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National Science Review 2020年第1期7卷 224-232页

作者： Eiji Ohtani Graduate School of Science Tohoku University

Geophysical observations suggest that the transition zone is wet locally. Continental and oceanic sediment components together with the basaltic and peridotitic components might be transported and accumulated in the transition zone. Low-velocity anomalies at the upper mantle–transition zone boundary might be caused by the existence of dense hydrous magmas. Water can be carried farther into the lower mantle by the slabs. The anomalous Q and shear wave regions locating at the uppermost part of the lower mantle could be caused by the existence of fluid or wet magmas in this region because of the water-solubility contrast between the minerals in the transition zone and those in the lower mantle. δ-H solid solution AlO2H–MgSiO4H2carries water into the lower mantle. Hydrogen-bond symmetrization exists in high-pressure hydrous phases and thus they are stable at the high pressures of the lower mantle. Thus, theδ-H solid solution in subducting slabs carries water farther into the bottom of the lower mantle. Pyrite FeO2Hxis formed due to a reaction between the core and hydrated slabs. This phase could be a candidate for the anomalous regions at the core–mantle boundary.

关键词： water hydrous phase subducting slab transition zone lower mantle hydrogen-bond symmetrization core–mantle boundary

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

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National Science Review 2021年第4期8卷 29-34页

作者： Jin Liu Chenxu Wang Chaojia Lv Xiaowan Su Yijin Liu Ruilian Tang Jiuhua Chen Qingyang Hu Ho-Kwang Mao Wendy L.Mao Center for High Pressure Science and Technology Advanced Research (HPSTAR) Department of Geological Sciences Stanford University School of Earth and Space Sciences Peking University SLAC National Accelerator Laboratory Center for Study of Matter at Extreme Conditions Department of Mechanical and Materials Engineering Florida International University

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 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.

关键词： subducting slab hydrous phase lower mantle deep oxygen oxygen-excess oxides

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