A 33S Anomaly in the allende meteorite

The isotope ratios ³³S/³²S and ³⁴S/³²S have been measured in sulphur fractions extracted from samples of the meteorites Allende and Eagle Station by leaching at successively greater acid concentrations and higher temperatures. On a three isotope plot of δ³³S$\text{vs}$δ³⁴S most of the data lie on or close to the mass fractionation line. The last fraction of sulphur extracted from a bulk Allende sample lies off the line and has an approximately 1%. excess in the ³³/³²S ratio.Previous searches for anomalous abundance patterns of ³²S, ³³S, ³⁴S and ³⁶S have been reported by HULSTON and THODE (1965a,b), THODE and REES (1971), and REES and THODE (1972). No isotope abundance variations were found, in the meteorite and lunar samples studied, which could not be explained on the basis of either mass dependent isotope fractionation or, in the special case of iron meteorites, cosmic ray production of ³³S and ³⁶S. We report here preliminary results of a renewed search for isotopically anomalous sulphur in which we are concentrating on the Allende and Eagle Station meteorites, both of which contain anomalous oxygen (CLAYTON $\text{et}$$\text{al}$., 1973, 1976). In a first attempt to distinguish between normal sulphur and any possible anomalous sulphur, we have leached both bulk samples and hand separated components of these meteorites with hydrochloric acid.CLAYTON and RAMADURAI (1977) suggested that the presence of isotopically anomalous sulphur would be evidence for the existence of presolar grains which are relics of nucleosynthesis in certain zones of supernova expansion. In particular they suggested that sulphides of titanium are good candidates for isotopic analysis. These are not expected to exist in conventional solar equilibrium condensation sequences, but might be abundant in condensates from silicon burning shells of supernovae. Our chemical procedures were already completed when CLAYTON and RAMADURAI'S suggestions came to our attention and it must be stressed that so far, in all cases but one we have examined only sulphur from sulphides which are decomposed by HC1. Thus we may not have sampled sulphides of the type suggested by CLAYTON and RAMADURAI.All samples of the Allende meteorite were ground finer than 50μm before acid extraction of sulphur. Samples of sulphur were extracted from the various phases of the meteorites by using successively stronger hydrochloric acid leaches, longer times and higher temperatures of reaction. Sulphur initially released as H₂S was successively converted to CdS, Ag₂S and SF₆, this latter compound being analysed mass spectrometrically (THODE and REES, 1971). Analyses of nine SF₆ samples prepared from Ag₂S originally derived from Canyon Diablo troilite were also performed in order to monitor fluorination and mass spectrometry precision and to establish the zero points ofthe isotope variation scales. The results are shown in Table 1. The sulphur contents of the various samples were determined gravimetrically as Ag₂S. The bulk and matrix samples are probably a few percent low because of mechanical losses. The percentages of sulphur in each fraction of a sample extracted during each leaching stage are given in the table. The total sulphur content in the bulk and matrix samples of the Allende meteorite i.e., the sum of the sulphur contents of the individual fractions, varies from 1.8 to 2.08%, the highest percentage being in the matrix. These values compare with about 2 to 2.1% obtained by CLARKE $\text{et}$$\text{al}$. (1970).     

Sulphur isotope effects in the dissociation and evaporation of troilite: A possible mechanism for 34S enrichment in lunar soils

Both the dissociation and evaporation of troilite. heated to its melting point in vacuo, are isotopically selective. The elemental sulphur from the dissociation of troilite has a ${}^{34}\text{S}{}^{32}\text{S}$ ratio which is 13.0‰ less than that of the undissociated material while the ${}^{34}\text{S}{}^{32}\text{S}$ ratio in evaporated troilite is 5.4‰ less than that of the residual material. The two processes occur simultaneously and the isotopic variations during the course of the reaction are in accord with those for a branched reaction where the unreacted material remains isotopically well-mixed, as in a Rayleigh distillation process. This isotopic selectivity must be taken into account, along with that in other lunar surface processes, when considering the heavy isotope enrichment of sulphur in lunar soils.     

