Sulfur and mercury MIF suggest volcanic contributions to Earth’s atmosphere at 2.7 Ga
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The Archean eon is associated with large-scale changes in Earth’s geosphere and biosphere, including the onset of plate tectonics and the expansion of oxygenic photosynthesis, although the full impacts of these changes on the atmosphere remain unclear. Here we present coupled records of mass independent fractionation of sulfur (S-MIF) and mercury (Hg-MIF) isotopes from well preserved sediments of the ∼2.7 billion year old (Ga) Manjeri Formation, Belingwe Greenstone Belt, Zimbabwe. These palaeoatmospheric proxies record different trends for S-MIF and odd number Hg-MIF versus even number Hg-MIF, providing novel constraints on atmospheric chemistry during this time. S-MIF and odd number Hg-MIF values are muted in comparison to values preserved in later Archean sediments, representing a combination of enhanced volcanic input and local mixing. Even number Hg-MIF is absent from these sediments, consistent with complete photo-oxidation of gaseous Hg0, which could have been driven by increased halogen emissions from arc volcanism. When considered within a global geodynamic context, these MIF data suggest an important role for subduction zone-related volcanism associated with early plate tectonics in modulating the ∼2.7 Ga atmosphere.
Zerkle , A L , Claire , M , Di Rocco , T , Grassineau , N , Nisbet , E , Sun , R & Yin , R 2021 , ' Sulfur and mercury MIF suggest volcanic contributions to Earth’s atmosphere at 2.7 Ga ' , Geochemical Perspectives Letters , vol. 18 , pp. 48-52 . https://doi.org/10.7185/geochemlet.2124
Geochemical Perspectives Letters
Copyright © 2021 The Authors. Open Access article. Published by the European Association of Geochemistry under Creative Commons License CC BY-NC-ND 4.0.
DescriptionThis study received funding from a Natural Environment Research Council Standard Grant NE/M001156/1 (ALZ, EGN), and from the European Research Council under the European Union’s Horizon 2020 research and innovation programme (Grant 678812 to MWC).
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