摘要：AbstractThe pyrite-type FeO2and FeO2H were synthesized at the pressure-temperature conditions relevant to Earth’s deep lower mantle. Through the water-iron reaction, the pyrite-phase is a good candidate to explain the chemical heterogeneities and seismological anomalies at the bottom of the mantle. The solid solution of pyrite-type FeO2and FeO2H, namely the FeO2Hx(0 ≤ x ≤ 1), is particularly interesting and introduces puzzling chemical states for both the O and H atoms in the deep mantle. While the role of H in the FeO2–FeO2H system has been primarily investigated, discrepancies remain. In this work, we summarize recent progress on the pyrite-phase, including FeO2, FeO2H, and FeO2Hx, which is critical for understanding the water cycling, redox equilibria, and compositional heterogenicities in the deep lower mantle.Graphical abstractDisplay OmittedHighlights•Previous findings on the pyrite-type FeO2–FeO2H system are summarized and reviewed.•The mobility of H in the FeO2–FeO2H system was characterized by x-ray diffraction in diamond anvil cell.•The co-existence of pyrite-type phase with high-low concentrations of H was observed in a quickly decompressed sample.
