Compressibility of Ca3Al2Si3O12 perovskite up to 55 GPa

Abstract : Compressibility of perovskite-structured Ca3Al2Si3O12 grossular (GrPv) was investigated at high pressure and high temperature by means of angle-dispersive powder X-ray diffraction using a laser-heated diamond anvil cell. We observed the Pbnm orthorhombic distortion for the pure phase above 50 GPa, whereas below this pressure, Al-bearing CaSiO3 perovskite coexists with an excess of corundum. GrPv has a bulk modulus (K 0 = 229 ± 5 GPa; K′0 fixed to 4) almost similar to that reported for pure CaSiO3 perovskite. Its unit-cell volume extrapolated to ambient conditions (V 0 = 187.1 ± 0.4 Å3) is found to be ~2.5 % larger than for the Al-free phase. We observe an increasing unit-cell anisotropy with increasing pressure, which could have implications for the shear properties of Ca-bearing perovskite in cold slabs subducted into the Earth’s mantle.
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Steeve Gréaux, Denis Andrault, Laurent Gautron, Nathalie Bolfan-Casanova, Mohamed Mezouar. Compressibility of Ca3Al2Si3O12 perovskite up to 55 GPa. Physics and Chemistry of Minerals, Springer Verlag, 2014, 41, pp.419-429. ⟨10.1007/s00269-014-0673-1⟩. ⟨hal-01133502⟩



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