The transition of pyrope to perovskite |
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| Authors: | G Serghiou A Zerr A Chopelas R Boehler |
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| Institution: | (1) Max-Planck-Institute for Chemistry, Postfach 3060, 55020 Mainz, Germany Fax: +49-6131-305330, e-mail: serghiou@mpch-mainz.mpg.de, DE |
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| Abstract: | The stability field of Mg3Al2Si3O12-pyrope was examined for the first time under hydrostatic pressure conditions in a CO2-laser heated diamond cell in the pressure range 21–30 GPa between 2300 and 3200 K. The phases were characterized using Raman
and fluorescence spectroscopy. With increasing pressure pyrope transforms to an ilmenite phase above ∼21.5 GPa, to perovskite
plus ilmenite above ∼24 GPa, and to perovskite above 29 GPa. The pressures of the first occurrence of perovskite in this study
are about 2 GPa above the corresponding phase boundary between end-member MgSiO3-ilmenite and perovskite. A small amount of Al2O3 coexists with perovskite up to 43 GPa, as evident from fluorescence spectra resembling those of ruby, but above 43 GPa the
entire Al2O3 content of the pyrope starting material is accommodated in the perovskite structure.
Received: 6 March 1997 / Revised, accepted: 23 July 1997 |
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