Moussallam, Yves;
Georgeais, Guillaume;
Rose‐Koga, Estelle F;
Koga, Kenneth T;
Hartley, Margaret E;
Scaillet, Bruno;
Oppenheimer, Clive;
(2023)
CO_{2}-Undersaturated Melt Inclusions From the South West Indian Ridge Record Surprisingly Uniform Redox Conditions.
Geochemistry, Geophysics, Geosystems
, 24
(12)
, Article e2023GC011235. 10.1029/2023gc011235.
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Abstract
The behavior of Fe3+ during mantle partial melting strongly influences the oxidation state of the resulting magmas, with implications for the evolution of the atmosphere's oxidation state. Here, we challenge a prevailing view that low-degree partial melts are more oxidized due to the incompatible behavior of Fe3+. Our study is based on measurements of Fe3+/∑Fe along with major, minor, trace and volatile elements in olivine- and plagioclase-hosted melt inclusions of CO2 undersaturated mantle melts in South West Indian Ridge lava. These inclusions record minimum entrapment pressures equivalent to depths up to 10 km below the seafloor, record magma ascent rates of 0.03–0.19 m/s, and display exceptionally high CO2/Ba, CO2/Rb, and CO2/Nb ratios, indicative of a CO2-rich mantle source. Accounting for fractional crystallization, we find a uniform melt oxidation state (with an Fe3+/ΣFe at 0.140 ± 0.005 at MgO = 10 wt.%) that displays no systematic variation with major, minor, volatile or trace element contents, thus providing no evidence for a relationship between the degree of partial melting and Fe3+/ΣFe. This can be explained by efficient buffering of Fe3+/∑Fe and fO2 of mid-ocean ridge basalt melts by their surrounding mantle and/or a decrease in the bulk peridotite-melt Fe2O3 partition coefficient with increasing partial melting. We conclude that changes in the Earth's upper mantle temperature over geological time need not have affected the oxidation state of volcanic products or of the atmosphere.
| Type: | Article |
|---|---|
| Title: | CO_{2}-Undersaturated Melt Inclusions From the South West Indian Ridge Record Surprisingly Uniform Redox Conditions |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2023gc011235 |
| Publisher version: | http://dx.doi.org/10.1029/2023gc011235 |
| Language: | English |
| Additional information: | © 2023 The Authors. Geochemistry, Geophysics, Geosystems published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License (http://creativecommons.org/licenses/by-nc-nd/4.0/). |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10184174 |
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