Metal/silicate equilibrium in the early Earth - New constraints from the volatile moderately siderophile elements Ga, Cu, P, and Sn

We report new measurements of metal/silicate partition coefficients for Ga, Cu, and Sn at 10 to 90 kb and 1250 to 1900 degrees C. We show that all thr ee of these siderophile elements (D(metal/silicate) > 10) become more litho phile at high pressure and temperature conditions. Metal/silicate partition coefficients calculated for the conditions of an early deep magma ocean ar e all close to or less than 1. Thus, in an early terrestrial magma ocean sc enario, the depletions of these elements in the mantle must be caused by vo latility rather than by metal/silicate equilibrium. For Mars, moderate mant le depletions of both Sn and Cu (relative to Earth) may be due to separatio n of an S-rich metallic core. In contrast, the sizable depletions of Ga in the Moon and Vesta must be caused by both volatility and core formation. Vo latility controlled depletions of these elements may have been inherited fr om early solar system materials. Copyright (C) 2000 Elsevier Science Ltd.