Element Partitioning Between Magnesiowuestite and Silicate Melt as a Function of Melt Composition and Temperature at High Pressure.

The influence of melt composition and temperature on the partitioning of siderophile elements between magnesiowustite (Mw) and silicate melt (Sil) has been studied systematically at 9 GPa. Additional experiments at pressures above 20 GPa were performed to determine the effect of pressure. The determined partition coefficients (KD (M/Mg) Mw/Sil) of M = Fe, Ni, Co, Mn, Cr and V show systematic variation as a function of temperature, pressure and melt composition. Comparison to literature data indicates that variables other than those investigated, for example magnesiowüstite composition may be responsible for the large differences reported for Mw-silicate liquid partitioning. According to the present results magnesiowüstite fractionation can bc cxcluded to contribute significantly to the depletion of the observed elements in the mantle.