Stable sulfur and nitrogen isotopic compositions of crude oil fractions from Southern Germany

Eleven samples of crude oil from the Molasse Basin of Southern Germany were fractionated and their contents of sulfur and nitrogen as well as the stable isotope compositions of these elements (${}^{34}\text{S}{}^{32}\text{S}$ and ${}^{15}\text{N}{}^{14}\text{N}$, resp.) investigated.According to the δ³⁴S determinations, all crude oils from the Tertiary base of the Western and Eastern Molasse belong to one oil family and differ significantly from the Triassic and Liassic oils in the Western Molasse.An enrichment of ³⁴S was observed with increasing polarity of crude oil fractions. The isotope distributions of sulfur in the polar constituents of the biodegraded oils from the sandstones of Ampfing, however, approach a homogeneous distribution.The nitrogen isotope distribution is rather uniform in Southern German oils. A regional differentiation can be recognized, although the overall isotopic variation is small. The δ¹⁵N values of the crudes and asphaltenes do not correlate.     

Sulfur isotope study of Quaternary volcanic rocks from the Japanese Islands Arc

The sulfide and sulfate contents and their δ³⁴S values were determined in Quaternary volcanic rocks from the Japanese Islands Arc. The total sulfur contents are much lower (less than 40 ppm) and the δ³⁴S values are higher (+4.4 ± 2.1) than those of ocean-floor basalts (800 ± 100 ppm and +0.8 ± 0.5, respectively; Moore and Fabbi, 1971; Sakaiet al., 1982). Lateral variations of both sulfur content and δ³⁴S values were observed in the four volcanic belts in Japan. In the Northeast Japan belt, the sulfur content (30 ± 10 ppm) of the rocks in the inner zone (the Japan Sea side) is 3 to 5 times that in the outer zone (the Pacific side), although the δ³⁴S values of the two zones are almost the same (+4.3 ± 1.0). The δ³⁴S values for the two belts in West Japan are on the average 2%. higher than those of East Japan.This study suggests that the primary magmas that formed the island arc volcanic rocks are initially depleted in sulfur (<120 ppm) and enriched in ³⁴S ($\text{δ}{}^{34}\text{S: +5 ～ +7}$) compared to ocean-floor tholeiitic basalts which formed at mantle under oceanic region. This indicates that the upper-mantle is heterogeneous in sulfur content and isotope composition.     

Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano,Hawaii

Eighteen basalts and some volcanic gases from the submarine and subaerial parts of Kilauea volcano were analyzed for the concentration and isotope ratios of sulfur. By means of a newly developed technique, sulfide and sulfate sulfur in the basalts were separately but simultaneously determined. The submarine basalt has 700 ± 100 ppm total sulfur with δ³⁴S_Σs of $\text{0.7 ± 0.1 ‰}$. The sulfate/sulfide molar ratio ranges from 0.15 to 0.56 and the fractionation factor between sulfate and sulfide is $\text{+7.5 ± 1.5‰}$. On the other hand, the concentration and δ³⁴S_Σs values of the total sulfur in the subaerial basalt are reduced to 150 ± 50 ppm and $\text{?0.8 ± 0.2‰}$, respectively. The sulfate to sulfide ratio and the fractionation factor between them are also smaller, 0.01 to 0.25 and +3.0‰, respectively. Chemical and isotopic evidence strongly suggests that sulfate and sulfide in the submarine basalt are in chemical and isotopic equilibria with each other at magmatic conditions. Their relative abundance and the isotope fractionation factors may be used to estimate the $\text{?o}{}_2$ and temperature of these basalts at the time of their extrusion onto the sea floor. The observed change in sulfur chemistry and isotopic ratios from the submarine to subaerial basalts can be interpreted as degassing of the SO₂ from basalt thereby depleting sulfate and ³⁴S in basalt.The volcanic sulfur gases, predominantly SO₂, from the 1971 and 1974 fissures in Kilauea Crater have δ³⁴S values of 0.8 to 0.9%., slightly heavier than the total sulfur in the submarine basalts and definitely heavier than the subaerial basalts, in accord with the above model. However, the δ³⁴S value of sulfur gases (largely SO₂) from Sulfur Bank is 8.0%., implying a secondary origin of the sulfur. The δ³⁴S values of native sulfur deposits at various sites of Kilauea and Mauna Loa volcanos, sulfate ions of four deep wells and hydrogen sulfide from a geothermal well along the east rift zone are also reported. The high δ³⁴S values (+5 to +6%._o) found for the hydrogen sulfide might be an indication of hot basaltseawater reaction beneath the east rift zone.     

