Pathways for Neoarchean pyrite formation constrained by mass-independent sulfur isotopes

James Farquhar*, John Cliff, Aubrey L. Zerkle, Alexey Kamyshny, Simon W. Poulton, Mark Claire, David Adams, Brian Harms

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

119 Scopus citations

Abstract

It is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the Neoarchean. It is puzzling, therefore, that the sulfur isotope record of the Neoarchean is characterized by a signal of atmospheric massindependent chemistry rather than a strong overprint by sulfate reducers. Here, we present a study of the four sulfur isotopes obtained using secondary ion MS that seeks to reconcile a number of features seen in the Neoarchean sulfur isotope record. We suggest that Neoarchean ocean basins had two coexisting, significantly sized sulfur pools and that the pathways forming pyrite precursors played an important role in establishing howthe isotopic characteristics of each of these pools was transferred to the sedimentary rock record. One of these pools is suggested to be a soluble (sulfate) pool, and the other pool (atmospherically derived elemental sulfur) is suggested to be largely insoluble and unreactive until it reacts with hydrogen sulfide. We suggest that the relative contributions of these pools to the formation of pyrite depend on both the accumulation of the insoluble pool and the rate of sulfide production in the pyrite-forming environments. We also suggest that the existence of a significant nonsulfate pool of reactive sulfur has masked isotopic evidence for the widespread activity of sulfate reducers in the rock record.

Original languageAmerican English
Pages (from-to)17638-17643
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number44
DOIs
StatePublished - 29 Oct 2013
Externally publishedYes

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