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Oxidative elemental cycling under the low O2 Eoarchean atmosphere
Frei, Robert Crowe, Sean A. Bau, Michael Polat, Ali Fowle, David A. Dossing, Lasse N.
Frei, Robert
Crowe, Sean A.
Bau, Michael
Polat, Ali
Fowle, David A.
Dossing, Lasse N.
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Abstract
The Great Oxidation Event signals the first large-scale oxygenation of the atmosphere roughly 2.4 Gyr ago. Geochemical signals diagnostic of oxidative weathering, however, extend as far back as 3.3–2.9 Gyr ago. 3.8–3.7 Gyr old rocks from Isua, Greenland stand as a deep time outpost, recording information on Earth’s earliest surface chemistry and the low oxygen primordial biosphere. Here we find fractionated Cr isotopes, relative to the igneous silicate Earth reservoir, in metamorphosed banded iron formations (BIFs) from Isua that indicate oxidative Cr cycling 3.8–3.7 Gyr ago. Elevated U/Th ratios in these BIFs relative to the contemporary crust, also signal oxidative mobilization of U. We suggest that reactive oxygen species were present in the Eoarchean surface environment, under a very low oxygen atmosphere, inducing oxidative elemental cycling during the deposition of the Isua BIFs and possibly supporting early aerobic biology.
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2016-02-01
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Nature Publishing Group
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Oxidative elemental cycling under the low O2 Eoarchean atmosphere
Robert Frei, Sean A. Crowe, Michael Bau, Ali Polat, David A. Fowle, Lasse N. Døssing
Sci Rep. 2016; 6: 21058. Published online 2016 February 11. doi: 10.1038/srep21058