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Modelling of Equilibrium Between Mantle and Core: Refractory, Volatile, and Highly Siderophile Elements
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Author and Affiliation:
Righter, K.(NASA Johnson Space Center, Houston, TX, United States);
Danielson, L.(Jacobs Technologies Engineering Science Contract Group, Houston, TX, United States);
Pando, K.(Hamilton Sundstrand Corp., Engineering Science and Contract Group, Houston, TX, United States);
Shofner, G.(Institut de Physique du Globe, Paris, France);
Lee, C. -T.(Rice Univ., Dept. of Earth Sciences, Houston, TX, United States)
Abstract: Siderophile elements have been used to constrain conditions of core formation and differentiation for the Earth, Mars and other differentiated bodies [1]. Recent models for the Earth have concluded that the mantle and core did not fully equilibrate and the siderophile element contents of the mantle can only be explained under conditions where the oxygen fugacity changes from low to high during accretion and the mantle and core do not fully equilibrate [2,3]. However these conclusions go against several physical and chemical constraints. First, calculations suggest that even with the composition of accreting material changing from reduced to oxidized over time, the fO2 defined by metal-silicate equilibrium does not change substantially, only by approximately 1 logfO2 unit [4]. An increase of more than 2 logfO2 units in mantle oxidation are required in models of [2,3]. Secondly, calculations also show that metallic impacting material will become deformed and sheared during accretion to a large body, such that it becomes emulsified to a fine scale that allows equilibrium at nearly all conditions except for possibly the length scale for giant impacts [5] (contrary to conclusions of [6]). Using new data for D(Mo) metal/silicate at high pressures, together with updated partitioning expressions for many other elements, we will show that metal-silicate equilibrium across a long span of Earth s accretion history may explain the concentrations of many siderophile elements in Earth's mantle. The modeling includes refractory elements Ni, Co, Mo, and W, as well as highly siderophile elements Au, Pd and Pt, and volatile elements Cd, In, Bi, Sb, Ge and As.
Publication Date: Jan 01, 2013
Document ID:
20130010073
(Acquired Feb 26, 2013)
Subject Category: GEOPHYSICS
Report/Patent Number: JSC-CN-27949
Document Type: Conference Paper
Meeting Information: Lunar and Planetary Science Conference; 18-22 Mar. 2013; The Woodlands, TX; United States
Meeting Sponsor: Lunar and Planetary Inst.; Houston, TX, United States
Financial Sponsor: NASA Johnson Space Center; Houston, TX, United States
Organization Source: NASA Johnson Space Center; Houston, TX, United States
Description: 2p; In English; Original contains color illustrations
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright; Distribution as joint owner in the copyright
NASA Terms: DEFORMATION; EARTH MANTLE; HIGH PRESSURE; OXIDATION; REFRACTORIES; SIDEROPHILE ELEMENTS; SILICATES
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