Element partitioning constraints on the light element composition of the Earth's core

摘要

Partitioning of sulfur (S), oxygen (O) and silicon (Si) between liquid Fe-Ni-alloy (LA) and liquid silicate (LS) was studied with a multi-anvil apparatus at pressures between 2 and 25 GPa and temperatures between 2073 and 2623 K. We found that S has a strong affinity for liquid Fe-Ni-alloy at all the experimental conditions investigated. Partition coefficient of S between liquid Fe-Ni-alloy and liquid silicate( D-S(LMS)) increases with pressure and decreases with temperature. At the proposed pressure and temperature of core-mantle equilibrium during early Earth differentiation [Li and Agee, 1996; Righter et al., 1997], S is highly siderophile ( D-S(LMS) similar to 1000), while Si and O are highly lithophile (D-Si(LMS), D-o(LMS) < 0.03). Our study suggests that if the core composition was largely established by equilibrium partitioning in a deep magma ocean, then S is the most plausible principle light element in the core. [References: 21]