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FeO Content of Earth’s Liquid Core

Pozzo, M; Davies, C; Gubbins, D; Alfè, D; (2019) FeO Content of Earth’s Liquid Core. Physical Review X , 9 (4) , Article 041018. 10.1103/physrevx.9.041018. Green open access

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Abstract

The standard model of Earth’s core evolution has the bulk composition set at formation, with slow cooling beneath a solid mantle providing power for geomagnetic field generation. However, controversy surrounding the incorporation of oxygen, a critical light element, and the rapid cooling rates needed to maintain the early dynamo have called this model into question. The predicted cooling rates imply early core temperatures that far exceed estimates of the lower mantle solidus, suggesting that early core evolution was governed by interaction with a molten lower mantle. Here we develop ab initio techniques to compute the chemical potentials of arbitrary solutes in solution and use them to calculate oxygen partitioning between liquid Fe-O metal and silicate melts at the pressure-temperature (P-T) conditions expected for the early core-mantle system. Our distribution coefficients are compatible with those obtained by extrapolating experimental data at lower P-T values and reveal that oxygen strongly partitions into metal at core conditions via an exothermic reaction. Our results suggest that the bulk of Earth’s core was undersaturated in oxygen compared to the FeO content of the magma ocean during the latter stages of its formation, implying the early creation of a stably stratified oxygen-enriched layer below the core-mantle boundary (CMB). FeO partitioning is accompanied by heat release due to the exothermic reaction. If the reaction occurred at the CMB, this heat sink could have significantly reduced the heat flow driving the core convection and magnetic field generation.

Type: Article
Title: FeO Content of Earth’s Liquid Core
Open access status: An open access version is available from UCL Discovery
DOI: 10.1103/physrevx.9.041018
Publisher version: https://doi.org/10.1103/physrevx.9.041018
Language: English
Additional information: Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license https://creativecommons.org/licenses/by/4.0/
Keywords: Chemical Physics, Geophysics, Statistical Physics
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10084532
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