20,000X. Cryptocrystalline crystals are anhedral and form a porous texture. Micrograph #23: Unaltered HMC foram at 2,000X (right) and 200x (left). Porous skeletal structure is seen at lower magnification. 52 53 foram but still cryptocrystalline. Crystals are rounded and have more intercrystalline porosity between indivichal crystals. At low magnifi- cations of 2,000X and 200x, the porous nature of the substrate is ob- served from a different perspective. Dolomitization of HMC forams was accomplished in two experiments run for 92 hours, both of which produced dolomite (Table 5). Ordering of the dolomite wasnot studied. Dolomite producederom a HMC foram is seen in thin section #11. It is cryptocrystalline like its precursor and has undergone mimic replacement. Micrographs #24 and 25 show the corresponding S.E.M. ,..textures at 2,000x and 200x. Replacement crystals are coarser than the original HMC and subhedral. Pore-filling crystals are euhedral. At 200x; the gross structure of the central portion of the fossil appeared to have been destroyed during dolomitization as skeletal perforations were filled with dolomite. ”:Conversion of natural LMC forams to dolomite was studied in two experiments lasting 141.5 hours (Table 5). Thin section #12 shows a dolomitized LMC foram fragment. It ap- pears identical to its precursor seen in thin section #10. Both are cryptocrystalline and exhibit radiaxial extinction. S.E.M. view of the dolomite is seen in micrographs #26 and 27. Dolomite crystals are eu- hedral and much coarser than the original LMC. At low magnification of 200x, the aaéiiai loss of skeletal structure from crystal coarsening during dolomitiiation and precipitation of fibrous crystals is seen. The recrystallization of LMC forams was studied in two experiments lasting 129.5 hours. An original LMC composition of 3.0 mole %.MgCO3 was recrystallized to a composition with approximately 1 mole % MgCO3. "‘ v a ..r ‘1 \- o-.. -- _ '. up .~u._~ _.‘. '9" .‘ ~~ \ 9 .‘ s-..‘-“-‘ a I. . ' 'u‘..\. ' ‘ v I . a -..— .- - n .— ¢ . e -u. 54 Table 5. Microprobe results for experimentation on forams. Initial compositions: HMC with 13 mole % MgCO3; LMC with 1.9 mole % MgCOB; LMC with 3.0 mole % MgCOB. Crystal size: cryptocrystalIine. Reaction Hrs. of Exp. End Product CaCO3 MgCO3 Exp. # HMC -> DOLO 92 . DOLO 51.1 48.9 47 92 DOLO 52.8 47.3 48 LMC" -> DOLO 141.5 DOLO 51.0 49.0 42 141.5 DOLO 51.1 49.0 43 LMC“: + LMC 129.5 LMC 99.3 0.7 45 129.5 LMC 98.9 1.2 46 * LMC for the reaction of LMC -> DOLO was originally composed of 1.9 mole % MgCO . N LMC for the rgaction of LMC + LMC was originally composed of 3.0 mole % M3003. j I 55 Micrograph #24: Dolomite produced form a dolomitized HMC foram after 92 hours at 250°C (2,000X). Cryptocrystalline, subhedral crystals make up the replacement texture while coarser, euhedral crystals make up the cement (see arrow). Micrograph #25: Dolomitized HMC foram after 92 hours of reaction (200X). Small pores in the central portion of the skeleton have been occluded. General texture has been preserved. 56 57 Thin section #12: Dolomitized LMC foram from an experiment run 141.5 hours. It appears identical to its precursor (thin section #10) and is cryptocrystalline and undergoes radiaxial extinction. Thin section #13: Recrystallized LMC foram. Cryptocrystalline crystals undergo radiaxial extinction. 58 59 Micrograph #26: Dolomitized LMC foram from an experiment lasting 141.5 hours (2,000X). Dolomite crystals are euhedral and much coarser grained than the original LMC texture. Micrograph #27: Dolomitized LMC foram after 141.5 hours of reaction (200X). Overall texture has been preserved during dolomitization. 60 61 Micrograph #28: Recrystallized LMC foram at 2,000X (from an experiment run 129.5 hours). LMC replacement crystals are less than 1 micron in size and anhedral. Cement crystals are 20 microns in size and euhedral. Micrograph #29: Recrystallized LMC foram after 129.5 hours of reaction. Overall texture is preserved during recrystallization. 62 63 Coral Experimentation with corals consisted of dolomitizing natural aragonitic, microcrystalline samples. Most of the dolomite replaced a LMC phase, so the conversion of aragonite to LMC was also studied. An aragonitic coral is composed of rows of spherulites (oriented vertically in the picture) separated from one another by masses of cryptocrystalline aragonite (thin sections #14 and 15). S.E.M. view of the undolomitized coraltis seen in micrographs #30 and 3] at 1760X and 200x. Micrograph #30 shows a spherulite surrounded byna tightly packed mass of aragonite which appears cryptocrystalline. At low magnifica- tion, the massive area appears to have fibrous crystals in it, although the tight packing makes crystal definition impossible. Porosity of the massive zone is delineated by perforations throughout. Dolomitization of aragontic coral fragments was studied in six experiments lasting from 11.5 to 326.5 hours (Table 6). Experiments produced dolomite and calcite as end product phases, although X-ray diffraction analysis shows dolomite as the sole and product in experi- ments lasting 304.5 hours or more. Dolomite in all experiments was well-ordered. . Thin section #16 was taken from an experiment lasting 304.5 hours. The fragment was composed primarily of LMC with a rim of dolomite. Dolomite at the very rim of the sample is cryptocrystalline to very fine microcrystalline._ Crystals further inward are fine microcrystal- line, anhedral, and have undulose extinction. Dolomite textures seen in S.E.M. micrographs #32 and 33 show the tightly packed nature of the end product. Crystal sizes and shapes could not be identified by S.E.M. observation. .a- 64 Table 6. x-ray diffraction results for experimentation on corals. Initial composition: aragonite. Crystal Size: Microcrystalline. Mole % Reaction I-k's. of Exp. End Product CaCO3 Exp. # ARA -> DOLO 11.5 001.0 53.6 34 LMC 95.5 34 001.0 50.7 27 LMC 98.9 175 DOLO 49.6 23 LMC 98.5 209 DOLO 50.1 12 LMC 99.7 304.5 DOLO 49.6 24 LMC** —-- 326.5 DOLO 49.1 53 ARA + LMC 11.5 LMC 99.6 56* 11.5 LMC 99.1 60* * Denotes experiments run with a mixture of aragonitic fossils. ** X-ray analysis identified dolomite as the sole phase. Staining of thin sections showed that some fragments had both LMC and dolomite present. 65 Thin section #14: Unaltered aragonitic coral. Very fine grained needles compose spherulites (oriented vertically near arrow). Cryptocrystalline masses separate sucessive spherulites. Thin section #15: Unaltered aragonitic coral showing a cross section view through spherulites (see arrow at edge). Zones between rows of spherulites are composed of cryptocrystalline and microcrystalline aragonite. 66 67 Micrograph #30: Unaltered aragonitic coral at 1,76OX. Aragonite needles line the pore in the central portion of the photo. The predominant texture is massive and cryptocrystalline. Micrograph #31: Unaltered aragonitic coral at 200x. It appears massive and cryptocrystalline with a system of fine pores. 68 69 Thin section #16: Dolomite and LMC (stained red) from an experiment run 304.5 hours in a dolomitizing solution (Exp. #24). Two different dolomite textures were observed. Rim dolomite (at arrow) is crypto- crystalline to very fine microcrystalline,;with no visible extinction character. Crystals further inward are anhedral and undulose in nature. Thin section #17: LMC texture produced from an aragonitic coral after 11.5 hours at 250°C in a CaClz solution. Crystals are mncrocrystal- line, subhedral and tightgy packed. 7O 71 Micrograph #32: Dolomite texture produced from an aragonitic coral after 304.5 hours of experimentation (2,000X). Dolomite is very fine microcrystalline to cryptocrystalline and massive. Micrograph #33: Dolomite texture produced from an aragonitic coral (200X). Overall texture is massive. 72 I. I 01' .0 . .1 : I < h. .- . , L. .. . r. . .J ~9v ~ r... . a. . O. u. 7! Ch . M.) I. u I .u n.0,... «7.. u ., . .. .. n I 1 r1: .... . ...r r we :1: , . . . .- . 0.... ,.. L. . .. Y. «a. . . 