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The role of organic acid in the abiogenic reduction of sulfate and the sulfur isotope effect.

1990; The Geochemical Society of Japan; Volume: 24; Issue: 1 Linguagem: Inglês

10.2343/geochemj.24.21

1880-5973

Yasuhiro Kiyosu, H. R. Krouse,

Paleontology and Stratigraphy of Fossils

Abiogenic reduction of sulfate by acetic acid has been conducted at temperatures ranging from 241 to 340°C. The sulfides produced and the remaining sulfates have been chemically and isotopically quantified. The reaction of the aqueous sulfate reduction obey first-order kinetics. The rate constants are strongly dependent on temperature. The temperature dependence of the reaction rate (min-1) is given by the following rate law: log k=-10.3×103/T+15.1. The activation energy for the reaction of sulfate reduction is 208 kJ mol-1. The remaining sulfates display distinct sulfur isotopic variations under a closed system due to the kinetic isotope effect. The kinetic isotope fractionation factor can be expressed as: 103(α-1)=3.32×106/T2-4.19. The kinetic isotope effects during abiogenic reduction of the sulfate may depend on the atomic hydrogen produced, independent of the reducing agents.