Atmosphere-ocean-lithosphere interactions during the Great Oxidation Event: insights from zircon δ18O
Abstract
The Great Oxidation Event (GOE) records a precipitous atmospheric oxygen rise, perhaps by as much as three to four orders of magnitude within a few million years. The timescale of the GOE is primarily constrained by the rapid loss of mass-independently fractionated sulfur isotopes. The drastic surface changes associated with the GOE are reflected by the appearance of marine sulfate and manganese deposits, as well as increased redox-sensitive trace metal abundances in banded iron formations and shale. Each of these manifestations is recorded at the atmosphere-lithosphere or atmosphere-ocean interface. However, how the GOE affected the lithosphere beyond the atmosphere interface has received little attention to date. We present zircon δ18O data from Paleoproterozoic sedimentary successions in Western Australia and Canada that display a step-change from the <7.5‰ Archean background to 9-11‰ by 2.35 Ga. Intriguingly, the timing of this shift coincides with the timing of the GOE. As the subduction process has been shown to be a pre-existing condition to the GOE and the timing of this shift does not correspond to any known periods of enhanced supracrustal tectonic reworking (i.e. the Siderian tectonic `slowdown'), we propose this shift must be explained by the appearance of an isotopically distinct reservoir with high δ18O that was incorporated into subduction zone magmas. One likely candidate is marine sulfate evaporite deposits, which appear with the GOE. The incorporation of this enriched δ18O reservoir would have facilitated the step change seen in the zircon δ18O record. This signal may also be present to a much lower degree associated with the "whiffs" of atmospheric oxygen prior to the GOE.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.T53C..08S
- Keywords:
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- 1645 Solid Earth;
- GLOBAL CHANGEDE: 8110 Continental tectonics: general;
- TECTONOPHYSICSDE: 8157 Plate motions: past;
- TECTONOPHYSICSDE: 8178 Tectonics and magmatism;
- TECTONOPHYSICS