73 LMC was produced from two experiments run for 11.5 hours on arago- nitic coral fragments. Both experiments produced 100% LMC (Table 6). Thin section #17 is the texture produced from the reaction of ara- gonite to LMC in corals. The end product is a tightly packed fabric of fine to medium microcrystalline calcite. Crystals are undulose and often showed curved twins. Micrograph #34 at 2,000X shows the texture at the boundary of 3 LMC crystals. . ' Crystals appear rough with angular edges. At 200x, the tight packing of the crystals is seen. Some crystal boundaries gre‘définable because of their straight edges. The predominant texture appears massive. Gastropod . Dolomitization of an aragonitic, microcrystalline gastropod was studied. As with the coral, thin rims of dolomite formed while the major portion of the fossil was converted to LMC. Later dolomitization of the LMC produced the predominant dolomite texture. Gastropods (thin section #18) are composed of mdcrocrystalline aragonite fibers making up a cross-lamellar structure. Alternating lamellae are in optical continuity and simultaneously undergo extinc- tion. the tightly packed nature of this substrate is best seen by S.E.M. (micrographs #36 and 37). At 2,000X, the fabric making up a single lamellae appears to have little porositg due to the crystal packing. At 200x, the tight packing of sucessiye 1amellae is seen. Conversion of aragonitic gastropod to LMC was studied in two ex- periments lasting 11.5 hours (Table 7). Each produced LMC as an end product, although one also had residual aragonite. .'1 . .~ ‘ .— s- a s .-» - OI- .. e. .o - u ‘ ' . . I . ta . ' '. . : . ' _ . «in ‘ ...\w~o-o--w~rfl~f'o “" IN. ‘. " .‘. .1" . K. . . 1 . . . “' ' _. ~.... ~9- . oh" "" /-. ‘4 t J a > . a I - ‘1 I) ' . ' .1 ‘ " " - r I W . r '0 . .d D . . -. e r . , \ . 5 .H I e a ‘ J ‘. r' " r \ i. ‘ - . a n .1 , ‘. .- u ' ,_....., . ._ u v... ,.... ...-‘ . 4 . 'F " “- r - s -- . . .. .. ‘ “rem-z“: -..- «I .... r4 ' " moua 0- " " I V .l " . " .....- ,awcn" _ “ ' cu-.." “ "' - . u -.- ‘ "1 o. .. _ -m- .74 Table 7. X-ray diffraction results for experimentation on gastropods. Initial composition: aragonite. Crystal size: microcrystalline. Mole 96 Reaction Hrs. of Exp. End Product CaCO3 Exp. # ARA + 001.0 ' 23. TRACE__DOLO —_ I8 ' ”LMC... . ’ 98.8 "23 001.0 49.5 19 _ - LMC 96.9 126 001.0 50.7 41* LMC 99.8 169 001.0 49.6 11 LMC 99.2 175 1301.0 49.9 22 LMC 99.1 343 001.0 49.3 49 LMC 99.2 ARA + LMC 11.5 LMC 99.9 56* TRACE ARA 11.5 LMC 97.5 60* * Denotes experiments run with a "mixture of skeletal fragments. 75 Micrograph #34: LMC produced from an aragonitic coral after 11.5 hours of reaction at 250°C (2,000X). Resulting spar is medium crystalline and anhedral. Micrograph #35: LMC from an aragonitic coral after 11.5 hours of reaction (200X). Texture appears massive. 76 77 Thin section #18: Unaltered aragonitic gastropod composed of very fine microcrystalline fibers in a tightly packed cross-lamellar structure. Alternating lamellae are in optical continuity and simultaneously undergo extinction. Thin section #19: Aragonitic gastrOpod partially converted to LMC after 11.5 hours at 250°C. Grey zone at top of photo (see arrow) is believed to be aragonite because of the alternating extinction pattern of alternating lamellae. Brown zone in lower half of photo is of very fine microcrystalline LMC. LMC cement lines cracks and forms on the sample surface. 78 nil :1. e 1. u. . 11.9.4 .rwrifiék “a. - strum... in . 79 Micrograph #36: Unaltered aragonitic gastrOpod at 2,000X. Tight interlocking fibers compose lamellae of the cross-lamellar structure. Micrograph #37: Unaltered aragonitic gastrOpod at 200x shows the arrangment of plates in the cross-lamellar structure and the densely packed nature of the skeleton. 80 "L1 q."- 3 I no . a, fin. ..._V ' H II J A 0 ~ 0 ‘u a 4'. .2 r c b s . - o . . .Q'ew . s . I .il . l. . ‘u ... 1... q . 1 . . u. . .0. a J gun—I. ... I . .3 . . a . 4a.... . I”... f 2» . .. v I. . 4- ml. .00 1* 1. 9V: ‘3’: a. a I r. .. .7... . l- 81 The texture produced from the alteration of an aragonitic gastropod to LMC is seen in thin section #19. The brown portion of the fossil in the lower 2/3 of the picture is of a microcrystalline LMC. The upper 1/3 seen in grey has retained the characteristic alternating extinction pattern of aragonite and is believed to be aragonite which was not converted to LMC after 11.5 hours at 250°C. white crystals forming at the rim and through cracks in the samplefiare of LMC cement growing into Open space. Skeletal structure of the lamellaerwas preserved during alteration to LMC. The texture of the LMC is best seen by S.E.M. (micrographs #38 and 39). At 2,000X, subhedral Crystals of very fine crystalline LMC are seen. At 200x, these crystals are on the left 2/3 of the picture. preservation of the cross lamellar structure is apparent. Crystals in the upper right portion of the picture are believed to be aragonite crystals which were not converted to LMC. Six experiments on the dolomitization of aragonitic gastrOpod were studied ranging from 23 to 343 hours. All experiments produced both dolomite and LMC as end product phases. one experiment, run for 23 hours, produced only a trace amount of dolomitefiTable 7). Thin section #20 is from a dolomitized gastropod taken from an experiment lasting 343 299553. The dolomite appears cryptocrystalline with zones of anhedral, undulose, very fihe mflcrocrystalline crystals of dolomite'and LMC. The gross texture of the original cross lamellar texture has been preserved from the conversion of aragonite to LMC and dolomite. S.E.M. view of the dolomite is seen in microgrpahs #40 and 41. At 2,000X, dolomite cement crystals growing at the crystal inter- face appear euhedral and much coarser in comparison with the interior 82 Micrograph #38: LMC texture of a converted gastropod (2,000X). Very fine crystalline to cryptocrystalline, anhedral crystals make up the tightly packed structure. Micrograph #39: LMC and aragonite (2) from a gastropod after 11.5 hours of reaction. Texture to left is of anhedral, LMC crystals. The fibrous nature of the texture on the right (see arrows) may be aragonite which was not converted to LMC. Relicts of the original cross-lamellar structure are recognizable. 83 84 Thin section #20: Dolomitized gastropod after 343 hours of experi— mentation. Crystals are cryptocrystalline to very fine microcrystal- line. Very fine crystals are anhedral, undulose and composed of dolomite or LMC (when stained red). 85 Micrograph #40: Dolomitized gastropod from an experiment lasting 343 hours (2,000X). This shot is of euhedral cement crystals near the rim growing into open pore space. Micrograph #41: Dolomitized gastropod at 200x. Texture appears massive and similar to the dolomitized coral texture. 86 87 dolomite texture which is seen at 200x. Tight packing of the interior dolomite makes textural description difficult. Pelecypod Microcrystalline pelecypods were dolomitized from natural aragonite and LMC compositions. Aragonite was also converted to LMC for the same reason cited for gastropods and corals. The reaction of mncrocrystal- line LMC to dolomite was studied to help determine if the formation of dolomite from aragonite was proceeded by a 100% LMC phase. The natural LMC pelecypod was finer microcrystalline than the synthetic LMC's from originally aragonitic fossils; for this reason, it was believed that the natural LMC pelecypod would dolomitize more readily than the arago- nitic fossils if the aragonite was converted to a coarser LMC phase prior to dolomitization. Thin section #21 is of an aragonitic pelecypod. It is composed of a cross lamellar structure similar to that of the gasropod. Thin section #22 is a shot of the pelecypod from a different angle. S.E.M. view of an undolomitized pelecypod is seen in micrographs #42 and 43. Aragonite fibers are fine but slightly coarser than those of the gastropod; intercrystalline porosity is greatly increased over the gastropod. I Dolomitization of an aragonitic pelecypod was studied in five experiments lasting from 11.5 to 247 hours,(Table.8). The end product in all experiments was dolomite and calcite.w One-experiment, lasting 209 hours, produced a sample with 100% dolomite; other specimens in the experiment produced dolomite and calcite. 88 Table 8. X-ray diffraction results for experimentation on pelecypods. Initial compositions: aragonite and LMC with 1.4 mole % MgCO . Crystal size: microcrystalline. Mole % Reaction I-Irs. of Exp. End Hoduct CaCO3 Exp. # ARA + DOLO 11.5 TRACE DOLO --- 33 LMC 95.9 23 DOLO 53.9 28 LMC 99.1 183.5 DOLO 49.8 25 LMC 96.0 209 DOLO 50.9 13 247 DOLO 49.0 50 LMC 97.2 ARA + LMC 11.5 LMC 99.1 56* 11.5 LMC 98.8 60* TRACE ARA LMC + DOLO 320 P-O-DOLO** 60.1 61 LMC 98.8 320 P-O-DOL0** 60.5 62 LMC 98.1 * Designates experiments run with mixtures of aragonitic fossils. ** Designates poorly ordered dolomite as an end product phase. 