Multiple Sulfur Isotope Evidence for Bacterial Sulfate Reduction and Sulfate Disproportionation Operated in Mesoarchaean Rocks of the Karelian Craton

• Published in: Minerals
• Main Authors: Sergey V. Vysotskiy, Tatyana A. Velivetskaya, Aleksandr V. Ignatiev, Aleksandr I. Slabunov, Anna V. Aseeva
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2022
• Subjects: Mesoarchean; multiple sulfur isotopes; bacterial sulfate reduction; sulfur disproportionation; Mineralogy; QE351-399.2; karelian
• Online Access: https://doi.org/10.3390/min12091143; https://doaj.org/article/df393b449d4d41a18007f0cda655442d

Sulfur isotope in sulfides from the Paleoarchean and the Neoarchean sedimentary rocks evidence microbial sulfur metabolism in Archean sulfur cycle. However, sulfur metabolism for the Mesoarchean interval is less obvious since evidence for a large range in sulfur isotope values has not yet been observed in Mesoarchean samples. We report the results of multiple sulfur isotope measurements for sulfide minerals from ~2.8 Ga sedimentary rocks in the southeastern part of the Karelian Craton. In situ isotope analysis of sulfide grains have been performed using a femtosecond laser-ablation fluorination method. Sulfide samples studied here yielded Δ 33 S values between −0.3 and +2.7‰ and δ 34 S values between −10 and +33‰. The Δ 33 S dataset was interpreted to indicate the incorporation of sulfur from two coexisting sulfur pools, photolytic sulfate and photolytically derived elemental sulfur. We suggest that the relative contributions of these Δ 33 S different pools to the pyritic sulfur could be controlled by the metabolic activity of coexisting sulfate-reducing and sulfur-disproportionating bacteria during pyrite formation. We therefore suggest the operation of different metabolic pathways of sulfur in Mesoarchean sedimentary environments.