MOBILITY OF CORE MELTS DURING EARTHS ACCRETION

We have equilibrated carbon-saturated Fe-Ni-Co-S melts in a San-Carlos olivine matrix between 1350 and 1570 degrees C at 2 GPa, to measure t he median dihedral angles of metallic core melts in a silicate mantle matrix as a function of temperature and Sulfur fugacity. The angles in crease from about 68 degrees for the most oxidized monosulfide liquid solutions (metal-sulfur ratio similar to 0.97), to similar to 115 degr ees for the most reduced metal-rich melts (M/S similar to 100), Temper ature effects are small, These angles preclude that metallic core melt s could have segregated efficiently from a crystalline silicate mantle by grain boundary percolation, We suggest that core formation must ha ve occurred from a magma ocean.