Sulfur Cycling During Progressive Burial in Sulfate‐Rich Marine Carbonates

Jiang, Lei, Fakhraee, Mojtaba, Cai, Chunfang and Worden, Richard H ORCID: 0000-0002-4686-9428
(2020) Sulfur Cycling During Progressive Burial in Sulfate‐Rich Marine Carbonates. Geochemistry, Geophysics, Geosystems, 21 (12).

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<jats:title>Abstract</jats:title><jats:p>The isotopic composition of sulfate in the rock record has been frequently used to track the changes in the Earth's surface environments. By considering isotopic fractionation imparted by microbial sulfate reduction (MSR) and thermochemical sulfate reduction (TSR), in this study, we aim to develop a holistic understanding of the mixed effects of MSR and TSR on δ<jats:sup>34</jats:sup>S signals in sulfate‐rich carbonate systems. We report the occurrence of various types of sulfur‐bearing components from the Cambrian‐Ordovician carbonate system in the Tarim Basin, NW China, coupled with a well‐established diagenesis framework for these rocks. Our results indicate that most of the sulfur‐bearing species possess δ<jats:sup>34</jats:sup>S values slightly lower than both the source sulfate and the sulfide generated by TSR, yet these sulfur‐bearing species have substantially higher δ<jats:sup>34</jats:sup>S values than sulfide that resulted from MSR. Hence, a combination of sulfides sourced from MSR and TSR can adequately explain the sulfur isotope data in the studied interval. Building upon this hypothesis, we developed a new sulfur diagenesis model in order to quantify the accumulated H<jats:sub>2</jats:sub>S from the combined effects of MSR and TSR. Our new model can be used to explain the origin of sulfur‐bearing species in many other deep burial carbonate systems, including the Sichuan Basin, China, and the Gulf of Mexico, USA. We propose that greater attention should be paid to isotopic modulation through mixed diagenetic processes in order to gain a better mechanistic understanding of the primary geochemistry signals (e.g., δ<jats:sup>34</jats:sup>S) in marine carbonates.</jats:p>

Item Type: Article
Uncontrolled Keywords: 0454, 0471, 0488, 1051, 3675, carbonate, diagenesis, microbial sulfate reduction, sulfur cycling, sulfur isotope, thermochemical sulfate reduction
Depositing User: Symplectic Admin
Date Deposited: 08 Dec 2020 08:26
Last Modified: 04 Sep 2023 19:24
DOI: 10.1029/2020gc009383
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