Water in the Deep Interior

There is a growing appreciation that there may exist extensive interaction between Earth's interior and the hydrosphere. The discovery of substantial amounts of hydrogen in nominally anhydrous minerals, the possible imbalance between water entering and exiting the mantle, and the discovery of dense hydrous phases, have all contributed to increasing interest in the state of water in Earth's interior. Earth's mantle is a potentially vast storage site for water. Besides, incorporation of water in crystalline and liquid silicates is known to affect rheological and elastic properties in upper mantle minerals. Our goal is to address the state of hydrogen in hydrous and nominally anhydrous silicates such as the major phase of the lower mantle, MgSiO3-perovskite at relevant conditions. What is the limit on the amount of H that can be stored in the mantle? How much accompanies iron [III], aluminum, magnesium, silicon, and oygen vacancies? Hydrogen in these sites is likely to be delocalized, transiting between oxygen neighbors. (Truhlar, Wentzcovitch, and Baroni)

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