Sulphur isotope geochemistry of carbonatites

Sulphur isotopic data for sulphides and barite from several carbonatites (Mountain Pass, Oka, Magnet Cove, Bearpaw Mountains, Phalabora) show that individual carbonatites have different mean sulphide or barite isotopic compositions which deviate from the meteoritic mean $\text{δ}{}^{34}\text{S(0‰)}$.Classification of carbonatites in terms of T,?O₂ and pH during formation of the sulphur-bearing assemblages indicates that with decreasing T and increasing relative ?O₂ the mean δ³⁴S sulphide becomes increasing negative relative to the mean magma δ³⁴S. Only barite-free high temperature carbonatites (Phalabora) in which the mean δ^34S sulphide approaches the mean magmaδ³⁴S as a consequence of the paucity of oxidized anionic sulphur species in the magma can be used to directly estimate the mean isotopic composition of the source material.Barites from the Mountain Pass carbonatite show an increase in δ³⁴S with sequence of intrusion of the carbonatite units; dolomitic carbonatite (mean δ³⁴S, + 5.4‰), calcitic carbonatite (+ 4.8%.), silicified carbonatite (+ 6.9‰), tabular carbonatite dikes (+ 8.7‰), mineralized shear zones (+ 9.5‰). Within each of these units a spread of 6.8%. is evident. Isotopic trends in this low temperature (300°C) carbonatite are evaluated by treating the system as a hydrothermal fluid. The observed isotopic variations can be explained by removal of large amounts of sulphur from a fluid whose mean δ³⁴S is 0 to + 1‰     

Light element geochemistry of the Apollo 16 site

Pronounced variations in abundances and isotopic compositions of some light elements in soils from the Apollo 16 site are interpreted in terms of differing degrees of solar wind exposure for an originally, and approximately, homogeneous regolith. Carbon abundances in soils are compatible with a model in which equilibrium is established, after 10⁴-10⁵ yr, between solar wind input and loss by H stripping. However, this model does not explain the observed C isotopic distribution, suggesting that other sources of C or other processes, or both, are also important. Carbon abundances in rocks from Apollo 16 are higher (average 40 ppm) than at other landing sites although their isotopic compositions, ?35 < δ¹³C < ?16%. PDB, are normal. Abundances of N and, to a less extent, He and H in soils correlate with C as does a fraction of metallic Fe attributed to in situ reduction of indigenous Fe²⁺ by solar wind H.Fillet soil 67461 apparently contains solar wind C and N in a relatively unfractionated form, yielding an upper limit to solar wind (δ¹³C of ?16%., PDB and a value of 3.4 for $\text{C}\text{N}$ in the solar wind.Sulfur at the Apollo 16 site represents a paradox in that, although abundances in soils are apparently controlled by local rock S contents, they also correlate, for all but one sample, with δ³⁴S, which itself is apparently controlled by surface exposure age. A complex lunar S cycle is suggested.     

Hydrogen and carbon isotopes of petroleum and related organic matter

$\text{D}\text{H}$ and ${}^{13}\text{C}{}^{12}\text{C}$ ratios were measured for 114 petroleum samples and for several samples of related organic matter. δD of crude oil ranges from ?85 to ?181‰, except for one distillate (?250‰) from the Kenai gas field; δ¹³C of crude oil ranges from ?23.3 to ?32.5‰, Variation in δD and δ¹³C values of compound-grouped fractions of a crude oil is small, 3 and 1.1%., respectively, and the difference in δD and δ¹³C between oil and coeval wax is slight. Gas fractions are 53–70 and 22.6–23.2‰ depleted in D and ¹³C, respectively, relative to the coexisting oil fractions.The δD and δ¹³C values of the crude oils appear to be largely determined by the isotopic compositions of their organic precursors. The contribution of terrestrial organic debris to the organic precursors of most marine crude oils may be significant.     

Geographical trends of carbon and sulphur isotope abundances in human kidney stones

$\text{δ}{}^{13}\text{C}$ values and $\text{δ}{}^{34}\text{S}$ values in human kidney stones range from ?24 to ?10 and ?10 to + 20 %., respectively, and depend upon geographical location. Although the distributions overlap, the mean $\text{δ}{}^{13}\text{C}$ values in oxalate stones from North America become less negative with decreasing latitude. For Mexico and Hawaii, the distributions appear to be bimodal. Uric acid stones are generally enriched in ¹³C by up to 7%. in comparison to oxalates from the same location, whereas cystine stones tend to span the ranges of both stone types. The geographical trends can be explained by the relative proportions of dietary carbon derived ultimately from plants undergoing various established photosynthetic mechanisms (C₃, C₄, CAM). The differences among the various major stone types may reflect isotope fractionation during biochemical conversions.Exogenic oxalates and uric acid are considered to have little role in precipitating the respective minerals. Whereas, the currently available C isotope data support this contention, more data are desirable, particularly for ingested oxalates. In contrast, S isotope data provide strong evidence that cystine stones are derived from ingested organo-S compounds and bear no relation to inorganic sulphate consumed by the individual. In turn, these organic-S compounds were probably derived from sulphate in the hydrosphere at lower levels in the food chain, e.g., by bacterial assimilation.     