89 Thin section #21: Unaltered aragonitic pelecypod exhibiting cross- lamellar structure. Fibers are very fine microcrystalline. Thin section #22: Unaltered aragonitic pelecypod from another angle. 9O 91 Micrograph #42: Unaltered aragonitic pelecypod at 2,000X. Fibers appear coarser than the unaltered gastropod. Porosity of the pelecypod is greater than that of the gastropod. Micrograph #43: Unaltered aragonitic pelecypod at 200x. Cross lamellar structure and pore distribution are well defined at this magnification. 92 93 The texture produced from dolomitization of an aragonitic pelecypod is seen in thin section #23. The crystals stained red are of coarse LMC from the sample interior which resisted dolomitization after 247 hours of reaction. The grey crystals along the rim are dolomite. Dolomite crystals grade from a fine, undulose, xenotopic texture at the rim to medium sized, elongate crystals oriented approximately perpen- dicular to the surface. Micrographs #44 and 45 show the contact between LMC and dolomite. The dolomite crystal size and shape is not identifable using S.E.M. LMC crystals are coarse and euhedral. Thin section #24 is another view of a LMC-dolomite contact. The crystal size and shape of both the dolomiteiand LMC resemble the arago- nite texture seen in thin section #22. .. LMC was produced from aragonitic pelecypod fragments in two experi- ments lasting 11.5 hours (Table 8). One experiment produced both LMC and aragonite. The other produced LMC as the sole phase (Table 8). Thin section #25 is from the experiment which produced aragonite and LMC. The brown fabric on the right side of the plate is of the very fine grained aragonite which was undergoing conversion to the coarse grained, euhedral LMC. LMC‘is not undulose but frequently has curved twins. Micrographs #46 and 47 show the LMC texture at 2,000x and 200x. At 2,000X, the uneven surface texture is reminiscent of the original aragonite fibers. This is also obvious at 200x where skeletal pores also appear preserved. The coarse, euhedral nature of the LMC grains is also seen at 200x. Dolomitization of LMC pelecypods fragments was studied in two experiments lasting 320 hours (Table 8). Both experiments produced calcium-rich, poorly ordered dolomite and a LMC phase. 94 Thin section #23: Dolomite and LMC from a dolomitization experiment on an aragonitic pelecypod (Exp. #50) after 247 hours at 250°C. Dolomite crystals grade from fine to medium microcrystalline from the fossil surface inward while coarse microcrystalline LMC comprises the skeleton's interior. Thin section #24: Dolomite and LMC (stained red) from the same experiment as thin section #23. Very fine crystals have a similar shape and distribution pattern as those seen in thin section #22 of the unaltered aragonite. 95 96 Micrograph #44: Contact between dolomite (upper portion) and LMC (lower portion) in dolomitization experiment on an aragonitic pelecypod (2000X). Both crystals are too coarse to identify at this magnification. Micrograph #45: Dolomite - LMC contact at 200x from a dolomitization experiment on an aragonitic pelecypod. Arrows point toward the contact, with densely packed dolomite crystals in the upper right corner. LMC crystals are euhedral, coarse, and also densely packed. I . § 1\ ' | “ \ \\ ‘5 '97 98 Thin section #25: Aragonitic pelecypod recrystallized to form LMC after 11.5 hours in a CaClz solution at 250°C. Fibrous crystals in the lower right corner are of aragonite. Coarse grained, euhedral LMC is seen in the upper right. Arrows point to LMC crystals with curved twins. 99 Micrograph #46: LMC produced from an aragonitic pelecypod after 11.5 hours of reaction (2000X). Crystal surface is uneven and appears similar to the surface texture of the original aragonitic fibers. Micrograph #47: LMC from an aragonitic pelecypod (200X). Coarse, euhedral crystals form a tighlty packed structure. Pores from the original aragonitic texture have been preserved during conversion to LMC O 100 101 The original LMC texture (thin section #26) is composed of short, very small, foliated fibers with a vesicular texture. Micrographs #48 and 49 show both LMC textures at 2,000X and 200x. In both cases, a tightly packed foliated texture of unrecognizable crystal size makes up the upper portion of the micrograph while a porous, vesicular texture makes up the lower. Dolomitization of the LMC pelecypod produced the texture seen in thin section #27. Calcium-rich, poorly oeae‘ieafi‘momt. from this experiment produced a cryptocrystalline to very fine mncrocrystalline, xenotopic dolomite similar to the texture produced from the dolomitiza- tion of an aragonitic gastropod or the rim dolomite texture of the coral. Brownish colored, fine crystalline zones did not stain from alizarine red and are believed to be of the same composition as the fine grained, poorly ordered dolomite. LMC is seen as the coarser grained area in the lower left-hand corner. S.E.M. view of the dolomite and calcite phases are seen in micrographs #50 and 51. At 2,000X, the dolomite phase is seen as fine crystalline, coalescing rhombs which appear to have a common orientation and massive zones of indeterminable crystal size. At 200x, the tightly packed, foliated region appears preserved, perhaps composedjaf LMC, while the porous, vesicular zone appears to have been replaced by the calcium-rich dolomite phase described above. 102 Thin section #26: Unaltered LMC pelecypod conposed of short, very fine, densely packed fibers. Thi n' section #27: Calcium-rich, poorly ordered dolomite and LMC from a LMC pelecypod after 320 hours of experimentation. Fine, undulose crystals in the lower left (near arrow) are LMC. Very fine micro- crystalline to cryptocrystalline region to the right is of poorly ordered, calcium-rich dolomite. 103 .. i I 14.11.! ‘u‘vflbé I‘lw 104 Micrograph #48: Unaltered LMC pelecypod at 2,000X. Tightly packed, foliated structure (in upper portion of photo near arrow) is made up of crystals of indeterminable size. Vesicular structure (lower portion of photo) is porous and very fine crystalline. Micrograph #49: Unaltered LMC pelecypod at 200x. Contrast between the porosity of the vesicular and foliated structures are obvious at low magnififiation (arrows point toward the foliated structure at the contact . 105 106 Micrograph #50: Calcium-rich, poorly ordered dolomite from a LMC pelecypod. Replacement of the vesicular structure produced very fine crystalline, coallescing rhombs which appear to have a common orientation. Massive zones of the "dolomite" were also observed. Micrograph #51: Calcium-rich, poorly ordered dolomite and LMC from experimentation on a LMC pelecypod (200X). Foliated structure (upper left near arrow) appears preserved and may be composed of LMC. Vesicular structure in lower portion of photo is replaced by oriented rhombs of the "dolomite". 107 '2! ”I I", 3 DISCUSSION Dolomitization of Cryptocrystalline Substrates Dolomitization of cryptocrystalline fossils was accomplished in 19 experiments on HMC and LMC substrates. Experimentation on coralline algae and echinoids produced well-ordered dolomnte in all experiments run for 22 hours or more; based on these experiments, LMC was dolomit- ized as readily as MC in cryptocrystalline substrates. Similar textures were produced from the dolomitization of HMC and LMC compositions of each cryptocrystalline fossil studied. .In thin section and at low magnification using the S.E.M., textures appeared virtually indistinguishable. At higher magnifications, variability of crystal sizes and shapes within a sample and from sample to sample were more pronounced. Hydrothermal dolomitization of both HMC and LMC compositions of echinoids and forams resulted in mimic replacement of the original texture. This shows that optical orientation of the original crystals was not destroyed in the conversion of HMC to LMC in the echinoids, or HMC and LMC to dolomite in echinoidsGand forams. Comparison of dolomite crystal size between the cryptocrystalline substrates indicates a relationship between crystal size and orienta- tion. Dolomite produced from the echinoids and forams was consistently coarser than dolomite produced from coralline algae. It is hypothesized that the parallel orientation of crystals in unaltered forams and 108 109 echinoids allows for coarser crystal growth while the random grain orientation in coralline algae inhibits growth. Dolomitization of Microcrystalline Substrates Dolomitization of microcrystalline aragonite fossils was much slow- er and more complicated than that of cryptocrystalline substrates. Aragonite