Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H₂O to form a previously unknown (Mg, Fe)O₂H_x (x≤1) phase. The (Mg, Fe)O₂H_x has the pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg_0.6Fe_0.4)O or beyond 2300 km for (Mg_0.7Fe_0.3)O. The (Mg, Fe)O₂H_x is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg²⁺, Fe³⁺, and H⁺). This important phase has a number of far-reaching implications including the extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM, and an internal source for modulating oxygen in the atmosphere.

中文翻译：

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H2O 存在下下地幔深部的矿物学


了解地球内部的矿物学是揭示地球演化和动力学的先决条件。在这里，我们进行了模拟深层下地幔（DLM，深度 1800-2890 公里）条件的高压-温度实验，并观察到水存在下令人惊讶的矿物学转变。方镁石，(Mg, Fe)O，是地球上最丰富的氧化物矿物，与H ₂ O反应形成以前未知的(Mg, Fe)O ₂ H _x ( x ≤1)相。 (Mg, Fe)O ₂ H _x具有黄铁矿结构，与主要的硅酸盐相、桥锰矿和后钙钛矿共存。根据镁含量和地热温度，(Mg _0.6 Fe _0.4 )O 的转变可能发生在 1800 km 处，(Mg _0.7 Fe _0.3 )O 的转变可能发生在 2300 km 之外。 (Mg，Fe)O ₂ H _x是氧过剩相，其储存超出最大阳离子价数(Mg ²⁺ 、Fe ³⁺和H ⁺ )的电荷平衡的过量氧。这个重要的阶段具有许多深远的影响，包括极端的氧化还原不均匀性、DLM 中的深层氧储层以及调节大气中氧气的内部来源。