Evidence for oxygenation of Fe-Mg oxides at mid-mantle conditions and the rise of deep oxygen

作     者：Jin Liu Chenxu Wang Chaojia Lv Xiaowan Su Yijin Liu Ruilian Tang Jiuhua Chen Qingyang Hu Ho-Kwang Mao Wendy L.Mao Jin Liu;Chenxu Wang;Chaojia Lv;Xiaowan Su;Yijin Liu;Ruilian Tang;Jiuhua Chen;Qingyang Hu;Ho-Kwang Mao;Wendy L.Mao

作者机构：Center for High Pressure Science and Technology Advanced Research (HPSTAR) Department of Geological SciencesStanford University School of Earth and Space SciencesPeking University SLAC National Accelerator Laboratory Center for Study of Matter at Extreme ConditionsDepartment of Mechanical and Materials Engineering Florida International University 

出 版 物：《National Science Review》 (国家科学评论(英文版))

年 卷 期：2021年第8卷第4期

页      面：29-34页

核心收录：

学科分类：070904[理学-构造地质学] 0709[理学-地质学] 07[理学] 

基　　金：supported by the National Natural Science Foundation of China (NSFC)(U1930401) support from the National Science Foundation(NSF) Geophysics Program (EAR 1446969) support from the NSF Geophysics Program (EAR-1723185) supported by NSF Grants EAR-1722515 and EAR-1447438Q supported by NSFC (17N1051–0213) supported by the NSF—Earth Sciences (EAR-1634415) Department of Energy—Geosciences (DEFG02–94ER14466) supported by DOE-NNSA’s Office of Experimental Sciences The Advanced Photon Source is a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357 supported by the NSF under award ECCS-1542152 performed under the contracts of the SPring-8, Japan(2019A1284 and 2019B1203) 

主　　题：subducting slab hydrous phase lower mantle deep oxygen oxygen-excess oxides 

摘      要：As the reaction product of subducted water and the iron core, FeO2with more oxygen than hematite(Fe2O3) has been recently recognized as an important component in the D layer just above the Earth’s core-mantle boundary. Here, we report a new oxygen-excess phase(Mg, Fe)2O3+δ(0 δ 1, denoted as‘OE-phase’). It forms at pressures greater than 40 gigapascal when(Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron(Fe3+) as in Fe2O3but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hxwhich usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth’s mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted(Mg,Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry.