Chemical Reactions Between Fe and H2O up to Megabar Pressures and Implications for Water Storage in the Earth's Mantle and Core
Chemical Reactions Between Fe and H2O up to Megabar Pressures and Implications for Water Storage in the Earth's Mantle and Core
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DOI：
10.1002/2017gl075720
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发表时间：
2018-02
影响因子：
5.2
通讯作者：
Liang Yuan;E. Ohtani;D. Ikuta;S. Kamada;J. Tsuchiya;Hirao Naohisa;Y. Ohishi;A. Suzuki
中科院分区：
文献类型：
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作者：
Liang Yuan;E. Ohtani;D. Ikuta;S. Kamada;J. Tsuchiya;Hirao Naohisa;Y. Ohishi;A. Suzuki
我们基于原位X射线衍射实验和第一性原理计算研究了高压下Fe-H2O体系的相关系，并证明了FeHx和FeO存在于小于~78 GPa的压力下。最近报道的黄铁矿结构的氧化铁被确定在Fe-H2O系统在激光加热后的压力大于~78 GPa。在这项研究中观察到的相具有比先前报道的Fe-O二元系统中产生的FeO 2大8%-11%的晶胞体积，这表明氢可能保留在FeO 2 Hx晶体结构中。我们的观测结果表明，H2O可能是在金属核的吸积和分离过程中通过铁和水的反应引入到地球深部的。此外，Fe和H2O之间的反应将发生在核幔边界，因为水从与金属核相交的含水俯冲板中释放出来。含挥发性铁化合物的积累可能为下地幔底部观察到的神秘地震结构提供新的见解。
We investigated the phase relations of the Fe‐H2O system at high pressures based on in situ X‐ray diffraction experiments and first‐principles calculations and demonstrate that FeHx and FeO are present at pressures less than ~78 GPa. A recently reported pyrite‐structured FeO2 was identified in the Fe‐H2O system at pressures greater than ~78 GPa after laser heating. The phase observed in this study has a unit cell volume 8%–11% larger than that of FeO2, produced in the Fe‐O binary system reported previously, suggesting that hydrogen might be retained in a FeO2Hx crystal structure. Our observations indicate that H2O is likely introduced into the deep Earth through reaction between iron and water during the accretion and separation of the metallic core. Additionally, reaction between Fe and H2O would occur at the core‐mantle boundary, given water released from hydrous subducting slabs that intersect with the metallic core. Accumulation of volatile‐bearing iron compounds may provide new insights into the enigmatic seismic structures observed at the base of the lower mantle.