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Ferrous iron partitioning in the lower mantle

Muir, JMR; Brodholt, JP; (2016) Ferrous iron partitioning in the lower mantle. Physics of the Earth and Planetary Interiors , 257 (C) pp. 12-17. 10.1016/j.pepi.2016.05.008. Green open access

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Abstract

We used density functional theory (DFT) to examine the partitioning of ferrous iron between periclase and bridgmanite under lower mantle conditions. To study the effects of the three major variables — pressure, temperature and concentration — these have been varied from 0 to 150 GPa, from 1000 to 4000 K and from 0 to 100% total iron content. We find that increasing temperature increases KD, increasing iron concentration decreases KD, while pressure can both increase and decrease KD. We find that KD decreases slowly from about 0.32 to 0.06 with depth under lower mantle conditions. We also find that KD increases sharply to 0.15 in the very lowermost mantle due to the strong temperature increases near the CMB. Spin transitions have a large effect on the activity of ferropericlase which causes KD to vary with pressure in a peak-like fashion. Despite the apparently large changes in KD through the mantle, this actually results in relatively small changes in total iron content in the two phases, with View the MathML sourceXFefp ranging from about 0.20 to 0.35, before decreasing again to about 0.28 at the CMB, and View the MathML sourceXFebd has a pretty constant value of about 0.04–0.07 throughout the lower mantle. For the very high Fe concentrations suggested for ULVZs, Fe partitions very strongly into ferropericlase.

Type: Article
Title: Ferrous iron partitioning in the lower mantle
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.pepi.2016.05.008
Publisher version: http://dx.doi.org/10.1016/j.pepi.2016.05.008
Language: English
Additional information: © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
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/1508348
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