was unstable at high temperature and converted readily to dolomite if in the presence of sufficient Mg2+ ions or to LMC if not (see Table 2). Thin rims of dolomite formed at the substrate- dolomitizing solution contact while the major portion of the fossil was converted to LMC. The predomdnant dolomite teXture was formed from the conversion of LMC to dolomite with nucleatidfi taking place on the dolomite rim. Variables such as porosity, permeability, surface area: volume ratio, the rate of reaction of aragonite to LMC, and the pres- ence of numerous aragonite and LMC textures within a sample complicated the study. There is no simple correlation between crystal size and mineralogy of the precursor with the rate of dolomitization in arago- nite substrates. Complete dolomitization of an aragonite fossil was not accomplished in any experiment in this study. X-ray diffraction analysis of small fragments (with large surface area: volume ratios) produced dolomite as the single end product phase but larger fragments (with smaller surface area: volume ratios) produced LMC and dolomite from the same experiment. The identification of dolomite produced from aragonite and LMC compositions was most easily accomplished in corals and pelecypods. Thin section #16 from the coral is the best example of this. Rim 11O dolomite produced from the precursor cryptocrystalline to very fine crystalline aragonite is also cryptocrystalline with no preferred crystallographic orientation; it formed within 11.5 hours of reaction (as X-ray diffraction analysis showed that dolomite and LMC were the only phases after that period of time). Later dolomitization of the homogeneous, fine-medium crystalline, subhedral LMC produced the fine crystalline, anhedral, undulose dolomite crystals adjacent to the cryptocrystalline rim. Thin section #23 of a pelecypod also shows two dolomite textures. The fine to very fine crystalline dolomite at the rim is the texture produced from direct dolomitization of the aragbnitic substrate. The medium sized, bladed grains further inward form the second dolomite texture which was produced from the coarse grained, euhedral, LMC spar. Contact between the two dolomite textures is not as pronounced as in the coral due to the cloudy nature of the dolomite produced from the pelecypod. Comparison of the dolomite rim thickness between the coral and pelecypod indicates that the amount of dolomite formed directly from aragonite is greater in the peleoypod. This means that the rate of dolomitization in the coarser crystalline pelecypod may be faster than in the finer crystalline coral. Variables in porosity (micrograph 42). Ca2+/Ca2+ + Mg2+ ratio, or sample proximity to dolomitizing solution may account for this difference. Dolomitization of the aragonite gastropod produced a single dolomite texture. The very fine grained, densely packed, aragonite needles produced a cryptocrystalline dolomite rim and a very fine crystalline LMC (thin section #19). The LMC texture in thin section 111 appeared very similar to that of the precursor aragonite (thin section #18). Later dolomitization of the LMC produced a dolomite texture indistinguishable from that produced from the direct dolomitization of the precursor aragonite (thin section #19). A general preservation of the gross skeletal structure was observed from the original aragonite to the resulting LMC and dolomite compositions. The fine crystal size of all three minerals is believed to account for this phenomenon. The dolomitization of a LMC pelecypod for 320 hours resulted in a poorly ordered, calcium-rich dolomite and a LMC phase. Experiments run for similar time periods on aragonitic fossils (305 and 343 hours for corals and gastropods) produced well ordered dolomite and LMC. This evidence indirectly supports the hypothesis that dolomite forms directly from aragonite in experiments on aragonitic fossils. The LMC pelecypod was finer crystalline than any of the synthetic LMC's, and therefore should have been more susceptible to dolomitization than a 100% LMC of a coarser crystal size. Because the LMC pelecypod resisted dolomitization, it is reasonable that the dolomite produced from the synthetic LMC nucleated on a pre—existing dolomite formed from the aragonite precursor. Comparison of Synthetic and Natural Dolomites Comparison of naturally dolomitized coralline algae from an origi- nal HMC composition was made with synthetic equivalents. The naturally dolomitized specimens were formed under completely different conditions (i.e. pressure, temperature, solution chemistry, etc.) than those in the lab, yet distinct similarities were observed. 112 Micrographs #54 and 55 are comparison shots of dolomitized HMC coralline algae. Micrograph #52 at 17,000X is a naturally produced dolomite with a cryptocrystalline, rhombic texture. It appears very similar to micrograph #53 (15,000X) which is a synthetic dolomite pro- duced from an experiment lasting 126 hours. Packing, crystal size, and shape are all similar between the two specimens, yet the only variables they have in common concerning their formation are the original mfiner- alogy and texture. Micrographs #54 and 55 are comparison shots at 4,000X of natural and synthetic dolomites produced from HMC coralline algae. Micrograph #54 is from a natural dolomite which has retained the original skeletal structure. The dolomite is very fine grained to cryptocrystalline and rhombic. The artificial dolomite came from the experiment run 126 hours and has also retained the original skeletal structure. In this example, the crystal size of the synthetic dolomite is somewhat smaller than the natural specimen which is apposite to that of the previous example. Textures of the two samples are similar. Micrograph #54 also displays a great resemblance to the synthetic dolomite seen in mflcrograph #4 at 2,000X. The artificial dolomite was produced from a HMC to dolomite reaction at 250°C for 22 hours and has approximately the same crystal size, shape, and packing as the natural- ly occurring dolomite rhombs. Another texture produced from a naturally dolomitized coralline algae is seen in micrograph #56 at 2,000X. This specimen has undergone a complete loss of the original texture during dolomitization. Micrograph #56 also at 2,000X, was taken from a LMC to dolomite reac- tion lasting 22 hours; dolomite cement growing on the dolomitized 113 Micrograph #52: Naturally dolomitized HMC coralline algae at 17,000X. Crystals are cryptocrystalline (5-10 microns), euhedral, and form a porous texture. Micrograph #53: Artificially dolomitized HMC coralline algae from an experiment conducted for 126 hours at 250°C (15,000X). Crystals are euhedral, cryptocrystalline and of the same porous nature as the natural dolomite in micrograph #52. 114 115 Micrograph #54: Naturally dolomitized HMC coralline algae at 4,000X. Euhedral rhombs are cryptocrystalline and appear oriented. Original texture of the HMC as been preserved. Micrograph #55: Artifically dolomitized HMC coralline algae from the experiment run 126 hours (4,000X). Crystals are euhedral and cryptocrystalline. Original structure of the coralline algae has been preserved. 116 117 Micrograph #56: Naturally dolomitized HMC (?) coralline algae at 2,000X. This specimen has undergone a complete loss of texture during dolomitization. Micrograph #57: Artifically dolomitized LMC coralline algae from an experiment conducted 22 hours at 250°C (2,000X). This specimen has undergone a complete loss of original texture during dolomitization. Cement has filled the pore space completely masking the original skeletal structure. 118 .5 ikr . l ' I I o ‘ o' c . D . v ‘ f‘h‘ .- h‘ . 4 r .' , ‘ . , i' ‘ .‘no'. - 'Jr ‘3 .\ m. ' ’ . .I .9. ‘1: w - . \. '1 . y, l ‘ ' ’xc": ' . v. Q. l ,t ‘y .. | x. 1 _ . { ‘ . ‘ 0|. ‘. ”-13 "x '1‘ _ l I \ . --.,-'v’ . N ;I~ " .4: "'5" '- "- f '6) I 9 5». :1. I) . '. . . " ’.:'9.1} l: "I ""‘T ’ _ , - . I ' . - I ‘0 ‘ .- . ,1 - ,» - 4 - n O ‘. ‘2“ “.5 " . o ‘ ' " .~ ‘5‘!