Quantifying the effect of solid phase composition and structure on solid-liquid partitioning of siderophile and chalcophile elements in the iron-sulfur system

We report experimentally determined partition coefficients between solid and liquid phases for bulk compositions on either side of the Fe-FeS eutectic for a suite of siderophile, chalcophile, and lithophile elements. Experiments were performed at conditions of 1.5 and 2. GPa in pressure ( P), 1323. K in temperature ( T), and virtually identical eutectic sulfide liquid compositions in equilibrium with either solid face centered cubic Fe or solid FeS. This enabled isolation of the effect of solid phase composition and structure from pressure-temperature-melt composition effects. Solid phase-liquid metal partition coefficients ( D values) for Ge, Re, Ni, Co, Cr, Mn, V, Sn, Pb, Re and W differ significantly if partitioning occurs between identical metallic liquids but different solid phases, whereas Zn, Cu and Mo are virtually unaffected. For all elements except Ge and Sn, measured solid Fe-liquid sulfide partition coefficients at 1.5 and 2. GPa are inconsistent with model predictions based on atmospheric pressure experiments, indicating that such models may not be appropriate for modeling core crystallization processes at non-ambient pressure.The framework of a lattice strain-based model of solid-liquid metal partitioning (Stewart et al., 2009) enables us to quantify the effect of the solid phase. Changing the solid phase from Fe to FeS leads to systematic increases in r