Renewal: Mineral Physics Studies under the Pressure-Temperature Conditions of Earth's Deep Lower Mantle

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The investigators believe they have discovered a giant oxygen reservoir at the extreme pressure-temperature conditions between the Earth's deep mantle and iron core. The reservoir consists of previously unknown iron superoxides which could suddenly release its excessive oxygen. In the present project, the team will further explore the different types of iron superoxides, the conditions for the explosive oxygen release, and the consequences of oxygen eruptions. The sporadic eruptions provide a new, unified mechanism for answering questions on a list of seemingly unrelated past events that occurred during Earth's 4.6 billion years history and shaped the present living planet. Where did the oxygen in the air come from? What caused the mass extinctions that killed the dinosaurs and ushered in the mammals? What was the driving force that pushed all continents to merge into a single supercontinent, and later pulled the supercontinent apart to form individual continents? From understanding the Earth's Past and Present, we may gain insights into the Earth's Future.The investigator's recent discovery of high P-T iron superoxides, FeO2 and FeO2Hx with the pyrite-type Pa3 structure has suggested potential paradigm changes in mineral physics and geodynamics of the deep lower mantle. The team proposes to further investigate the high P-T mineral physics properties of the superoxides, including the incorporation of other major components such as MgO2, AlO2 and SiO2 into the Pa3 iron superoxide, its interactions with silicate bridgmanite and post-perovskite, its electronic and magnetic spin states, and its valence states of iron and oxygen. The team will search for other stable structural types in addition to Pa3 for firon-based superoxides with the apparent Fe oxidation state 3+, and determine their elastic wave velocities for comparison for comparison with seismic observations in the deep Earth. The team's previous research suggested the existence of a massive amount of oxygen-rich patches at the core-mantle boundary. This research will investigate the metastability of such giant oxygen reservoirs, and the consequences when the stored oxygen is released, particularly the resulting geodynamics of the super plate tectonics that may explain the origin of merging and rifting of supercontinents.