HIGH-PRESSURE EXPERIMENTAL STUDIES ON THE ORIGIN OF LAYERED STRUCTURE OF THE EARTH

利用SPring-8同步辐射装置和装有烧结金刚石（SD）的多砧装置（MA），进行了高温高压下的原位X射线研究。在约4立方毫米的空间内产生了49 GPa的压力。利用该系统测定了立方SnO_2（Pa ~（3-））在29 GPa和1500 K范围内的稳定性和热弹性性质，并对铁的第五多晶型“β-Fe”进行了探索。在40 GPa和1700 K下，ε相稳定，没有β-FeSOFA的存在。结果表明，在31 GPa压力下，随着压力的增加，第一液相线相由镁橄榄石（Mw）转变为镁钙钛矿（Mg-Pv）。在高于33 GPa的压力下（地幔深度超过1000 km），Mg-Pv，Mw和Ca-Pv在固相线和液相线之间的温度下与液体共存。质量平衡回归分析表明，橄榄岩物质由34% Mg-Pv和3% Ca-Pv从原始地幔分异而来。Mg-Pv和Ca-Pv的分馏作用在地幔底部形成了一个致密的热区域，具有富集地球化学储集的特征。在29 GPa压力下对Ni、Co在熔融铁和硅酸盐液体之间的分配、Mg-Pv和Mw进行了研究。实验结果表明，在1000 km深的岩浆洋中形成的核与Ni、Co在地幔和核之间的分配数据是一致的。

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 49 GPa were generated over ca 4 mm^3. Using this systems stability and thermoelastic properties of the cubic SnO_2 (Pa3-) were determined up to 29 GPa and 1500 K.Exploration of 5th polymorph of iron "β-Fe" has been carried out. No evidence of β-Fesofar, but ε-phase is stable up to ca 40 GPa and 1700K.Melting experiments on natural peridotite were carried out up to 35 GPa. It has been found that the first liquidus phase changes from magnesiowustite (Mw) to Mg-perovskite (Mg-Pv) at 31 GPa with increase of pressure. At pressures higher than 33 GPa (deeper than 1000 km in the mantle), Mg-Pv, Mw and Ca-Pv coexist with liquid at temperatures between solidus and liquidus. Mass balance regression analysis suggest that differentiation of 34% Mg-Pv and 3% Ca-Pv from the primitive mantle consistently form the peridotitic material. Fractionation of Mg-Pv and Ca-Pv would have formed an dense and hot region on the bottom of the mantle characterized as an enriched geochemical reservoir. 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.