“ , . . l ' 'v l-‘s': 119 coralline algae has masked the original skeletal structure and produced a texture like that of the natural specimen. These two samples were formed under completely different conditions, yet resulted in the same texture. The only variable in comnon between the substrates was their original crystal size, as the natural specimen is believed to have formed from a HMC composition. Naturally dolomitized echinoid and foram fragments commonly show mimic replacement but they may also resist dolomitization (Sibley, 1982). Mimic replacement may.occur prior to or after conversion of HMC to LMC. The fragments resist dolomitization after conversion to LMC. Therefore, there is only a partial correspondence between the experimental results and naturally dolomitized echinoids and forams. Aragonitic fossils seldom show mimic replacement in nature or in the experiments. Aragonitic fossils subjected to dolomitizing solu- tions in nature generally are either dissolved or replaced by micro- crystalline dolomite. The major difference between natural and hydrothermal dolomitization is that the natural dolomites tend to be coarser crystalline and euhedral whereas the hydrothermal dolomites tend to be finer and anhedral. LMC mollusk fragments commonly resist dolomitization in nature (Sibley, 1982) as they did in our hydrothermal experiments. The similarity between natural and artifical dolomites demonstrates a substrate control on the orientation and frequenoy of dolomite nuclei. The "control" could be a function of substrate reactivity and/or permeability. *For nucleation, the two aspects of reactivity that are important are the solubility of the substrate and the surface energy of the substrate-nuclei. The solubility of the substrate is a 120 function of its crystal size and mineralogy. The experiments rule out the latter being of major importance because LMC coralline algae, echinoids, and forams were dolomitized as readily as the same fossils with HMC mineralogy. Crystal size may effect the reactivity because coarse crystalline LMC oysters reacted to form only small amounts of poorly ordered dolomite. The HMC fossils studied are finer crystalline, more porous and per- meable than the other fossils. Hhen these fossils were converted to LMC, their structure was not significantly changed: they retained their high porosity and permeability. Thus it may be the access to fluids that caused the abundant nucleation sites. The aragonite fos- sils and calcitic oyster formed reaction rims which may represent the limit to which dolomitizing fluids were able to penetrate into the fossil. They could also represent the more complex situation: the reaction rims might be the result of the penetration of dolomitizing fluids causing dolomite to nucleate along with coarsening of LMC in the fossils, which inhibitied the nucleation. Mimic Replacement During_Hydrothermal Dolomitization Mimic replacement of oriented crystals was observed in echinoids and forams composed of HMC or LMC but not in aragonitic corals. As explained previously, control over crystal orientation during dolomit- ization may be related to the mineralogy or crystal size of the precur- sor or to its permeability. Echinoids and forams were cryptocrystal- line, but the coral spherulites were very fine crystalline. If crystal size is the main control over replacement crystal orientation, the finer crystalline echinoids and forams would be more apt to undergo 121 mimic replacement because of their greater surface area: volume ratios, greater solubility, and their abundant nucleation sites. The effect of mfineralogy or perhaps more importantly, the differ- ence in crystal systems between the calcitic minerals (trigonal system) and aragonite (orthorhombic) during the replacement by dolomite (trigonal) is a second consideration. If the change in crystal system has an effect on crystal orientation, the aragonitic coral would be less apt to undergo mimic replacement whereas the calcitic fossils wouldn't be affected. A third consideration in reactivity is permeability. If the great- er permeability of the echinoids and forams is the major control over replacement crystal orientation, they would be expected to be more reactive than the less permeable coral. As only the rims of the coral were dolomitized, the effect of permeability over crystal orientation does not appear to be significant. CONCLUSIONS The main conclusions of this study concerning the effect of precursor crystal size and mflneralogy on resulting dolomite textures and rates of dolomitization are listed in Table 9. These conclusions are as follows: 1) 2) 3) 4) Cryptocrystalline HMC is very susceptible to dolomitization and exhibits mimic replacement in fabrics with oriented crystals. Cryptocrystalline LMC is as susceptible to dolomitization as HMC substrates under the conditions of this experimentation and also undergoes mimic replacement. Microcrystalline LMC resists dolomitization and does not undergo mimic replacement. The susceptibility of microcrystalline aragonite to dolomitiza- tion could not be determined under the experimental con- straints. The reaction of ARA to LMC at high temperature converted most of the substrate to LMC before appreciable amounts of dolomite could form. These results lead to the conclusion that crystal size is more important than mineralogy in determining the nature of dolomite selectivity in HMC and LMC substrates. Further study is needed to delineate the relationship in aragonitic substrates. 122 123 Table 9: Conclusions of Study MINERAL CRYSTAL SIZE SUSCEPT. DOLON MIMIC REPLACE HMC CRYPTO-X VERY HIGH YES LMC CRYPTO-X VERY HIGH YES LMC MICRO-X LOH NO ARAG MICRO-X NOT DETERMINED NO CRYPTO-X = cryptocrystalline MICRO-X - microcrystalline Other conclusions are as follows: 5) 6) Comparison of natural dolomite textures with those produced synthetically in the laboratory at higher P-T conditions and under different chemical constraints, leads to the conclusion that the original texture (i.e. crystal size) is more important in determining the resulting dolomite texture than any other variable. These results can be applied to natural dolomites in the fol- lowing manner. Selective dolomitization of originally HMC fossils (such as shown in Figure l) is probably a result of the original fossil texture and could occur after conversion to LMC. Fresh water diagenesis which changes fossil textures will affect the susceptibility of those fossils to dolomitization. FUTURE WRK Subjects directly related to this study which deserve further investigation are listed as follows: (1) (2) (3) (4) Fossil mixtures of substrates which resist dolomitization and those which are readily dolomitized should be hydrothermally dolomitized to better understand the 003‘ ion exchange between substrates undergoing dissolution-reprecipitation reactions. This will allow a better understanding of whole rock reactions during dolomitization. Hydrothermal dolomitization experiments should be run to bet- ter understand the mechanics of crystal growth and dissolu- tion. Bombs should be sampled at specific intervals to deter- mine if dolomite grains become more rounded (i.e. dissolve at points of greatest surface area) with time after initial dolo- mite formation. The number of dissolution-reprecipitation events should be studied for the reaction of HMC to dolomite. This reaction is specifically interesting because of the number of different dolomite textures produced within a single sample and from sample to sample in coralline algae and echinoids. Echinoids should be studied more thoroughly in hydrothermal alteration experiments. This substrate has a similar surface 124 (5) (6) (7) (8) (9) 125 area: volume ratio no matter how it is fractured and seems quite suitable to experimentation. Microcrystalline substrates which exhibit optical character- istics related to crystal orientation should be studied to determine the replacement mechanics during hydrothermal alteration. The rate of reaction of aragonite to LMC in different sub- strates deserves further investigation to determine the rela- tionship between the rate of reaction, the precursor texture, and the resulting texture. Pelecypods which convert to coarse crystalline, euhedral, LMC should be studied along with those substrates which form finer grained, anhedral, LMC crystals. This type of study would better define the relative importance of porosity and grain size during crystal growth. Comparison of a greater variety of naturally dolomitized fossils should be made with artificially dolomitized equivalents. This is important not only for stressing the dependence of dolomite texture on precursor texture, but also for comparing dolomite textures formed by a local source of 003‘ ions with dolomites formed in an Open system (i.e. with an outside source of 003‘ ions). Recrystallization of both natural and artificially produced well-ordered dolomites should be attempted to determine if recrystallization of a stable mineral phase takes place, and if so, why recrystallization occurs. The importance of grain size and mineralogy during hydrother- mal dolomitization should be quantified. Synthetic aragonitic (10) 126 and calcitic precipitates of similar grain size should be hydrothermally dolomitized under the same P-T and chemical conditions to determine relative dolomitization rates for specific grain sizes and mineralogies without the considera- tion of different porosities. This would be especially important in the study of aragonitic substrates. The rate of dolomitization in substrates which resist dolomitization deserves further study. Experiments run in the presence of dolomite (and protodolomite) seeds could be studied to determine: (a) If the presence of dolomite speeds the reaction rate in the resistive substrate, (b) If the presence of dolomite favors dissolution of the resistive substrate with corresponding cementation cement formation on the dolomite, or (c) if the presence of dolomite has no effect on the reaction rate in the resistive substrate. A study of this nature would allow a better understanding of whole rock reactions during dolomitization. APPENDIX 1 HYDROTHERMAL BOMB DESIGNS 127 para. Figure 1 Figure 2 Figure 1. 