Material investigation on Core-Mantle Boundary

在这项研究中，我们利用改进的双面激光加热金刚石压腔(LHDAC)研究了几种主要地幔矿物在高压和高温下的性质。研究结果如下：(1)东北大学新研制了一套激光加热系统，能够在加压下稳定加热较大的样品。(2)在30~60 Gpa的压力范围内，考察了铁与硅酸盐钙钛矿的反应。在30 Gpa激光加热后的回收样品中检测到了生成硅化铁的可能性。在60 GPa和2800K温度下恢复的织构表明，铁水渗入了硅酸盐钙钛矿的晶界。(3)用同步辐射原位X射线衍射法研究了(Mg，Fe)O的高温高压行为。在所有成分中都观察到了菱面体的扭曲。100 Gpa左右的高温相具有岩盐结构，除FeO端元外，没有观察到NiAs结构的相。因此，在最低地幔条件下的稳定相应具有岩盐结构。(4)用原位X射线衍射法对SiO_2的后方辉钛矿相进行了研究。在55 Gpa以上观察到CaCl2结构相，在80 Gpa和2000K下稳定存在。结果表明，这一转变的Clausius-Clapeyron斜率略为正。(5)用原位X射线衍射法研究了铁-水反应。体心立方铁直接与水反应生成水合物，在较高温度下连续转变为氢化铁和纤锌矿。面心立方铁经激光加热后反应生成氢化铁和黄铁矿。这些氢化铁在环境条件下是不可熄灭的。

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.