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

在此基础上，我们系统地研究了〓GeO_3中钙钛矿(PV)-后钙钛矿型钙钛矿(PPV)的转变。它被直接装载在圆柱形TiB_2加热器中，该加热器位于小型八面体加压介质(重量为MgO+0.05Cr2O_3)的中心。压力值是由〓S标度的安德森金的测量体积确定的。在63.2 Gpa和1323K下，我们首次证实了PV向PPV的转变，然后我们试图通过降压和恒温来观察这一逆转反应。直到p…才发现PV的增长。在62.8 Gpa和1473K下观察到了PPV的第二次转变。在下一次实验中，我们发现结晶良好的PV在比预期的PV-PPV相界更高的压力下持续存在，并且PPV的生长在74 Gpa和1873K首次被识别出来，考虑到慢反应速率，我们在第三次实验中观察到了PV和PPV的生长以及两相的共存。由此确定的相界用公式T(K)=191.2P(Gpa)-10563表示。如果本研究得到的MgGeO_3相界面的dp/dt斜率适用于地幔中的PV-PPV转变，则PPV将被压制到下地幔的底部，而不会形成所谓的PPV透镜。为了克服DIA型压力机挤压川井槽的缺点，我们研制了一种新型的六轴联动装置，该装置由高科技的伺服机构控制六个锤头的运动。用烧结金刚石立方锤通过测量GaP、Zr和Fe_2O_3的电阻，实现了高达60 Gpa的压力产生。结果与先前在Spring8进行的X射线原位观测定标结果进行了比较。结果表明，在DIA型压力机中，相当大的载荷与摩擦力是平衡的。在约60 GPa时，负载损失达45%。在无水和有水条件下，测量了组成为(Mg〓Fe0.1)_2SiO_4的Wadsleyite和Ringwood ite的电导率，分别达到20 GPa和2000K。在宽温度范围内的测量使确定这两种材料的跳跃和质子传导机制的参数成为可能。这些结果表明，地磁测量确定的地幔过渡带(深度为410~660 km)的电导率与无水黄铁矿和环杉石具有很好的一致性，排除了湿过渡带的假说。较少

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