Element partitioning between minearls and silicate melt under high pressure and its implications for the evolution of the terrestrial planets

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High pressure melting experiments on primitive mantle composition material (PM1), thoreiitic basalt (JB2) and Cr-diopside (CD1) were performed from 3 to 23.5 Gpa, and high pressure mineral/silicate melt partition coefficients, D, were measured for major and trace elements. Chemical analysis of major elements was carried out with and Electron Prove Micro Analyzer, and concentrations of trace elements were measured by Secondary Ion Mass Spectrometer. From the time study experiments of PM1 at 15GPa, it was found that at least one hour is required to achieve equilibrium condition between majorite and coexisting silicate melt. In the case of PM1, D of Majorite/silicate melt and Mg-perovskite/silicate melt were measured. D of Garnet, Clino-pyroxene and Ca-perovskite/silicate melt were also measured by using JB2 and CD1.In most of the observed high pressure minerals, D-value was remarkably decreased when the ionic radius of the elements become larger than 90 pm.Therefore, the elements whose ionic radius are larger than 90 pm will concentrate in silicate melt. However, Ca-perovskite/silicate melt system showed different partitioning behavior: Ca-perovskite can accommodate the elements whose ionic radius are 90-110 pm, and the elements with ionic radius of 60 - 80 pm are concentrated in silicate melt. It was also observed that DィイD2NaィエD2. Was obviously increased with increase in pressure. Although this behavior of DィイD2NaィエD2. May be explained by substitution process, this observation can be explained by relative shrinkage of NaィイD1+ィエD1 ion. If NaィイD1+ィエD1 relatively decrease in size for 3%, the observed change in DィイD2NaィエD2 can be explained.