Guided by chemical thermodynamics, all available metal-silicate partition coefficients for Ni, Co, P, Mo and W (M) are regressed against 1/T, P/T, lnfO2, ln(1-XS) (XS = mole fraction of sulfur in metallic liquid) and nbo/t (a silicate melt structural parameter) to derive equations of the form, lnD(M) = a lnfO2 + b/T + cP/T + dln(1-XS) + e(nbo/t) + f, that can be used to predict D(M) as a function of these intensive parameters. Such expressions are derived for both sulfur-free and sulfur-bearing systems, for solid metal-liquid silicate and liquid metal-liquid silicate. We investigate whether Earth's upper mantle siderophile element abundances can be reconciled with simple metal-silicate equilibrium in the mantle. Sulfur-free metallic compositions do
not allow a good fit. However, Ni, Co, W and P abundances in the upper mantle are consistent with simple metal-silicate equilibrium at elevated pressures (30.0 GPa, 2125 šC, DIW = -0.3), in a sulfur-bearing system. Although this P-T point is near the anhydrous peridotite solidus, it is well above the hydrous solidus and most likely closer to the liquidus. A hydrous magma ocean and early mantle is consistent with predicted atmospheric evolution models.