Trapped solar wind noble gases and exposure age of Luna 16 lunar fines

He, Ne, Ar, Kr and Xe concentrations and isotopic abundances were measured in three bulk grain size fractions prepared from sample L-16-19, No. 120 (C level, 20–22 cm depth) returned by the Luna 16 mission. The expected anticorrelation between the concentrations of trapped solar wind noble gases and grain size is observed. Elemental abundances of solar wind trapped noble gases are similar to those previously found in corresponding grain size fractions of the Apollo 11 and 12 fines. The trapped ratio ${}^4\text{He}{}^{20}\text{Ne}$ varies in the soils from different lunar maria due to diffusion losses. A rough correlation of ${}^4\text{He}{}^{20}\text{Ne}$ with the proportion of ilmenite in these samples is apparent. The elemental and isotopic ratios of the surface correlated noble gases in Luna 16 resemble those previously found in Apollo fines. Based on ²¹Ne, ⁷⁸Kr and ¹²⁶Xe a cosmic ray exposure age of 360 my was determined. This age is similar to those obtained for the soils from other lunar maria.     

Carbon,nitrogen and sulfur in lunar fines 15012 and 15013: abundances,distributions and isotopic compositions

Lunar fines 15012,16 and 15013,3 were analyzed by stepwise pyrolysis and acid hydrolysis as well as complete combustion in oxygen to determine carbon, nitrogen and sulfur. In addition, hydrogen was analysed during pyrolysis as well as during hydrolysis. In the former case, it was released by mineral grains to which it was adsorbed or from cavities within which it had been captured. Hydrogen released during hydrolysis had largely resulted from dissolution of metallic iron.By comparison of the distribution frequencies of C, N, S, H₂ and Fe with ⁴He, considered to have arisen from solar wind contribution, it is concluded that nitrogen and hydrogen have largely a solar origin. Carbon has a significant solar contribution, and metallic iron may have resulted from solar wind interaction with ferrous minerals on the lunar surface. Sulfur probably has a predominantly lunar origin. There is no direct evidence for meteoritic contribution to these samples.Solar wind interaction also has a marked effect on the stable isotope distribution of ¹³C/¹²C, ¹⁵N/¹⁴N, and ³⁴S/³²S. In all cases, the heavy isotope was most enriched in the smallest grain-size fraction. During stepwise pyrolysis, CH₄, CO₂, CO and N₂ were obtained at different temperatures and displayed different isotopic ratios. The carbon fraction most enriched in ¹³C, was CH₄ liberated at 600–800°C with $\text{δ}{}^{13}\text{C = +45.7\%.}$. Between 400 and 600°C, N₂ was liberated with (δ¹⁵N ≈ +119% and at 600–800°C, N₂ was liberated with $\text{δ}{}^{15}\text{N = +75\%.}$ relative to terrestrial atmospheric nitrogen.     

The sulphur isotope systematics of the Taolin lead-zinc ore deposit,China

Sulphur isotope data from coexisting sulphides and sulphates from the Taolin Pb-Zn ore deposit have been used to estimate the temperatures of sulphur mineral precipitation. The data indicate that sulphide was the dominant sulphur species in solution at high temperatures and that sulphate was dominant at low temperatures. Also the data show that the δ³⁴S value of total sulphur in solution was close to zero at high temperatures (~325°C) but had high positive values (+15%.) at low temperatures (~250°C). We interpret this phenomenon in terms of the effects of mineral precipitation on the isotopic composition of the solution. The increase in the δ³⁴S value of total sulphur with decreasing temperature was brought about by the removal from the system, by precipitation, of isotopically light sulphides.     

