High Pressure Phase Transformations Down to the Lower Mantle Conditions and Implications for the Nature of the Seismic Discontinuities.

采用淬火法和原位X射线衍射法对地幔材料进行了高温高压实验。在压力为28 GPa和温度为沿着典型地幔地温的条件下，用前一种方法研究了地幔岩组成中的相变，结果表明，共存相中铁的分配对橄榄石的改性尖晶石相和尖晶石相之间的压力区间宽度有显著影响，这与最近地震学研究所揭示的410 km不连续性的性质是一致的。另一方面，我们提出了一些数据的铁之间的钙钛矿和镁橄榄石下地幔条件下的分配，并表明，铁的分配系数接近统一的压力增加的结果，铝在钙钛矿相。在此基础上讨论了660 km地震波的尖锐性，并利用同步辐射源（SPring-8）和多砧装置的现场X射线测量确定了尖晶石相和后尖晶石相之间的相界。边界确定在温度高达约2000摄氏度，表明后尖晶石相边界具有负克拉珀龙斜率估计淬火实验和热力学分析。边界位于约21 GPa，1600 ° C，比先前基于其他高压研究的估计低约2 GPa。

High pressure and high temperature experiments have been made on mantle materials using both quench method and in situ X-ray diffraction measurement. The phase transformations in a pyrolite composition were studied by the former method at pressures to 28 GPa and temperatures along a representative mantle geotherm.It was demonstrated that iron partitioning of the coexisting phases in this composition affects significantly the width of the pressure interval between the modified spinel and spinel phases of olivine, which is consistent with the nature of the 410km discontinuity revealed by the recent seismological studies. On the other hand, we presented some data on the partitioning of iron between perovskite and magnesiowustite under the lower mantle conditions, and showed that the iron partition coefficient approaches unity with increasing pressure as a result of the increase of aluminum in the perovskite phase. The sharpness of the 660km seismic is discussed on the basis of these experimental data.The phase boundary between spinel and the postspinel phase has been determined by in situ X-ray measurements using a combination of the synchrotron source (SPring-8) and a multianvil device. The boundary was determined at temperatures up to about 2000ﾟC,demonstrating that the postspinel phase boundary has a negative Clapeyron slope as estimated by quench experiments and thermodynamic analyzes. The boundary was located at about 21 GPa, at 1600ﾟC,which is about 2GPa lower than the earlier estimations based on other high pressure studies.