Volatile-Bearing Phases at High Pressures and Temperatures: Volatile Release and Retention in Earth's Mantle

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The amount of water retained at depth within the Earth, and particularly within Earth's mantle, is a topic of key importance for understanding (1) the genesis and long-term volume of Earth?s oceans; (2) the genesis of magmas within the deep interior of the Earth, and thus the occurrence of volcanism in subduction-related environments, such as the circum-Pacific ring-of-fire; and (3) the viscous behavior of the deep planet, and hence for how the mantle flows and plate tectonics occurs. By the same token, the retention of carbon dioxide within the deep Earth is of critical importance for not only how much carbon the planet retains, but also for how much carbon dioxide has been cycled between the surface and the interior (and vice-versa). This project is designed to probe the properties at the high pressures and temperatures of Earth?s interior of a range of minerals known to retain water or carbon dioxide at either subduction zone or deeper mantle conditions. It is oriented towards providing data that will constrain how much water and carbon dioxide is retained at depth through, for example, constraining the likely presence and abundance of water and carbon-containing minerals at depth (through their likely signature in seismic studies) and their geochemical behavior (through probing their stability and high-pressure phase transitions).Specifically, the volatile-bearing phases lawsonite, topaz, phlogopite, dolomite and phase D will be primarily targeted, as these represent major volatile-bearing phases within material that is subducted from the near-surface into the planet's interior. Both x-ray diffraction and spectroscopic probes will be utilized, and the focus will be on simultaneous high-pressure and high-temperature experiments-these will take advantage of both extant and recently augmented high-pressure, high-temperature capabilities. These studies build and expand on a broad suite of characterizations of hydrogen- and carbon-bearing phases on compression at 300 K conducted by the PI and collaborators. The results will provide new constraints on the bonding properties of water and carbon within minerals at high pressures and temperatures, as well as on the thermodynamic properties (and particularly the equations of state) of these materials.