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

摘要

We determined the partition coefficients of 20 elements between metallic liquid, magnsesiowustite, and silicate liquid at 20 GPa and 2500 degrees C. The partition coefficients of V, Cr, Mn, Co, Ni, and Cu between metallic liquid and magnesiowustite are similar to those between metallic 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, reflecting 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 decrease whereas those of Cr, and Mn increase due to the combined effect of pressure and temperature, although some other factors such as the liquid 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 by Allegre et al. [1995] are consistent with the metal-silicate equilibrium at lower mantle conditions, although other models such as inhomogeneous accretion are also able to explain the core-mantle concentrations. [References: 12]