Anomalous fractionations of sulfur isotopes during thermochemical sulfate reduction

Yumiko Watanabe, James Farquhar, Hiroshi Ohmoto

Research output: Contribution to journalArticlepeer-review

128 Citations (Scopus)


Anomalously fractionated sulfur isotopes in many sedimentary rocks older than 2.4 billion years have been widely believed to be the products of ultraviolet photolysis of volcanic sulfur dioxide in an anoxic atmosphere. Our laboratory experiments have revealed that reduced-sulfur species produced by reactions between powders of amino acids and sulfate at 150° to 200°C possess anomalously fractionated sulfur isotopes: Δ33 = +0.1 to +2.1 per mil and Δ36 = -1.1 to +1.1 per mil. These results suggest that reactions between organic matter in sediments and sulfate-rich hydrothermal solutions may have produced anomalous sulfur isotope signatures in some sedimentary rocks. If so, the sulfur isotope record of sedimentary rocks may be linked to the biological and thermal evolution of Earth in ways different than previously thought.

Original languageEnglish
Pages (from-to)370-373
Number of pages4
Issue number5925
Publication statusPublished - 2009 Apr 17


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