Material investigation on Core-Mantle Boundary

本研究利用改进的双面激光加热金刚石砧池（LHDAC）研究了一些主要地幔矿物在高压和高温下的性质。本研究的结果如下：我们在东北大学新开发了一套激光加热系统，可以在压力下稳定地加热更大的样品。将其技术要点反馈到光子工厂和SPring-8中使用LHDAC构建原位x射线衍射系统中。(2)在30 ~ 60gpa的压力范围内考察了铁与硅酸盐钙钛矿的反应。在30gpa激光加热后的回收样品中发现了产生硅化铁的可能性。在60gpa和2800k条件下恢复的织构显示铁液渗透到硅酸盐钙钛矿的晶界中。(3)采用同步辐射原位x射线衍射法研究了（Mg,Fe）O的高压高温行为。在所有成分中均观察到菱形畸变。100 GPa左右的高温相为岩盐结构，除FeO端元外，未观察到nias结构相。因此，最下地幔条件下的稳定相应具有岩盐结构。(4)采用原位x射线衍射法对Si0_2的后辉石相进行了检测。在55 GPa以上可以观察到cacl2结构相，在80 GPa和2000 K下可以保持稳定。结果表明，该转变的Clausius-Clapeyron斜率略为正。(5)采用原位x射线衍射法检测铁-水反应。bcc铁与水直接反应生成水合铁，并在较高温度下依次转变为氢化铁和浮氏体。fcc铁经激光加热后反应生成氢化铁和浮士体。这些氢化铁对环境条件是不淬灭的。

In this research, we investigated the properties on some major mantle minerals under high pressure and high temperature using an improved double-sided laser heated diamond anvil cell (LHDAC). The results of this research are followings;(1)We newly developed a laser heating system at Tohoku University, which enable to heat the larger sample stably under pressure. The technical essences were feed backed to construction of in-situ X-ray diffraction system using LHDAC in both Photon Factory and SPring-8.(2) The reaction between iron and silicate perovskite was examined for the pressure range of 30 - 60 GPa. A possibility of reaction which produce iron silicide was detected in the recovered sample after laser heating at 30 GPa. The texture recovered from 60 GPa and 2800 K show a percolation of molten iron into the grain boundary of silicate perovskite.(3) High pressure and high temperature behavior of (Mg,Fe)O was examined using in-situ X-ray diffraction method with synchrotron radiation. A rhombohedral distortion was observed in all compositions. High temperature phase at around 100 GPa has rock salt structure and no NiAs-structured phase was observed except for the end member of FeO. Therefore, the stable phase under the lowermost mantle condition should have rock salt structure.(4) Post stishovite phase of Si0_2 was examined using in-situ X-ray diffraction method. CaCl2-structured phase was observed above 55 GPa, which was stable up to 80 GPa and 2000 K. The results show that the Clausius-Clapeyron slope of this transition is slightly positive.(5) Iron-water reaction was examined using in-situ X-ray diffraction method. The bcc iron directly reacted with water to produce iron hydrate and showed successive transition to iron hydride and wustite at higher temperature. The fcc iron reacted to produce iron hydride and wustite after laser heating. These iron hydride were unquenchable to ambient condition.