EXPERIMENTAL DETERMINATION OF METAL/SILICATE PARTITION COEFFICIENTS FOR P, CO, NI, CU, GA, GE, MO, AND W AND SOME IMPLICATIONS FOR THE EARLY EVOLUTION OF THE EARTH

Abstract

Metal/silicate partition coefficients were determined at 1600°C for P, Ga, Ge and W and at 1300°C for P, Fe, Co, Ni, Cu, Ga, Ge, Mo and W. Experiments span a range of two orders-of-magnitude in oxygen fugacity. Good correlations between logƒO2 and the log of the partition coefficients were observed for all elements. The slopes of these correlations reflect the number of oxygen atoms associated with the metal oxides in the silicate phase. The composition of the silicates was basaltic, but variable with respect to FeO; from about 4% FeO at the most reducing experiments to 45% FeO at the most oxidizing experiments. Within these variations no dependence of the partition coefficients on silicate composition was observed, except for Ni and Co. The unusual slopes in the log DNi and log DCovs. logƒO2 correlations can be explained by a strong dependence of the NiO and CoO activities on the liquid silicate composition.