ELEMENT PARTITIONING BETWEEN METALLIC LIQUID, MAGNESIOWUSTITE, AND SILICATE LIQUID AT 20 GPA AND 2500-DEGREES-C - A SECONDARY-ION MASS-SPECTROMETRIC STUDY

We determined the partition coefficients of 20 elements between metall ic liquid, magnsesiowustite, and silicate liquid at 20 GPa and 2500 de grees C. The partition coefficients of V, Cr, Mn, Co, Ni, and Cu betwe en metallic liquid and magnesiowustite are similar to those between me tallic liquid and silicate liquid. The partitioning behavior of Si, P, W and Pb between metallic liquid and magnesiowustite show remarkable differences to that between metallic liquid and silicate liquid, refle cting incompatibility of these elements in magnesiowustite. Comparison of the present data with the previous ones implies that the metallic liquid-siicate liquid partition coefficients of Co, Ni, W, and Mo decr ease whereas those of Cr, and Mn increase due to the combined effect o f pressure and temperature, although some other factors such as the li quid composition might play some roles on a large difference in D for Mo and W. The core and mantle concentrations for Co and Ni estimated b y Allegre et al. [1995] are consistent with the metal-silicate equilib rium at lower mantle conditions, although other models such as inhomog eneous accretion are also able to explain the core-mantle concentratio ns.