Experimental Study of Water at Deep Mantle Conditions

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Jeanloz 0001087 Understanding the properties of H2O deep inside the Earth has major implications for deciphering the geochemical cycling of water and the possible initiation of melting inside the planet, as well as the geophysically observed properties of the mantle. Thermodynamic analysis even suggests that ice may be present at depth, subducted within cold rapidly-sinking slabs. The proposal requests support for a 2-year experimental effort intended to document 1) the crystal-structural identity, 2) thermal equation of state and 3) melting temperature of crystalline H2O (Ice VII, and potentially other polymorphs) at high pressures and temperatures, providing fundamental constraints on the stability and the geophysically relevant properties (elasticity, density) of H2O phases at lower-mantle pressures, ~20-80 GPa.