Isotopic abundances of water of crystallization of gypsum from the Miocene evaporite formation,Carpathian Foredeep,Poland

For sulfates of Miocene evaporites in the Carpathian Foredeep, the waters of crystallization of gypsum (w.c.g.) have $\text{δD = ?38 to ?113\%.}$ and $\text{δ}{}^{18}\text{O = 0 to ?11\%.}$ (SMOW). The $\text{δ}{}^{34}\text{S}$ and $\text{δ}{}^{18}\text{O}$ values of the sulfates are uniform and consistent with a marine origin. It is proposed that the original w.c.g. was equilibrated with marine water. Subsequently, it re-equilibrated towards very isotopically light water (δD ～ ?100%., δ¹⁸O ～ ?14%) during a glacial or postglacial period and is now trending towards current waters circulating through the deposits (δD ～ ?50%., δ¹⁸ ～ ?7%). The extent of reequilibration increased with decreasing crystal size.     

The geochemistry of the stable isotopes of silicon

One hundred thirty two new measurements of the relative abundances of the stable isotopes of silicon in terrestrial materials are presented. The total variation of ^δ30Si found is 6.2%., centered on the mean of terrestrial mafic and ultramafic igneous rocks, δ³⁰Si = ?0.4%.. Igneous rocks show limited (1.1%.) variation; coexisting minerals exhibit small, systematic silicon isotopic fractionations that are roughly $\text{1}\text{3}$ the magnitude of concomitant oxygen isotopic fractionations at 1150°C. In both igneous minerals and rocks, δ³⁰Si shows a positive correlation with silicon content, as does δ¹⁸O. Opal from both sponge spicules and sinters is light, with $\text{}\text{?}\text{gd}{}^{30}\text{Si}\text{= ?2.3}$ and ?1.4%., respectively. Large ^δ30Si values of both positive and negative sign are reported for the first time from clay minerals (?2.3 to +1.8%.), opaline phytoliths (?1.4 to +2.8%.), and authigenic quartz (+ 1.4%.). All highly fractionated samples were precipitated from solution at low temperatures; however, aqueous silicon is not measurably fractionated relative to quartz at equilibrium. A kinetic isotope fractionation of ≈3.5%. is postulated to occur during the low temperature precipitation of opal and, possibly, poorly ordered phyllosilicates, with the silicate phase being enriched in ²⁸Si. This fractionation, coupled with a Rayleigh precipitation model, is capable of explaining most non-magmatic δ³⁰Si variations. Chert ^δ30Si values are largely inherited, but the primary opal ^δ30Si values can be modified by isotopic equilibration of silicate silicon and dissolved silicon during the transformation of opal into quartz.     

Revised estimate of δ34S for marine sulfates from the Upper Ordovician: data from the Williston Basin,North Dakota,U.S.A.

Analyses for δ³⁴S of 13 bedded, marine anhydrite samples from the “C” anhydrite member of the Red River Formation (Upper Ordovician) in the North Dakota portion of the Williston basin represent an addition of δ³⁴S data to a portion of the S isotope age curve with few data. Previously published estimates of δ³⁴S for Upper Ordovician marine sulfates apparently are limited to 4 samples from the Saskatchewan portion of the same basin. An adjusted mean value of +25.5‰ was calculated for all known Upper Ordovician δ³⁴S determinations. This value is approximately 2 to 3‰ lighter than the previous estimate, which suggests that δ³⁴S of the world ocean during the Upper Ordovician may have been lighter than previously thought. However, because all δ³⁴S data are from one sedimentary basin, additional S isotopic data from several globally-distributed evaporite basins are needed to evaluate this hypothesis and further constrain δ³⁴S for the Upper Ordovician. Similar re-examination of other portions of the S isotope age curve with limited amounts of data may increase our understanding of the secular variation in δ³⁴S.     

Variations in composition and δ18O values within the Kaffo albite—Riebeckite granite of Liruei Complex,Younger Granites of Nigeria

