HIGH-PRESSURE EXPERIMENTAL, STUDIES OF DIFFERENTIATION AND LAYERED STRUCTURE OF THE EARTH

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In situ X-ray study at high-pressure and high -temperature has been developed using the synchrotron radiation at SPring-8 and a multi-anvil apparatus MA) equipped with sintered diamond (SD). Pressures to 40 GPa were generated over ca.5mmィイD13ィエD1. Using this systems termoelastic properties of the cubic SnOィイD22ィエD2 (Pa3-) were determined up to 29 GPa and 1500 K. Exploration of iron "β-Fe" has not be successful so far, and ε-phase is stable up to ca.40 GPa and 1700 K.Melting experiments on natural peridotite were carried out to 35 GPa. It was observed that the first liquidus phase changed from magnesiowustite (Mw) to Mg-perovskite (Mg-Pv) at 31 GPa with increase of pressure. Phase differentiation and element partitioning upon melting were clarified based on analyses of the experimental charges. Fractionation of Mg-Pv and Ca-Pv should proceed predominantly in a magma ocean deeper than 1000 km, which may be directly related to the formation of the geochemical reservoir in the lower mantle. Partioning of Ni and Co between molten iron, and silicate liquid, Mg-Pv and Mw were examined up to 29 GPa. The experimental results suggest that core formation in a 1000km-depth magma ocean is consistent with the observed partitioning data of Ni and Co between the mantle and core.