High-pressure phase equilibria and thermodynamic properties of silicate minerals and related materials in the lower mantle conditions

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Thermodynamic properties of silicate perovskite were measured and used to refine the post-spinel phase transition boundary at high pressure. Stability relations of calcium ferrite and CAS phase which contain large amounts of calcium, aluminum and alkali-metal elements were determined at high pressure. The phases occur as high pressure phases of basaltic crust subducted into the lower mantle. Some metal oxides with the perovskite structure were found to show the post-perovskite transition at lower pressure than that of silicate perovskite which occurs at the lowermost mantle. The high-pressure phase relations and thermodynamic properties of the metal oxides were determined.