The peralkaline Kaffo albite—riebeckite granite is an albitised, low-temperature intrusion in Liruei Complex, one of the oldest of the ring-complexes in the Younger Granite province of Nigeria. Analyses of borehole samples from different parts of the intrusion show it to be compositionally heterogeneous, especially in respect of Si, Al, Na, K and F distribution and this, in part, can be correlated with the variable degree of albitisation. Isotopically the granite is a normal plutonic type with δ¹⁸ O values of $\text{+ 8.1 ± 0.2‰}$, and albitisation does not seem to have been accompanied by exchange of isotopes between albitising fluid and the granite. Co-existing riebeckitic-arfvedsonite and aegirine pairs from borehole samples show extreme enrichment in Na and Fe; the amphibole also shows considerable substitution of Fe by Ti, Zn and Mn, and of OH by F. Isotopically the amphibole and pyroxene are different from others, having low, variable δ¹⁸ O values (+5.3–+6.4 and $\text{+4.4–+5.1‰}$, respectively), and the fractionation value Δ Px — Am is always large, negative and constant (—$\text{1.2 ± 0.2‰}$). The low δ¹⁸ O values are considered to be due to special features of the crystal chemistry of the alkali amphiboles and pyroxenes, and the spread of each set of values may be due to sub-solidus isotope exchange between the minerals and albitising fluid.     

The enrichment of 34S in the solfataras of the Nea Kameni volcano,Santorini archipelago,Greece

Sulfur isotope investigations carried out on elemental sulfur and sulfates of the Nea Kameni solfataras, Santorini, Aegean Sea, Greece, show a clear enrichment in the heavy sulfur isotope ³⁴S against the assumed primordial ${}^{32}\text{S}{}^{34}\text{S}$ ratio of 22,220. Within the same crater, different vents, only a few meters apart from each other, produced δ differences up to 10‰, which remained constant for several years. This enrichment is most probably due to contamination by heavy sulfur from a nonvolcanic source. An enrichment in the same order of magnitude was observed in sulfur of recent and older lavas ($\text{δ}{}^{34}\text{S}\text{= ?1 ? +11‰}$).Potential contaminants like sulfide sulfur in hydrothermal ore veins of Athinios has a δ ³⁴S mean value close to 0‰, sulfide and sulfate in the sedimentary basement has a δ ³⁴S mean value of $\text{+2.6‰.}$ Seawater sulfate from the area gives a value of $\text{δ}{}^{34}\text{S}\text{= 20‰}$, while sulfide from bacterial reduction of pore-water sulfate in recent iron ore sediments has δ ³⁴S values between ?8 and $\text{?5‰.}$ Sulfate remaining in the pore solutions gave $\text{δ}{}^{34}\text{S}\text{= +27‰}$.The most probable explanation for the observed high δ ³⁴S values in the solfataric sulfur and in some of the lavas of the Santorini area is contamination of the volcanic vents by Mediterranean Sea water.     

Isotopic evidence for the origin of sulfur in the Herrin (no. 6) coal member of Illinois

The sulfur isotopic composition of the Herrin (No. 6) Coal from several localities in the Illinois Basin was measured. The sediments immediately overlying these coal beds range from marine shales and limestones to non-marine shales. Organic sulfur, disseminated pyrite, and massive pyrite were extracted from hand samples taken in vertical sections.The $\text{δ}{}^{34}\text{S}$ values from low-sulfur coals (< 0.8% organic sulfur) underlying nonmarine shale were +3.4 to +7.3%₀ for organic sulfur, +1.8 to +16.8%₀ for massive pyrite, and +3.9 to +23.8%₀ for disseminated pyrite. In contrast, the $\text{δ}{}^{34}\text{S}\text{values from high-sulfur coals}$ (> 0.8% organic sulfur) underlying marine sediments were more variable: organic sulfur, ?7.7 to +0.5%₀, pyrites, ?17.8 to +28.5%₀. In both types of coal, organic sulfur is typically enriched in ³⁴S relative to pyritic sulfur.In general, δ ³⁴S values increased from the top to the base of the bed. Vertical and lateral variations in δ ³⁴S are small for organic sulfur but are large for pyritic sulfur. The sulfur content is relatively constant throughout the bed, with organic sulfur content greater than disseminated pyrite content. The results indicate that most of the organic sulfur in high-sulfur coals is derived from post-depositional reactions with a ³⁴S-depleted source. This source is probably related to bacterial reduction of dissolved sulfate in Carboniferous seawater during a marine transgression after peat deposition. The data suggest that sulfate reduction occurred in an open system initially, and then continued in a closed system as sea water penetrated the bed.Organic sulfur in the low-sulfur coals appears to reflect the original plant sulfur, although diagenetic changes in content and isotopic composition of this fraction cannot be ruled out. The wide variability of the δ ³⁴S in pyrite fractions suggests a complex origin involving varying extents of microbial H₂S production from sulfate reservoirs of different isotopic compositions. The precipitation of pyrite may have begun soon after deposition and continued throughout the coalification process.     

