Isotopic ratio of sulfur

Sakai H, Casadevall TJ, Moore JG (1982) Chemistry and isotope ratios of sulfur in basalts and volcanic gases at Kilauea volcano, Hawaii. Geochim Cosmochim Acta 46 729-738 Sakai H, DesMarais DJ, Ueda A, Moore JG (1984) Concentrations and isotope ratios of carbon, nitrogen and sulfur in ocean-floor basalts. Geochim Cosmochim Acta 48 2433-2441 Sano Y, Marty B (1995) Origin of carbon in fumaroUc gas from island arcs. Chem Geol 119 265-274... 

Orr, 1974. Changes in sulfur content and isotopic ratios of sulfur during petroleum... 

Orr WL. (1974) Changes in sulfur content and isotopic ratios of sulfur during petroleum maturation. Study of Big Horn Basin Paleozoic oils. Am. Assoc. Pet. Geol. Bull. 50, 2295-318. 

Sulfur (Z = 16) has 4 stable isotopes of which is by far the most abundant in nature (95,02%). The others are - - S (0.75%), (4.21%), and (0.02%). These abundances vary somewhat depending on the source of the sulfur, and this prevents the atomic weight of sulfur being quoted for genera use more precisely than 32.066(6) (p. 17), The variability is a valuable geochemical indication of the source of the sulfur and the isotope ratios of sulfur-containing impurities can even be used to identify the probable source of petroleum samples. ... 

About 2.5 thousand million years ago, the isotopic ratio of sulfur changed, and this has been ascribed to the presence of oxygen on the earth. Oxygen may have originated from some primitive photosynthetic reaction. It is hard to imagine any source other than atmospheric carbon dioxide. Later, 1.7 thousand million years ago, it was certain that O2 existed as one of the major components of the atmosphere. 

Isotope effects also play an important role in the distribution of sulfur isotopes. The common state of sulfur in the oceans is sulfate and the most prevalent sulfur isotopes are (95.0%) and (4.2%). Sulfur is involved in a wide range of biologically driven and abiotic processes that include at least three oxidation states, S(VI), S(0), and S(—II). Although sulfur isotope distributions are complex, it is possible to learn something of the processes that form sulfur compounds and the environment in which the compounds are formed by examining the isotopic ratios in sulfur compounds. 

Kiyosu, Y. (1977b) Sulfur isotope ratios of ores and chemical environment of ore deposition in the Taishu Pb-Zn sulfide deposits, Japan. Geochem. J., 11, 91-99. 

Komuro, K. and Sasaki, A. (1985) Sulfur isotope ratio of framboidal pyrite in Kuroko ores from the Ezuri mine, Akita Prefecture, Japan. Mining Geology, 35, 289-293. 

Fig. 2.56. Sulfur isotope ratios of pyrite from the deposits of the Fujimi and Fudotaki groups of the Hitachi mine (Kase and Yamamoto, 1985).

The mass difference between the two isotopes of sulfur can alter the isotope ratio of a system during chemical and physical transformations (17-21) a process referred to as "fractionation." Quite simply, the zero point energy of a molecule, and hence its rotational and vibrational energy, is mass dependent (22). Therefore, molecules containing different isotopic masses will nave different reactivities and fractionation will occur during mass dependent transformations. 

Sulfur, carbon and hydrogen stable isotope ratios of pyrite, kerogens, and bitumens of two high-sulfur Monterey formation samples from the onshore Santa Maria Basin in California were determined. Kerogens from these were pyrolyzed at 300°C for periods of 2, 10 and 100 hours in closed systems and the yields and isotopic compositions of S-containing fractions (residual kerogens, bitumens and hydrogen sulfide) were determined. 

Figure 6 Variation of sulfur isotope ratios of parent and...

The connection between weathering, evaporation, bacterial activity in marine sediments in shallow water areas and stable sulfur isotope distribution was studied by Holser and Kaplan (1966), Nielsen and Ricke (1969), Nielsen (1968), and Eremenko and Pankina (1972). The sulfur isotope ratios of evaporite sulfates show enrichment of 34S in the Devonian deposits (5 +23 °/oo), a pronounced dip in the Permian ( 5 +12 °/oo), values of +20 °/oo in the Triassic, a fall (+17 to +15 °/oo) in the Jurassic and Cretaceous, stabilizing in the Tertiary to the Recent value of +20 °/oo. 

The natural isotope distribution of sulfur S32 S34 is about 25 1. Therefore each peak in the mass spectrum of a sulfur compound which corresponds to a sulfur-containing fragment is accompanied by a second, shifted by 2 MU (mass units) to higher mass numbers. The intensity ratio of these two peaks depends upon the number of sulfur atoms present in the ion, if the contribution of other fragments to these peaks can be excluded it is 25 1 if only one sulfur is present, 25 2 for two, and so on (Beynon,13 p. 300). Therefore the presence of a sulfur-containing compound and the number of S atoms may be easily deduced from the ratio of the M+ and (M + 2)+ ions. 

The isotope ratios of the sulfur isotopes are also affected by kinetic and equilibrium isotope effects. Kinetic isotope effects are marked in the reduction of sulfates to hydrogen sulfide by bacteria (enrichment of the lighter isotopes in H2S). The equilibrium isotope effect in the reaction... 

Sakai H., Desmarais D. J., Uyeda A., and Moore J. G. (1984) Concentration and isotope ratios of carbon nitrogen and sulfur in ocean floor basalts. Geochim. Cosmochim. Acta 48, 2433 - 2441. 

Carpenter S. J. and Lohmann K. C. (1997) Carbon isotope ratios of Phanerozoic marine cements re-evaluating the global carbon and sulfur systems. Geochim. Cosmochim. Acta 61, 4831-4846. 

Compound-specific isotope analysis Determination of the isotopic ratio of the carbon, nitrogen, hydrogen, sulfur, or oxygen contents of a single compound. The isolation of the single compound is usually achieved by some form of either off-line or on-line preparation in which gas chromatography is an important step. 

The basic difference between the formation of sulfur and the carbon gases and its influence on the isotopic ratios of kerogen, bitumen, oil and gas lies in the chemical activity of the thermally derived fragments. Both elemental sulfur and hydrogen sulfide formed at elevated temperatures could re-react with all fractions (Stoler et al., 2003). Research on changes in both carbon and... 

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