An Experimental Study on Early Evolution of the Earth and the Structure of the Lower mantle

我们继续使用配备有烧结金刚石砧的Kawai室在同步加速器Spring-a上进行实验以产生更高的压力。在安德森等人的Au male上，在室温下产生的压力达到85 GPa，在1000 K下达到87 GPa。本文系统地研究了MgGeO_3在74 GPa和1900 K下的Pv-后钙钛矿（PPv）相变。以MgGeO_3钛铁矿+0.1 Au（重量比）的混合物为原料，直接装入一个装有薄W/W-Re热电偶的圆柱形TiB_2加热器中，加热器中心为MgO +0.05Cr_2O_3（重量比）的小八面体压力介质。压力值是从安德森的Au的测量体积以1000秒标度确定的。在63.2GPa和1323 K下首次证实了Pv向PPv的转变。然后，我们试图通过降低压力和保持温度恒定来观察反转反应，直到p <0.05时才发现Pv的生长。 ...更多信息 压力下降到60.5GPa，在62.8GPa和1473 K下，通过加热观察到从反转的Pv到PPv的第二次转变。在下一次实验中，发现结晶良好的Pv在比预期的Pv-PPv相界高得多的压力下持续存在，并且PPv的生长在74 Gpa和1873 K下首次被识别。考虑到缓慢的反应速率，我们在第三次实验中观察到Pv和PPv的生长以及两相的共存。由此确定的相界由等式T（K）= 191.2P（Gpa）-10563表示。如果将本文所得到的MgGeO_3相界dP/dT斜率应用于地幔中的Pv-PPv转变，PPv将被抑制到下地幔底部，不能形成所谓的PPv透镜。为了克服DIA型压力机在挤压Kawai细胞方面的缺点，我们研制了一种新的六轴装置，该装置由高科技伺服机构控制六个砧座的运动。在± 2 μm的精度范围内保持Ka Wai-cell立方是可能的。使用烧结金刚石立方砧的压力产生进行了高达约。60 GPa的GaP，Zr和Fe_2O_3的电阻测量。结果进行了比较与以前的校准在春季8通过原位X射线观测。结果表明，在DIA型压力机中，相当大的载荷与摩擦力相平衡。负荷损失达45%左右.在2000 K和2000 GPa的温度范围内，测量了由（Mg_xFe_（0.1））_2SiO_4组成的水硅铝石和水硅铝石在无水和含水条件下的电导率。在很宽的温度范围内的测量使得有可能确定两种材料的跳跃和质子传导机制的参数。这些结果表明，地幔过渡带（410 ~ 660 km）的地磁测量结果与无水硅铝石和水硅铝石的电导率一致，排除了地幔过渡带的湿态假设。少

We have continued experiments to generate higher pressures using the Kawai-cell equipped with sintered diamond anvils at synchrotron Spring-a The generated pressure reached 85 GPa at room temperature and 87 GPa at 1000 K on the Anderson et a〓s au male Based on these innovations of experimental techniques, we have systematically examined the penovskite (Pv) -postperovskite (PPv) transformation in MgGeO_3 up to 74 GPa and 1900 K. The starting material was a fine mixture of MgGeO_3 ilmenite + 0.1 Au (in weight), which was directly loaded in a cylindrical TiB_2 heater set with a thin W/W-Re thermocouple at the center of a mall octahedral pressure medium of MgO +0.05Cr_2O_3 (in weight). Pressure value was determined form measured volume of Au from the Anderson at a〓s scale. The transformation from Pv to PPv was first confirmed at 63.2 GPa and 1323 K. Then we tried to observe the reversal reaction by decreasing pressure and keeping temperature constant Growth of Pv was not recognized until p … More ressure went down to 60.5 GPa., suggesting the reversal reaction to be fitly sluggish The second transformation to PPv from the reversed Pv was observed at 62.8 GPa and 1473 K by heating. In the next run, it was found that well crystalline Pv persisted to pressures much higher than the expected Pv-PPv phase boundary, and growth of PPv was first recognized at 74 Gpa and 1873 K Taking the slow reaction rate in to consideration, we observed the growth of the Pv and PPv and the coexistence of both the phases in the 3rd nut The run. The phases boundary thus determined is expressed by the equation; T (K) = 191.2P (Gpa) -10563. If dP/dT slope of the phase boundary obtained in the present study for MgGeO_3 were applicable to the Pv-PPv transformation in the mantle, the PPv would be suppressed to the bottom the lower mantle, and on called PPv lens may not form. We have also pointed out that the establishment of reliable pressure scale is urgent issue of high pressure Earth science.In order to overcome faults of the DIA type press in squeezing the Kawai-cell, we have developed a new 6-axis apparatus in which movement of the six anvils are controlled by the high tech servo mechanism. It is possible to keep the Ka wai-cell cubic within accuracy of ± 2 μm. Pressure generation using sintered diamond cubic anvils was carried out up to ca. 60 GPa by measuring electrical resistance of GaP, Zr, and Fe_2O_3. The results are compared with the previous calibration performed at Spring-8 by means of in situ X-ray observation. It is demonstrated that significant amount of applied load is balanced with frictional force in the DIA type press. The load loss amounts to 45 % at ca. 60 Gpa.Electrical conductivity of wadsleyite and ringwoodite with composition of (Mg〓Fe0.1)_2SiO_4 was measured up to 20 Gpa and 2000K under both anhydrous and hydrous conditions. Measurement over the wide temperature range made it possible to determine the parameters for hopping and proton conduction mechanisms for both the materials. These results imply that electrical conductivity of the mantle transition zone (depths from 410 to 660 km) determined by the geomagnetic measurement is well reconciled anhydrous wadsleyite and ringwoodite and hypothesis of wet transition zone is ruled out. Less