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Experimental study on the melting relation of silicate under the lowermost mantle condition

下地幔条件下硅酸盐熔融关系的实验研究

基本信息

批准号：
16340164
负责人：
KONDO Tadashi
金额：
$ 10.56万
依托单位：
Osaka University (2006)Tohoku University (2004-2005)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

In this research project, we investigated the phase relation of the minerals under the lowermost mantle condition and the chemical reaction between those minerals and molten iron up to the condition corresponding to the earth's core-mantle boundary. For realizing such extreme conditions, we newly designed a symmetrical diamond anvil cell with a wide conical window for laser-heating and optical spectroscopy. The laser-heating system was also refined for stable heating and optimal temperature measurement from the hot sample by a spectroradiometric method. Experiments were performed using these techniques at SPring-8 and Photon Factory for in-situ X-ray diffraction measurements at high P-T, and also at laboratory for recovery runs to check the quenched samples. Thanks for the recent advances in micro-processing technologies such as laser cutting, focused ion beam, we successfully prepared the thin section of the recovered samples for analytical transmission electron microscopy. Finally we … More obtained the following results. (1) The chemical reaction between molten iron and perovskite and post-perovskite phase and wetting property at the core-mantle boundary condition was examined, and silicon and oxygen turned to be important candidates as light elements in the outer core. The wetting angle between post-perovskite phase and molten iron was slightly higher than the critical angle of 60°, which means 2wt% of the core material can be trapped in the D" layer. (2) Magnesiowustite is the heaviest minerals overall the mantle based on the iron partitioning experiments between magnesium oxide and silicate perovskite and post-perovskite phase. No evidence for the effect of a high-spin to low-spin transition was found in these minerals. (3) Potassium can be dissolved into molten iron significantly at core-mantle boundary condition, and the element may work as a heat source in the core. (4) The hydrous mineral, delta-AIOOH, has a wide stability field over 100GPa and 2000K, therefore this phase at relatively low temperature condition in descending slab possibly survive to the lowermost mantle to supply the water to core-mantle boundary. (5) Potassium bearing silicate with post-hollandite structure can be stably exist at the lowermost mantle condition. Less

本研究项目主要研究了地幔最低层条件下矿物的相关系以及直到地球核幔边界条件下矿物与铁水之间的化学反应。为了实现这样的极端条件，我们新设计了一个对称的金刚石对顶砧激光加热和光谱宽锥窗口。激光加热系统也进行了改进，稳定的加热和最佳的温度测量从热样品的光谱辐射法。在SPring-8和Photon Factory使用这些技术进行了实验，用于在高P-T下进行原位X射线衍射测量，并且还在实验室进行了恢复运行以检查淬火样品。由于激光切割、聚焦离子束等微加工技术的最新进展，我们成功地制备了用于分析透射电子显微镜的回收样品的薄切片。最后我们 ...更多信息获得了以下结果。(1)研究了铁液与钙钛矿和后钙钛矿相的化学反应以及核幔边界条件下的润湿性，发现硅和氧是外核轻元素的重要候选者。后钙钛矿相和熔融铁之间的润湿角略高于60°的临界角，这意味着2wt%的芯材料可以被捕获在D”层中。(2)镁橄榄石是地幔中最重的矿物，镁氧化物和硅酸盐钙钛矿和后钙钛矿相之间的铁分配实验。在这些矿物中没有发现高自旋到低自旋转变的证据。(3)在核幔边界条件下，钾元素能显著地溶解于铁液中，并在核内起到热源的作用。(4)含水矿物δ-AlOOH在100 GPa和2000 K以上具有较宽的稳定域，因此，该相在下降板片中的相对低温条件下可能存活到地幔最下部，为核幔边界提供水分。(5)具有后硬硅钙石结构的含钾硅酸盐在地幔最下部条件下可以稳定存在。少