Oxygen as a light element: A solution to single-stage core formation | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Oxygen as a light element: A solution to single-stage core formation

Type de publication:

Journal Article

Source:

Earth and Planetary Science Letters, Volume 288, Ticket 1-2, p.108-114 (2009)

ISBN:

0012-821X

Numéro d'accès:

ISI:000272788500010

URL:

http://www.sciencedirect.com/science/article/pii/S0012821X09005457

Mots-clés:

UMR 7154 ; Minéralogie ; N° Contribution : 2504 ; planetary differentiation; core; magma ocean; siderophile elements; light element; oxygen

Résumé:

The abundances of siderophile elements in the silicate Earth indicate that Earth's iron-rich core probably formed at high pressure and high temperature. A popular model of core formation considers that the concentrations of several moderately siderophile elements are consistent with a scenario of simple single-stage equilibration at the base of a magma ocean. However, recent work using temperature sensitive partitioning data for V and Nb have casted doubt on this interpretation since the required basal temperature would greatly exceed that of the mantle solidus. Here we show that single-stage core formation event could explain the mantle contents of siderophile elements best constrained by experiment (Ni, Co, V, Mn, Cr, and Nb) provided that the core contains a few weight percents of oxygen. Our calculations, based on partitioning and metallurgy data, reveal that V and Nb become significantly less siderophile with increasing the 0 content of core-forming materials, while the behaviour of Ni, Co, Cr and Mn is little affected. Since the other likely light element candidates C, Si and S do not drastically influence the siderophile behaviour, we conclude that a simple-equilibration scenario is a viable hypothesis only if 0 contributes partially to the core density deficit. This interpretation is consistent with the W budget of the silicate Earth and recently published W metal-silicate partitioning data. The presence of a few weight percents of oxygen in the core is also in agreement with recent high-pressure high-temperature solubility measurements in molten iron equilibrated with perovskite and ferropericlase. (C) 2009 Elsevier B.V. All rights reserved.

Notes:

Corgne, Alexandre Siebert, Julien Badro, James