Sulfur isotopes exchange

Ripley EM, Li C (2003) Sulfur isotope exchange and metal enrichment in the formation of magmatic Cu-Ni-(PGE)-deposits. Econ Geol 98 635-641 Robert F (2001) The origin of water on Earth. Science 293 1056-1058... 

Sulfur isotope exchange between sulfate and sulfide. Ohmoto and Lasaga (1982) investigated the kinetics of sulfur isotope exchange between aqueous sulfates and sulfides at hydrothermal conditions ( 200 to 400°C). They concluded that the rates of chemical reactions between sulfates and sulfides are essentially identical to the sulfur isotope exchange rates because both the chemical and isotopic reactions involve simultaneous oxidation of sulfide-sulfur atoms and reduction of sulfate-sulfur. They expressed the rate of reaction as a second order rate law... 

Huff GA, Satterfield CN (1984) Intrinsie kineties of the Fiseher-Tropseh synthesis on a reduced fused-magnetite catalyst. Ind Eng in Chem Prod Res Develop 23 851-954 Humayun M, Clayton R (1995) Potassium isotope cosmochemistiy—genetic-implications of volatile element depletion. Geoehim Cosmoehim Acta 59 2131-2148 Igunmov SA (1976) Sulfur isotope exchange between sulfide and sulfate in hydrothermal solutions. Geokhimiya 4 497-503... 

Fossing, H., Thode-Andersen, S. and Jorgensen, B.B., 1992. Sulfur isotope exchange between 35S-labeled inorganic sulfur compounds in anoxic marine sediments. Marine Chemistry, 38 117-132. 

Only within the past few years have serious attempts been made to estimate quantitatively the differences in reactivity between thiophene and benzene and between the 2- and 3-position of thiophene. Careful investigation on the acid-induced exchange of deuterium and tritium have shown that the ratios of the exchange rates in the 2- and 3-positions are 1045 61 for deuterium and 911 60 for tritium in 57% by weight aqueous sulfuric acid at 24.6°C. A kinetic isotope effect in the isotopic exchange has been found to be k-r/kr, = 0.51 0.03 in the 2-position and kr/kjy — 0.59 0.04 in the... 

The isotopic exchange between radioactive elemental sulfur containing traces of and aqueous polysulfide at pH=7.6 has been shown to be very rapid. Within less than 2 min half of the tracer from had exchanged [77],... 

The most notable feature of the sulfur isotope geochemistry of lunar rocks is the uniformity of 8 " S-values and their proximity to the Canyon Diablo standard. The range of published 8 " S-values is between -2 to +2.5%o. However, as noted by Des Marais (1983), the actual range is likely to be considerably narrower than 4.5%o due to systematic discrepancies either between laboratories or between analytical procedures. The very small variation in sulfur isotope composition supports the idea that the very low oxygen fugacities on the Moon prevent the formation of SO2 or sulfates, thus eliminate exchange reactions between oxidized and reduced sulfur species. 

Paytan A, Luz B, Kolodny Y, Neori A (2002) Biologically mediated oxygen isotope exchange between water and phosphorus. Global Biogeochem Cycles 16-13 1-7 Paytan A, Kastner M, Campbell D, Thiemens M (2004) Seawater sulfur isotope fluctuations in the Cretaceous, Science 304 1663-1665... 

Another possible source of chemical MIF is self-reaction of the SO radical, which either yields S and SO2 as disproportionation products [41], or the SO dimer as an association product [42]. Two of the four lowesf energy singlef sfafes of the SO dimer [43] have a reduced point group symmetry upon sulfur isotope substitution. If sulfur atom exchange is another possible outcome in the self reaction of SO, then a symmetry-derived mass-independent effect analogous to O3 formation may be possible. A similar conclusion may be drawn for the triplet states of the SO dimer. 

The acidification of H2 may also be involved in hydrogenase action, where H2 is beheved to bind to an Fe(II) center. Isotope exchange between H2 and D2O is catalyzed by the enzyme see Nickel Enzymes Cofactors Nickel Models of Protein Active Sites Iron-Sulfur Proteins). Similar isotope exchange can also occur in H2 complexes. Oxidative addition to give a classical dihydride is also a common reaction. [W(H2)(CO)3(PCy3)2] is in equilibrium with about 20% of the dihydride in solution. This can lead to subsequent hydrogenolysis of M-C bonds as in the case of a cyclometallated phenylpyridine complex of Ir(III). ... 

Alt J. C. (1995) Sulfur isotopic profile through the oceanic crust sulfur mobility and seawater-crustal sulfur exchange during hydrothermal alteration. Geology 23(7), 585-588. 

Figure 17 shows schematically the major transformations of sulfur in aquatic systems and their related isotopic fractionations. Processes that do not significantly fractionate sulfur isotopes include (i) weathering of sulfide and sulfate minerals, (ii) adsorption-desorption interactions with organic matter, and (iii) isotopic exchange between S04 and HS or H2S in low-temperature environments. Precipitation of sulfate minerals is accompanied by only slight isotopic fractionation, and the precipitates are generally... 

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