@article{f8c97ddad3ec4f6e928c14ed759229d6,
title = "Chemical Reactions Between Fe and H2O up to Megabar Pressures and Implications for Water Storage in the Earth's Mantle and Core",
abstract = "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.",
keywords = "Iron, high pressures, high temperatures, pyrite-structured FeOOH, water",
author = "Liang Yuan and Eiji Ohtani and Daijo Ikuta and Seiji Kamada and Jun Tsuchiya and Hirao Naohisa and Yasuo Ohishi and Akio Suzuki",
note = "Funding Information: We thank T. Sakamaki, F. Maeda, and I. Ohira for their experimental assis tance. We thank H. K. Mao for the information on his recent works. Comments from H. K. Mao and an anonymous reviewer have improved this manuscript. This study was sup ported by the JSPS KAKENHI (grants JP15H05748 to E. O., JP15H05828 to A. S., and JP15H05834 to J. T.). J. T. was also supported in part by MEXT as “Exploratory Challenge on Post-K computer” (Frontiers of Basic Science: Challenging the Limits). E. O. was also partly supported by the Ministry of Education and Science of the Russian Federation (Project 14B25.31.0032). S. K. was partly supported by KAKENHI grants 26247089, 15H05831, and 16K13902. The synchrotron radiation experiments were performed at SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (Proposals 2016B1494, 2016B1214, 2017A1474, 2017A1251, 2017A1673, 2017B1514, and 2017B169). L. Y. is supported by the International Joint Graduate Program in Earth and Environmental Science (GP-EES), Tohoku University. Experimental data has been shown in Figures 1–3, S1–S3, and Tables 1, S1 and S2. Publisher Copyright: {\textcopyright}2018. American Geophysical Union. All Rights Reserved.",
year = "2018",
month = feb,
day = "16",
doi = "10.1002/2017GL075720",
language = "English",
volume = "45",
pages = "1330--1338",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "3",
}