18.5 ml capacity Morey-type hydrothermal bomb (Morey, 1953). Figure 2. 6.5 ml stainless steel bomb. APPENDIX 2 EXPERIMENTAL RESULTS 128 EXPERIMENT #: 1 REACTION: HMC t0 Dolomite FOSSIL: Coralline Algae (uncleaned sample) ORIGINAL COMPOSITION: 16.9 111% MgCO3 FINAL COMPOSITION: 50.6 m% CaCO3 SAMPLE in: .2136 gm MOLECULAR HT: 97.42 m/gm SUBSTRATE CHEMISTRY: moles M92+: 0.00037 moles Ca2+: 0.01820 SOLUTION CHEMISTRY: 1.3 m1 M9012 (2M) 3.9 ml CaClz (2M) moles Mng: 0.0026 moles Ca2+: 0.007s SOLUTION RATIO: mCa2+ _. = 0.75 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 120 HRS. 129 EXPERIMENT #: 7 REACTION: HMC to Dolomite FOSSIL: Echinoid (uncleaned sample) ORIGINAL COMPOSITION: 10.7 m%ngCO3 FINAL COMPOSITION: 49.8 m% CaCO3 SAMPLE HT: 0.1361 gm MOLECULAR HT: 98.40 gm/mole SUBSTRATE CHEMISTRY: moles MgZi: 0.00015 moles Ca2+: 0.00124. SOLUTION CHEMISTRY: 1.3 ml MgClz (2M) 3.9 ml CaClz (2m moles Mgzi: 0.0026 moles Ca2+: 0.0078 SOLUTION RATIO: mCa2+ _. = 0.75 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 174.5 HRS. 130 EXPERIMENT #: 11 REACTION: Aragonite to Dolomite FOSSIL: GastrOpOd ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 49.6 m% CaCO3 (DOLO) + 0.8 m%ngCO3 (LMC) SAMPLE HT: 0.2003 90 MOLECULAR HT: 100.09 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.0000 moles Ca2+: 0.0020 SOLUTION CHEMISTRY: 1.7 ml MgCTZ (2M) 3.5 ml CaClz (2M) moles MgZ+z 0.0034 moles Ca2+: 0.0070 SOLUTION RATIO: SOLID + SOLUTION RATIO: mCa2+ 8 0.73 'mCaZ+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 120 HRS. 131 EXPERIMENT #: 12 REACTION: Aragonite to Dolomite FOSSIL: Coral ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 50.1 m% CaCO3 (DOLO) + 0.8 m%.MgCO3 (LMC) SAMPLE in: 0.2101 90 MOLECULAR HT: 100.09 gm/mole SUBSTRATE CHEMISTRY: moles M922: 0.0000 moles Ca2+: 0.0021 SOLUTION CHEMISTRY: 1.7 m1 M9C12 (2M) 3.5 ml CaClz (2M) moles MgZT: 0.0034 moles Ca2+: 0.0070 SOLUTION RATIO: mCa2+ _. 8 0.67 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: mCa2+ 0.73 mCa2+ + mMg2+ - TEMPERATURE: 250°C REACTION TIME: 209 HRS. 132 EXPERIMENT #: 13 REACTION: Aragonite t0 DOIOmTte FOSSIL: Pelecypod ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 50.9 m% CaCO3 (DOLO1 SAMPLE NT: 0.2554 gm MOLECULAR NT: 100.09 gm/moTe SUBSTRATE CHEMISTRY: mOIeS M92+: 0.0000 mOTeS Ca2+: 0.0026 SOLUTION CHEMISTRY: 1.7 m1 M9012 (2M) 3.5 m1 CaCIZ (2M) m01es MgZ+z 0.0034 moTes Ca2+: 0.0070 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 209 HRS. 133 EXPERIMENT #: 14 REACTION: HMC t0 OOTOmite FOSSIL: Cora111ne Algae ORIGINAL COMPOSITION: 16.9 mZTMgCO3 FINAL COMPOSITION: 50.0 mi COCO3 SAMPLE NT: 0.1930 gm MOLECULAR NT: 97.42 gm/moTe SUBSTRATE CHEMISTRY: moTes MgZ+: 0.00033 moles Ca2+: 0.00164 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.7 m1 CaCTZ (2M) 11101 es 1492*: 0.0030 moles Ca2+: 0.0074 SOLUTION RATIO: mCaz+ _ = 0.71 mCa2+ + TnMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 187.5 HRS. 134. EXPERIMENT #: 15 REACTION: HMC tO,DOIOm1te FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 m% MgCO3 FINAL COMPOSITION: 50.1 m% CaCO3 SAMPLE HT: 0.2013 gm MOLECULAR HT: 98.40 gm/mole SUBSTRATE CHEMISTRY: moles Mng: 0.00022 moles Ca2+: 0.00182 SOLUTION CHEMISTRY: 1.5 m1 MgC12 (2M) 3.7 m1 COCTZ (2M) moles MgZ+: 0.0030 moles Ca2+: 0.0074 SOLUTION RATIO: SOLID + SOLUTION RATIO: mCa2+ = 0.74 'MCaZT + mMg2+ TEMPERATURE: 250“C REACTION TIME: 187.5 HRS. 135 EXPERIMENT #: 16 REACTION: HMC t0 LMC FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 m%»MgCO3 FINAL COMPOSITION: 1.0 m% CaCO3 SAMPLE NT: 0.2591 gm MOLECULAR NT: 98.40 gm/mo1e SUBSTRATE CHEMISTRY: mO1es Mgz*: 0.00028 m01es Ca2+: 0.00235 SOLUTION CHEMISTRY: 5.0 m1 COC12 (2M) m01es MgZT: 0.0000 m01es Ca2+: 0.0100 SOLUTION RATIO: MC02+ __ = 1.00 mCa2+ + mM92+ SOLID + SOLUTION RATIO: mCa2+ _f = 0.98 mCaz+ + InMg2+ TEMPERATURE: 250°C REACTION TIME: 120 HRS. 136 EXPERIMENT #: 17 REACTION: HMC to LMC FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 m% MgCO3 FINAL COMPOSITION: 1.0 m% CaCO3 SAMPLE NT: 0.2877 gm MOLECULAR NT: 98.40 gm/mOTe SUBSTRATE CHEMISTRY: m01es MgZT: 0.00031 moTes Ca2+: 0.00260 SOLUTION CHEMISTRY: 5.0 m1 CaC12 (2M) mO1eS MgZI: 0.0000 m01es Ca2+: 0.0100 SOLUTION RATIO: mCa2+ _. = 1.00 ITTCaIZ+ + mMg2+ SOLID + SOLUTION RATIO: mCaz+ TEMPERATURE: 250°C REACTION TIME: 120 HRS. 137 EXPERIMENT #: 18 REACTION: Aragonite to 0010m1te FOSSIL: GastrOpod ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: Trace 0010m1te + 1.8 m% MgCO3 (LMC) SAMPLE NT: 0.3703 gm MOLECULAR NT: 100.09 gm/moTe SUBSTRATE CHEMISTRY: mo1es MgZT: 0.0000 mOTes Ca2+: 0.0037 SOLUTION CHEMISTRY: 1.7 m1 M9012 (2M) 3.5 m1 CaC1z (2M) mO1es MgZ+: 0.0034 m01eS Ca2+: 0.0070 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 23 HRS. 138 EXPERIMENT #: 19 REACTION: Aragonite t0 0010m1te FOSSIL: GastrOpOd ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 49.5 m%1CaCO3 (DOLO) + 3.1 m% M9003 (LMC) SAMPLE NT: 0.3105 gm MOLECULAR NT: 100.09 gm/moTe SUBSTRATE CHEMISTRY: m01es "92+. 0.0000 mO1es Ca2+: 0.0031 SOLUTION CHEMISTRY: 1.7 01 MgC12 (2M) ' 3.5 m1 C3012 (2M) mO1es Mng: 0.0034 mO1es Ca2+: 0.0070 SOLUTION RATIO: mCa2+ _. = 0.67 mCa2+ + 111M97-+ SOLIO + SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 23 HRS. 139 EXPERIMENT #: ZO REACTION: HMC to LMC FOSSIL: Cora11ine A19ae ORIGINAL COMPOSITION: 16.9 mz.MgC03 FINAL COMPOSITION: 3.3 m: MgC03 SAMPLE NT: 0.3626 gm MOLECULAR NT: 97.42 gm/mo1e SUBSTRATE CHEMISTRY: mOTes M92*: 0.00063 mOTes 082+: 0.00309 SOLUTION CHEMISTRY: 4.9 m1 CaC12 (2M) mCTes Mgz+: 0.0000 mO1es Ca2+: 0.0098 SOLUTION RATIO: mCaZ+ MCa2+ + ITIMgz+ a 1.00 SOLID + SOLUTION RATIO: mCa2+ _E = 0.95 TnCa2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 116 HRS. 140 EXPERIMENT #: 21 REACTION: HMC t0 LMC FOSSIL: Cora11ine A1gae ORIGINAL COMPOSITION: 16.9 111% MgCO3 FINAL COMPOSITION: 3.3 m% MgCO3 SAMPLE HT: 0.3027 gm MOLECULAR HT: 97.42 gm/m01e SUBSTRATE CHEMISTRY: m01es M92+: 0.00053 m01es Ca2+: 0.00258 SOLUTION CHEMISTRY: 4.9 m1 CaC12 (2M) m01es "92+. 0.0000 m01es Ca2+: 0.0098 SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 116 HRS. 141 EXPERIMENT #: 22 REACTION: Aragonite to 0010m1te FOSSIL: GastrOpOd ORIGINAL COMPOSITION: COCO3 FINAL COMPOSITION: 49.9 m% COCO3 (DOLO) + 0.9 m1 MgCO3 (LMC) SAMPLE NT: 0.2243 gm MOLECULAR NT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: 11101es Mgz“: 0.0000 m01es CazI: 0.0022 SOLUTION CHEMISTRY: 1.5 m1 M9012 12") 3.4 m1 CaC12 (2M) m01es "92+. 