Stable isotopic investigations of early development in extant and fossil chambered cephalopods I. Oxygen isotopic composition of eggwater and carbon isotopic composition of siphuncle organic matter in Nautilus

Eggwaters from the chambered cephalopod Nautilus are depleted in both ¹⁸O and deuterium relative to ambient seawater. Eggwaters from six other species, including the related chambered cephalopod Sepia, do not show such depletion. These observations indicate that the previously observed step towards more positive $\text{δ}{}^{18}\text{O}$ values in calcium carbonate laid down after Nautilus hatches, relative to carbonate precipitated prior to hatching, can be explained by equilibration of the carbonate with water in the egg before hatching and with seawater after hatching. The presence of an oxygen isotope difference between eggwater and seawater for Nautilus and its absence for Sepia suggest that hatching will be recorded in the $\text{δ}{}^{18}\text{O}$ values of shell carbonates for some but not all extinct and extant chambered cephalopods.The $\text{δ}{}^{13}\text{C}$ values of the organic fraction of the siphuncle in Nautilus do not show any consistent pattern with regard to the time of formation before or after hatching. This observation suggests that the minimum in $\text{δ}{}^{13}\text{C}$ values previously observed for calcium carbonate precipitated after Nautilus hatches is not caused by a change in food sources once the animal becomes free-swimming, as has been suggested.     

Hydrogen,oxygen and carbon isotopic evidence for the origin of rodingites in serpentinized ultramafic rocks

$\text{D}\text{H}$, ${}^{18}\text{O}{}^{16}\text{O}$ and ${}^{13}\text{C}{}^{12}\text{C}$ analyses were made of 14 whole rock and 28 mineral samples of rodingites associated dominantly with lizardite-chrysotile serpentinites from the West Coast of the U.S.A., New Zealand, and the Northern Appalachian Mtns. The δD values of the rodingite minerals are in three groupings: 5 monomineralic veins of pectolite, ?281 to ?429; 8 monomineralic veins of xonotlite, ?112 to ?135; all other minerals, including hydrogarnet, idocrase, prehnite, actinolite, nephrite, and chlorite, ?34 to ?80. Most calcites in rodingites have δ¹⁸O (+9.3 to +14.4) and (δ¹³C (?6.7 to +0.9) values similar to calcites in other Franciscan rocks, but distinct from the very low temperature calcite veins in serpentinites. The $\text{D}\text{H}$ data, combined with δ¹⁸O values of xonotlite (+5.7 to +10.9) and pectolite (+8.9 to +12.4) suggest formation from meteoric-type waters at low temperatures; the $\text{D}\text{H}$ depletion of pectolite, however, is anomalous. Rodingite whole rock values range from δ¹⁸O = +4.1 to +11.5 and δD = ?50 to ?86; one sample containing minor amounts of lizardite-chrysotile serpentinite has δD = ?92, outside this range. However, most rodingites of basaltic or gabbroic parentage are more restricted in δ¹⁸O (+4.1 to +8.6). Such a wide range in δ¹⁸O is consistent with the idea that most rodingites form over a relatively broad range of hydrothermal temperatures. Hydrogen isotopic data for most rodingite minerals (except xonotlite and pectolite) and for whole rocks are suggestive of non-meteoric waters. These $\text{D}\text{H}$ data overlap those observed for veins of hydrous minerals found in Franciscan igneous rocks studied by Margaritz and Taylor (1976, Geochim. Cosmochim. Acta40, 215–234), possibly suggesting evolved D-enriched, connate type metamorphic waters generated during high P, low T Franciscan-type metamorphism at temperatures (250–500°C) comparable to estimates based on mineral stabilities. Such an interpretation is supported by the ${}^{18}\text{O}{}^{16}\text{O}$ and ${}^{13}\text{C}{}^{12}\text{C}$ data for calcite in rodingites.The isotope data appear to contradict some of the conclusions derived from geologic and petrologic studies that indicate concomitant metasomatism and serpentinization of their presently observed host rock. These data appear most consistent with the interpretation that most rodingite minerals, with the exception of late-stage veins of xonotlite and possibly pectolite, may involve metasomatism in association with antigorite serpentinization of ultramafic rock. Subsequent upward tectonic transport in many instances may result in incorporation of the rodingites into their presently observed lizarditechrysotile host rock during or subsequent to pervasive shallow level serpentinization by meteoric waters.