High-pressure experiments have provided us with basic knowledge of mantle mineralogy. While many mineralogical models of the mantle have been developed by comparing the high-pressure experimental results in relatively simplified systems, such as the system MgO-FeO-SiO2, with the observed seismic data, detailed models require accurately measured physical properties of mantle minerals and phase equilibrium data in systems relevant to mantle compositions including components such as Al2O3, Fe2O3, and CaO. The aim of this proposal is to understand the role of Al2O3, Fe2O3, and CaO in the Earth's lower mantle. Specifically, this research is designed (1) to determine the crystal structures of Al- and Al-Ca-rich phases formed in natural basaltic composition under lower mantle conditions, (2) to understand the role of Al3+ and Fe3+ substitutions in the (Mg,Fe)SiO3-perovskite structure, and (3) to determine the effect of Al3+ and Fe3+ substitutions on equations-of-state of (Mg,Fe)SiO3-perovskite. The results from this proposal will be used to determine the density of subducted basaltic crust at lower mantle pressures and therefore to understand the fate of the subducted basaltic crust in the mantle and associated mantle dynamics. The results will provide further understanding of the crystal chemistry of Al3+ and Fe3+-bearing (Mg,Fe)SiO3-perovskites and the chemistry of the lower mantle