0.0032 m01es 002*: 0.0068 SOLUTION RATIO: mCa2+ 0.58 MCBZT + 1111492+ SOLID + SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 175 HRS. 142 EXPERIMENT #: 23 REACTION: Aragonite t0 0010m1te FOSSIL: C0r61 ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 49.6 m% CaCO3 (DOLO) + 1.5 m%1MgCO3 (LMC1 SAMPLE HT: 0.2143 gm MOLECULAR HT: 100.09 gm/mo1e SUBSTRATE CHEMISTRY: m01es M92*: 0.0000 m01es C82+: 0.0021 SOLUTION CHEMISTRY: 1.6 01 M9C12 (2M) 3.4 m1 COC12 (2M) mO1eS M921: 0.0032 m01es Ca2+: 0.0068 SOLUTION RATIO: mCa2+ __ = 0.58 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: mCa2+ .3 8 0.74 mCa2+ + mMgz+ TEMPERATURE: 250°C REACTION TIME: 175 HRS. 143 EXPERIMENT #: 24 REACTION: Aragonite t0 0010mite FOSSIL: CoraT ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 49.6 m% CaCO3 SAMPLE NT: 0.3443 gm MOLECULAR NT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZT: .0.0000 moles Ca2+: 0.0034 SOLUTION CHEMISTRY: 1.7 m1 MgC12 (2M) 3.2 m1 CaC12 (2M) moTes M92+: 0.0034 m01es Ca2+: 0.0064 SOLUTION RATIO: mCa2+ 0.55 IMCaZT + mMg2+ SOLID + SOLUTION RATIO: mCazT _. = 0.74 111Ca2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 304.5 HRS. 1444 EXPERIMENT #: 25 REACTION: Aragonite t0 0010m1te FOSSIL: Pe1ecypod ORIGINAL COMPOSITION: CaCO3 FINAL COMPOSITION: 49.8 m% CaC03 (DOLO) + 4.0 m% MgCO3 (LMC) SAMPLE HT: 0.3473 gm MOLECULAR HT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es Mgz+: 0.0000 m01es 062*: 0.0035 SOLUTION CHEMISTRY: 1.7 m1 M9C12 (2M) 3.2 m1 CaC12 (2M) m01es MgZT: 0.0034 m01es CaZT: 0.0064 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 183.5 HRS. 145 EXPERIMENT #: 26 REACTION: HMC t0 DOLO FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 m%»MgCO3 FINAL COMPOSITION: 50.0 m% CaC03 SAMPLE NT: 0.2532 gm MOLECULAR NT: 98.40 gm/moTe SUBSTRATE CHEMISTRY: m01es MgZT: 0.00028 m01es Ca2+: 0.00230 SOLUTION CHEMISTRY: 1.5 m1 MgC12 (2H) 3.4 m1 0:012 (2M) m01es Mgz+: 0.0030 mO1es Ca2+: 0.0068 SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 22 HRS. 146 EXPERIMENT #: 27 REACTION: Aragonite t0 0010mite FOSSIL: Cora1 ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 50.7 111% C6003 (00L0) +1.1 m2 M9003 (LMC) SAMPLE HT: 0.2048 gm MOLECULAR HT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es Mgz+: 0.0000 moles CaZ+: 0.0020 SOLUTION CHEMISTRY: 1.6 m1 MgC12 (2M) 3.4 m1 CaC12 (2M) m01es Mgz+: 0.0032 m01es Ca2+: 0.0068 SOLUTION RATIO: NICO2+ s 0.58 ‘Eh32+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C ' REACTION TIME: 34 HRS. 147 EXPERIMENT #: 28 REACTION: Aragonite to 0010m1te FOSSIL: Pe1ecypOd ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 53.9 0% CaC03 (DOLO) + 1.1 m%:MgC03 (LMC) SAMPLE NT: 0.1932 gm MOLECULAR NT: 100.09 gm/moTe SUBSTRATE CHEMISTRY: m01es MgZT: 0.0000 0101 es 002+: 0.0019 SOLUTION CHEMISTRY: 1.6 m1 MgC12 (2M1 3.4 m1 0:012 (2M) m01es MgZ*: 0.0032 m01es C02+: 0.0068 SOLUTION RATIO: mCa2+ = 0.58 111Ca2+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 23 HRS. 148 EXPERIMENT #: 29 REACTION: HMC t0 0010m1te FOSSIL: C0ra111ne A1gae ORIGINAL COMPOSITION: 16.9 m% MgC03 FINAL COMPOSITION: 48.5 m% CaCO3 SAMPLE NT: 0.2288 gm MOLECULAR NT: 97.42 gm/m01e SUBSTRATE CHEMISTRY: moTes Mgz*: 0.00040 m01es 062+: 0.00195 SOLUTION CHEMISTRY:‘ 1.5 m1 MgC12 (2M) 3.5 m1 COC12 (2M) mo1es Mgz+: 0.0030 mO1es Ca2+: 0.0070 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 76 HRS. 149 EXPERIMENT #: 3O REACTION: HMC t0 LMC FOSSIL: C0r611ine A198e ORIGINAL COMPOSITION: 16.9 m%.MgCO3 FINAL COMPOSITION: 10.9 m%.MgC03 SAMPLE NT: 0.4012 gm MOLECULAR NT: 97.42 gm/m01e SUBSTRATE CHEMISTRY: m01es Mgz+: 0.00070 m01es Ca2+: 0.00342 SOLUTION CHEMISTRY: 5.0 m1 CaC12 (2M) m01es Mgz*: 0.0000 m01es CaZ+: 0.0100 SOLUTION RATIO: INCa2+ = 1.00 LMCaZT + NIMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 52 HRS. 150 EXPERIMENT #: 31 REACTION: HMC t0 LMC FOSSIL: Cora1110e A19ae ORIGINAL COMPOSITION: 16.9 m%.MgCO3 FINAL COMPOSITION: 3.1 m% MgCO3 SAMPLE NT: 0.4713 gm MOLECULAR NT: 97.42 gm/m01e SUBSTRATE CHEMISTRY: m01es Mgz*: 0.00082 m01es 002+: 0.00402 SOLUTION CHEMISTRY: 5.0 m1 CaC12 (2M) m01es MgZT: 0.0000 m01es Ca2+: 0.0100 SOLUTION RATIO: mCa2+ — =1.m m002+ + mMg2+ SOLID + SOLUTION RATIO: mCazT TEMPERATURE: 250°C REACTION TIME: 139 HRS. 151 EXPERIMENT #: 32 REACTION: HMC t0 LMC FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 m% MgC03 FINAL COMPOSITION: 1.7 m1 CaCO3 SAMPLE NT: 0.3914 gm MOLECULAR NT: 98.40 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZ+: 0.00043 m01es Ca2+: 0.00355 SOLUTION CHEMISTRY: 5.0 m1 C0012 (2M) m01es Mng: 0.0000 m01es 002+: 0.0100 SOLUTION RATIO: mC02+ __ = 1.00 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 92 HRS. 152 EXPERIMENT #: 33 REACTION: Aragonite t0 0010m1te FOSSIL: Pe1ecypod ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: Trace DOLO + 4.1 m% MgCO3 (LMC) SAMPLE HT: 0.2891 gm MOLECULAR NT: 100.09 gm/moTe SUBSTRATE CHEMISTRY: m01es M921: 0.0000 m01es 002+: 0.0029 SOLUTION CHEMISTRY: 1.7 m1 M9012 (2M) 3.3 m1 CaC12 (2M) m01es Mgz*: 0.0034 m01es Ca2+: 0.0066 SOLUTION RATIO: ITICa2+ TEMPERATURE: 250°C REACTION TIME: 11.5 HRS. 153 EXPERIMENT #: 34 REACTION: Aragonite t0 DO1omite FOSSIL: Cora1 ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 53.6 mz.CaC03 (00L0) + 4.5 m% MgC03 (LMC) SAMPLE HT: 0.3604 gm MOLECULAR NT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZT: 0.0000 m01es CazI: 0.0036 SOLUTION CHEMISTRY: 1.8 m1 M9012 (2") 3.2 m1 CaC12 (2M) m01es Mng: 0.0036 m01es COZT: 0.0064 SOLUTION RATIO: NICO2+ __ c 0.54 mCa2+ + mMng SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 11.5 HRS. 154 EXPERIMENT #: 35 REACTION: HMC t0 00101111 te FOSSIL: CorOTT'Ine A1 gae ORIGINAL COMPOSITION: 16.9 (11% MgCO3 FINAL COMPOSITION: 49.9 111% CaCO3 SAMPLE HT: 0.2533 gm MOLECULAR NT: 97.42 gm/mOTe SUBSTRATE CHEMISTRY: m01es Mgz+: 0.00044 m01es Ca2+: 0.00216 SOLUTION CHEMISTRY: 1.5 01 M9012 (2M) 3.5 1111 06012 (2M) m01es MgZT: 0.0030 m01es Ca2+: 0.0070 SOLUTION RATIO: (1082+ TEMPERATURE: 250°C REACTION TIME: 22 HRS. 155 EXPERIMENT #: 36 REACTION: LMC t0 0010m1te FOSSIL: Echinoid ORIGINAL COMPOSITION: 1.73 m% MgCO3 FINAL COMPOSITION: 49.2 m% CaCO3 SAMPLE NT: 0.2238 gm MOLECULAR NT: 99.81 gm/m01e SUBSTRATE CHEMISTRY: m01es Mgz*: 0.00004 m01es Ca2+: 0.00220 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.5 m1 Cac12 (2M) m01es MgZT: 0.0030 m01es Ca2+: 0.0070 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 395 HRS. 156 EXPERIMENT #: 37 REACTION: LMC to 0010m1te FOSSIL: Cora1line A1gae ORIGINAL COMPOSITION: 3.09 m% MgCO3 FINAL COMPOSITION: 50.0 m% C0003 SAMPLE HT: 0.2648 gm MOLECULAR NT: 99.59 gm/moTe SUBSTRATE CHEMISTRY: m01es MgZT: 0.00008 m01es C02+: 0.00258 SOLUTION CHEMISTRY: 1.5 m1 M9C12 (2M1 3.4 m1 06012 (2M) mOTeS Mng: 0.0032 m01es 002+: 0.0068 SOLUTION RATIO: mCa2+ 0.58 ‘MC02+ + TnMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 384 HRS. 157 EXPERIMENT #: 38 REACTION: HMC t0 LMC FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 mz.MgC03 FINAL COMPOSITION: 3.4 m5 M9C03 SAMPLE NT: 1.0060 gm MOLECULAR NT: 98.40 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZT: 0.00110 m01es Ca2+: 0.00912 SOLUTION CHEMISTRY: 14.0 m1 CaC12 (2M) m01es M92+: 0.0000 m01es CaZ+: 0.0280 SOLUTION RATIO: 111062+ = 1.00 ‘MC02+ + mMg2+ SOLID + SOLUTION RATIO: mCaz+ _. = 0.97 mCa2+ + mMg2+ TEMPERATURE: 250°C - REACTION TIME: 186 HRS. 158 EXPERIMENT #: 39 REACTION: LMC t0 0010m1te FOSSIL: C0ra111ne A1gae ORIGINAL COMPOSITION: 3.09 m% MgCO3 FINAL COMPOSITION: 49.8 m% CaCO3 SAMPLE NT: 0.1310 gm MOLECULAR NT: 99.59 gm/m01e SUBSTRATE CHEMISTRY: mOTeS Mgz+: 0.00004 m01es Ca2+: 0.00127 SOLUTION CHEMISTRY: 1.5 m1 MgC12 (2M1 3.6 m1 Cac12 (2M)- moTes "92+: 0.0030 m01es 002+: 0.0072 SOLUTION RATIO: mCa2+ __ = 0.71 mCa2+ + InMgz+ SOLID + SOLUTION RATIO: NICa2+ 8 0.74 'ECa2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 398 HRS. 159 EXPERIMENT #: 4O REACTION: LMC t0 DOTOmTte FOSSIL: Echinoid ORIGINAL COMPOSITION: 1.73 m%TMgCO3 FINAL COMPOSITION: 47.8 m% CaCO3 SAMPLE NT: 0.1401 gm MOLECULAR NT: 99.81 gm/moTe SUBSTRATE CHEMISTRY: m01es MgZT: 0.00002 m01es Ca2+: 0.00138 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.6 m1 0:012 (2M) m01es M92+: 0.0030 mo1es Ca2+: 0.0072 SOLUTION RATIO: 01082+ _7— = 0.71 111062+ + mMg2+ SOLID + SOLUTION RATIO: mCa2+ = 0.74 mCa2+ + mMg2+ TEMPERATURE: 250°C ‘REACTION TIME: 398 HRS. 160 EXPERIMENT #: 41 REACTION: HMC t0 DOTOmite FOSSIL: C0ra11ine A1gae; GastrOpOd ORIGINAL COMPOSITION: 10.7 m%.MgCO3 (C.A.); CaC03 (G1 FINAL COMPOSITION: 48.4 m% CaC03 (C.A.): 50.7 m% CaC03 (DOLO) + 0.2 m% MgC03 (LMC) (G) SAMPLE NT: C. ATQae - 0.3457 gm; Gastropod - 0.4068 gm MOLECULAR NT: C. A196e - 97.42 gm/m01e; Gastropod - 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es Mng: C. A1gae - 0.00060; GastrOpod - 0.0000 moTes 002+: C. A1gae - 0.00295; CastrOpOd - 0.0041 SOLUTION CHEMISTRY: 5.0 m1 M9C12 (2M) 9.0 1111 COC12 (2M) m01es MgZT: 0.0100 moTes Ca2+: 0.0180 SOLUTION RATIO: H1032+ __ 8 0.54 111062+ + InMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 126 HRS. 161 EXPERIMENT #: 42 REACTION: LMC t0 0010m1te FOSSIL: Foram ORIGINAL COMPOSITION: 1.9 m%.MgCO3 FINAL COMPOSITION: 51.0 m% CaCO3 SAMPLE HT: 0.0035 gm MOLECULAR NT: 99.78 gm/mOTe SUBSTRATE CHEMISTRY: m01es MgZI: 0.00000067 m01es CaZT: 0.00003441 'SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.7 m1 C0C12 (2M) moles Mgz+: 0.0030 mo1es CaZT: 0.0072 SOLUTION RATIO: mCa2+ 0.71 