Experimental Studies on Chemical Structure of the Deep Mantle and Its formation Processes.

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Experimental studies on the earth matrials have been performed using the multi-anvil type high pressure apparatus with the following results during the term of project.1. Phase relations among the mantle minerals above 8 GPa : Phase equilibrium diagrams have been determined for the system (1) forstbrite-anorthite-diopside, (2) diopside-enstatite, and (3) forsterite-pyrope. Pressure dependence of the composition of the liquid produced by partial melting and the melting behavior of the minerals present were elucidated.2. Transitions and phase equilibria of the core materials : (1) Transitions of Fe were determined by the electric resistance method developed in our laboratory. (2) Phase equilibria of the system Fe-Fes were determined at 8 GPa.3. Partitioning of elements between core and mantle materials : Partitioning of some elements between mantle minerals, silicate melts, and metal iron above 10 GPa was determined, and the relationships between abundance of these elements and core-mantle equilibrium odel were examined on the basis of the experimental data.4. In-situ observation of MgSiO_3 transition by X-ray diffraction analysis : Transition of clinopyroxene structure - Mg_2SiO_4 spinel +stishovite - ilmenite structure were determined at 20 - 27 GPa.5. Martian Interior model ; High pressure-high temperature experiments were carried out on a estimated martian mantle composition and a structure model of the martian interior were presented, based on the experimental results.6. Density of peridotite melt at high pressures : Pressure dependence of forsterite and peridotite melt were examined with the result suggesting that density cross over between forsterite and Fe-rich peridotite melt is not probable.