Volcanically modulated pyrite burial and ocean–atmosphere oxidation

Stephanie L. Olson, Chadlin M. Ostrander, Daniel D. Gregory, Moutusi Roy, Ariel Anbar, Timothy W. Lyons

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

It is widely assumed that changes in the rate of biological O2 supply to the atmosphere played little, if any, role in driving the Great Oxidation Event (GOE) because extensive biological O2 production via oxygenic photosynthesis significantly predates atmospheric oxygenation on Earth. Moreover, the C isotope record seemingly precludes a dramatic increase in O2-liberating burial of organic C in the late Archean. However, organic C burial is not the only way in which the biosphere may oxidize the Earth's atmosphere. Biologically mediated burial of reduced mineral phases may also yield net oxidation. For example, reducing power can be transferred from organic matter to H2S via anaerobic respiration and ultimately stored in sedimentary pyrite (FeS2). Changes in pyrite burial may thus impact Earth's oxidation trajectory. Here, we revisit the earliest recognized episode of sulfide-rich (euxinic), pyrite-precipitating conditions in Earth's ocean, ∼200–300 million years prior to the GOE, as preserved in the ∼2.7–2.6 billion-year-old (Ga) Roy Hill Shale of the Jeerinah Formation. Applying Fe speciation and trace metal proxies to drillcore samples from two sites, we characterize both spatial and temporal heterogeneity in the accumulation of H2S in the otherwise Fe-rich Hamersley Basin. We argue that extensive pyrite burial in these locally euxinic environments was the consequence of enhanced volcanic emanations of SO2 to the atmosphere rather than oxidative weathering of crustal sulfides. Because SO2 reduction and burial as pyrite is chemically analogous to CO2 reduction and burial as organic matter, we further posit that this alternative oxidation pathway contributed to Earth's protracted oxygenation during the GOE. Our results thus highlight the need for continued study of the interplay between solid-Earth, volcanic, and biological processes and their joint modulation of oceanic and atmospheric composition.

Original languageEnglish (US)
Pages (from-to)417-427
Number of pages11
JournalEarth and Planetary Science Letters
Volume506
DOIs
StatePublished - Jan 15 2019

Keywords

  • euxinia
  • Great Oxidation Event
  • oxygenic photosynthesis
  • pyrite
  • subaerial volcanism

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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