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

利用SPring-8同步辐射和烧结金刚石（SD）多砧装置（MA），开展了高压高温下的原位x射线研究。在大约4 mm^3的范围内产生了高达49 GPa的压力。用该体系测定了立方SnO_2 （Pa3-）在29gpa和1500k下的稳定性和热弹性。对铁的第五晶型“β-Fe”进行了探索。没有β-Fesofar的证据，但ε-相稳定到约40 GPa和1700K。对天然橄榄岩进行了高达35gpa的熔融实验。在31 GPa时，随着压力的增加，第一液相相由镁武矿（Mw）转变为镁钙钛矿（Mg-Pv）。在压力大于33 GPa（地幔深度大于1000 km）时，Mg-Pv、Mw和Ca-Pv与液体共存，温度介于固液之间。质量平衡回归分析表明，原始地幔中34%的Mg-Pv和3%的Ca-Pv分化一致形成了橄榄岩物质。Mg-Pv和Ca-Pv的分选作用将在地幔底部形成致密热区，其特征为地球化学富集储层。实验结果表明，1000km深岩浆海的岩心形成与观测到的地幔-岩心之间Ni和Co的分配数据一致。

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.