RaZ'l' + “"92'0' SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 141.5 HRS. 162 EXPERIMENT #: 43 REACTION: LMC t0 DOIOmite FOSSIL: Foram ORIGINAL COMPOSITION: 1.9 m1 MgCO3 FINAL COMPOSITION: 51.1 m% CaCO3 SAMPLE NT: 0.0034 gm MOLECULAR NT: 99.78 gm/mo1e SUBSTRATE CHEMISTRY: m01es Mgz+: 0.00000065 mOTeS CazI: 0.00003343 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.7 m1 CaC12 (2M) m01es M92+: 0.0030 ' moTes Ca2+: 0.0074 SOLUTION RATIO: SOLID + SOLUTION RATIO: mCa2+ __ = 0.71 IIICaZ+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 141.5 HRS. 163 EXPERIMENT #: 45 REACTION: LMC t0 LMC FOSSIL: Foram ORIGINAL COMPOSITION: 3.0 m% MgCO3 FINAL COMPOSITION: 0.7 m% MgC03 SAMPLE NT: 0.0017 gm MOLECULAR NT: 99.62 gm/mo1e SUBSTRATE CHEMISTRY: 0101 es Mgz“: 0.00000051 m01es Ca2+: 0.00001655 SOLUTION CHEMISTRY: 5.2 m1 CaCTz (2M) m01es MgZT: 0.0000 m01es Ca2+: 0.0104 SOLUTION RATIO: mCa2+ 8 1.0 'MCaZI + mMgZ+ SOLID + SOLUTION RATIO: mCa2+ __ = 1.0 mCa2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 129.5 HRS. 164 EXPERIMENT #: 46 REACTION: LMC t0 LMC FOSSIL: Foram ORIGINAL COMPOSITION: 3.0 m% MgC03 FINAL COMPOSITION: 1.2 m% MgCO3 SAMPLE NT: 0.0015 gm MOLECULAR NT: 99.52 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZT: 0.00000045 m01es Ca2+: 0.00001465 SOLUTION CHEMISTRY: 5.2 m1 COC12 (2M) m01es M92+: 0.0000 mOTeS CaZI: 0.0104 SOLUTION RATIO: mCaZ+ = 1.00 ‘MCOZT + mMg2+ SOLID + SOLUTION RATIO: ITICa2+ __ = 1.00 mCa2+ + ITIMg2+ TEMPERATURE: 250°C REACTION TIME: 129.5 HRS. 165 EXPERIMENT #: 47 REACTION: HMC t0 0010m1te FOSSIL: Foram ORIGINAL COMPOSITION: 13.0 m%uMgCO3 FINAL COMPOSITION: 51.1 m% CaCO3 SAMPLE NT: 0.0097 gm MOLECULAR NT: 98.04 gm/mo1e SUBSTRATE CHEMISTRY: (1101 es Mgz“: 0.000012 m01es 062+: 0.000086 SOLUTION CHEMISTRY: 1.5 m1 MgC12 (2M) 3.7 m1 CaC12 (2M) m01es MgZI: 0.0030 m01es 002*: 0.0074 SOLUTION RATIO: NICOZ+ t 0.71 IMCGZ+ + INMg2+ SOLID + SOLUTION RATIO: MC02+ 8 0.71 'MCOZT + mMg2+ TEMPERATURE: 250°C REACTION TIME: 92 HRS. 166 EXPERIMENT #: 48 REACTION: HMC t0 DOTOmTte FOSSIL: Foram ORIGINAL COMPOSITION: 13.0 m%.MgCO3 FINAL COMPOSITION: 52.8 m%.CaCO3 SAMPLE NT: 0.0092 gm MOLECULAR NT: 98.04 gm/mo1e SUBSTRATE CHEMISTRY: m01es Mgz+: 0.000012 mO1es Ca2+: 0.000082 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M1 3.7 m1 C0C12 (2M) m01es M92+: 0.0030 m01es C02+: 0.0074 SOLUTION RATIO: SOLID + SOLUTION RATIO: INCa2+ _._._________. = 0.71 mCa2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 92 HRS. 167 EXPERIMENT #: 49 REACTION: Aragonite t0 DOTOmite FOSSIL: GastrOpOd ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 49.3 m% CaC03 (DOLO) + 0.8 m% MgCO3 (LMC) SAMPLE NT: 0.3783 gm MOLECULAR NT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: 11101 es Mgz": 0. 0000 m01es Ca2+: 0.0038 SOLUTION CHEMISTRY: 2.0 m1 M9012 (2M) 3.0 m1 0:012 (2M) m01es Mng: 0.0040 m01es Ca2+: 0.0060 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 343 HRS. 168 EXPERIMENT #: 50 REACTION: Aragonite t0 0010m1te FOSSIL: Pe1ecypod ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 49.0 m% CaC03 (00L0) + 2.8 m%.MgC03 (LMC) SAMPLE NT: 0.2981 gm MOLECULAR NT: 100.09 gm/mOTe SUBSTRATE CHEMISTRY: m01es Mgz*: 0.0000 mo1es CaZT: 0.0030 SOLUTION CHEMISTRY: 1.9 m1 MgC12 (2M) 3.1 m1 CaCTz (2M) mo1es MgZT: 0.0038 m01es CazT: 0.0062 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 247 HRS. 169 EXPERIMENT #: 52 REACTION: HMC to DOTOmTte FOSSIL: Echinoid ORIGINAL COMPOSITION: 10.7 mZTMgCO3 FINAL COMPOSITION: 50.2 m% CaCO3 SAMPLE NT: 0.2564 gm MOLECULAR NT: 98.40 gm/moIe SUBSTRATE CHEMISTRY: m01es MgZ+: 0.00028 m01es Ca2+: 0.00233 SOLUTION CHEMISTRY: 1.5 1111 Mgc12 (2H) 3.4 m1 CaC12 (2M) m01es MgZT: 0.0030 m01es CaZI: 0.0068 SOLUTION RATIO: mCa2+ __ I 0.59 mCa2+ + InMg2+ SOLID + SOLUTION RATIO: mCa2+ = 0.74 ‘MC62+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 35 HRS. 170 EXPERIMENT #: 53 REACTION: Aragonite t0 0010m1te FOSSIL: Cora1 ORIGINAL COMPOSITION: C0003 FINAL COMPOSITION: 49.1 m% CaC03 SAMPLE NT: 0.3021 gm MOLECULAR NT: 100.09 gm/m01e SUBSTRATE CHEMISTRY: m01es MgZT: 0.0000 m01es 002+: 0.0030 SOLUTION CHEMISTRY: 1.8 m1 MgC12 (2M1 3.2 m1 CaC12 (2M) m01es MgZT: 0.0036 mOTeS C82+: 0.0064 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 326.5 HRS. 171 EXPERIMENT #: 54 REACTION: LMC to Dolomite FOSSIL: Echinoid ORIGINAL COMPOSITION: 1.05 m%)MgCO3 FINAL COMPOSITION: 50.0 m% CaCO3 SAMPLE NT: 0.2205 gm MOLECULAR NT: 99.92 gm/mole SUBSTRATE CHEMISTRY: moles M92+: 0.00002 moles Ca2+: 0.00218 SOLUTION CHEMISTRY: '1.5 ml MgC12 (2M1 3.5 1111 CaC12 (2M) moles MgZT: 0.0032 moles CazT: 0.0070 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 22 HRS. 172 EXPERIMENT #: 55 REACTION: LMC to Dolomite FOSSIL: Coralline Algae ORIGINAL COMPOSITION: 3.6 m% MgC03 FINAL COMPOSITION: 51.1 m% CaCO3 SAMPLE NT: 0.1223 gm MOLECULAR NT: 99.52 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.00004 moles Ca2+: 0.00118 SOLUTION CHEMISTRY: 1.6 m1 M9012 (2M) 3.5 m1 CaClz (2M) moles MgZT: 0.0032 moles Ca2+: 0.0070 SOLUTION RATIO: mCa2+ 0.59 'MCaZT + mMg2+ - SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 22 HRS. 173 EXPERIMENT #: 56 REACTION: Aragonite to LMC FOSSIL: Gastropod; Coral; Pelecypod ORIGINAL COMPOSITION: CaC03 FINAL COMPOSITION: 0.1 - 0.9 m2 M9003 + Trace ARAG (G) SAMPLE NT: Coral - 0.1855; Gastropod - 0.1327; Pelecypod - 0.1016 gm/mole MOLECULAR NT: Coral - 100.09; Gastropod - 100.09; Pelecypod - 100.09 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.0000 moles Ca2+: 0.0042 SOLUTION CHEMISTRY: 5.0 m1 CaC12 (2M) moles MgzI: 0.0000 moles Ca2+: 0.0100 SOLUTION RATIO: SOLID + SOLUTION RATIO: mCa2+ = 1.00 ‘50a2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 11.5 HRS. 174 EXPERIMENT #: 57 REACTION: HMC to Dolomite FOSSIL: Coralline Algae ORIGINAL COMPOSITION: 16.9 111% MgCO3 FINAL COMPOSITION: 49.3 m% CaCO3 SAMPLE NT: 0.2130 9:: MOLECULAR NT: 97.42 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.00037 moles Ca2+: 0.00182 SOLUTION CHEMISTRY: 1.6 m1 MgCIz (2M) 3.5 ml C0012 (2M) moles MgZT: 0.0032 moles Ca2+: 0.0070 SOLUTION RATIO: mCa2+ __ 8 0.59 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: mCaz+ __ = 0.71 mCa2+ + mMgZ+ TEMPERATURE: 250°C REACTION TIME: 120 HRS. 175 EXPERIMENT #: 58 REACTION: HMC to Dolomite FOSSIL: Coralline Algae ORIGINAL COMPOSITION: 16.9 111% MgCO3 FINAL COMPOSITION: 53.6 m% CaCO3 SAMPLE NT: 0.1742 gm MOLECULAR NT: 97.42 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.00030 moles Ca2+: 0.00149 SOLUTION CHEMISTRY: 1.5 m1 M9012 (2M) 3.6 m1 CaClz (2M) moles M92+: 0.0030 moles Ca2+: 0.0072 SOLUTION RATIO: mCa2+ __ = 0.71 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 4.5 HRS. 176 EXPERIMENT #: 59 REACTION: HMC to LMC FOSSIL: Coralline Algae ORIGINAL COMPOSITION: 16.9 m% MgCO3 FINAL COMPOSITION: 2.6 m1 CaCO3 SAMPLE NT: 0.3904 gm MOLECULAR NT: 97.42 gm/mole SUBSTRATE CHEMISTRY: mo1es MgZT: 0.00068 moles Ca2+: 0.00333 SOLUTION CHEMISTRY: 4.9 m1 CaClZ (2M) moles MgZT: 0.0000 moles Ca2+: 0.0098 SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 283 HRS. 177 EXPERIMENT #: 60 REACTION: Aragonite to LMC FOSSIL: GastrOpod; Coral; Pelecypod ORIGINAL COMPOSITION: C0003 FINAL COMPOSITION: 0.1 - 2.5 m% MgC03 + Trace ARAG (P) SAMPLE NT: .5600 gm TOTAL MOLECULAR NT: 100.09 gm/mole SUBSTRATE CHEMISTRY: moles M92+z 0.0000 moles Ca2+: 0.0056 SOLUTION CHEMISTRY: 5.0 m1 CaC12 (2M) moles "92+. 0.0000 moles Ca2+: 0.0100 SOLUTION RATIO: mCa2+ __ = 1.00 mCa2+ + mMg2+ SOLID + SOLUTION RATIO: TEMPERATURE: 250°C REACTION TIME: 11.5 HRS. 178 EXPERIMENT #: 61 REACTION: LMC to Dolomite FOSSIL: Pelecypod ORIGINAL COMPOSITION: 1.4 m%.MgCO3 FINAL COMPOSITION: 60.1 m% CaCO3 (DOLO) + 1.2 m% MgC03 (LMC) SAMPLE NT: 0.3361 gm MOLECULAR NT: 100.09 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.000047 moles Ca2+: 0.003311 SOLUTION CHEMISTRY: 1.9 ml M9C12 (2M) 3.1 NO CaClz (2M) moles MgZT: 0.0038 moles Ca2+: 0.0062 SOLUTION RATIO: SOLID + SOLUTION RATIO: mCa2+ _E = 0.71 mCa2+ + mMg2+ TEMPERATURE: 250°C REACTION TIME: 320 HRS. 179 EXPERIMENT #: 62 REACTION: LMC to Dolomite FOSSIL: Pelecypod ORIGINAL COMPOSITION: 1.4 m2 MgCO3 FINAL COMPOSITION: 60.5 m% CaCO3 (DOLO) + 1.9 m%»MgCO3 (LMC) SAMPLE NT: 0.4131 gm MOLECULAR NT: 100.09 gm/mole SUBSTRATE CHEMISTRY: moles MgZT: 0.000058 moles CaZ+z 0.004070 SOLUTION CHEMISTRY: 2.0 m1 MgC12 (2M) 3.1 mfl CaClz (2M) moles Mng: 0.0040 moles Ca2+: 0.0062 SOLUTION RATIO: mCa2+ = 0.51 ‘mCa2+ + mMg2+ SOLID + SOLUTION RATIO: mCa2+ TEMPERATURE: 250°C REACTION TIME: 320 HRS. 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