Phase relations in Mg3Al2Si3 O12 to 180 GPa: Effect of Al on post-perovskite phase transition

Shigehiko Tateno, Kei Hirose, Nagayoshi Sata, Yasuo Ohishi

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    Phase relations in Mg3Al2Si3 O12 (MgSiO3 + 25 mol% Al2O3; pyrope garnet composition) were investigated on the basis of in-situ synchrotron X-ray diffraction measurements at high-pressure and -temperature in a laser-heated diamond anvil cell (LHDAC). Results demonstrate that perovskite is solely stable up to 140 GPa and 2200 K, and perovskite and CaIrO3-type post-perovskite phase (space group: Cmcm) coexist above 140 GPa and 2200 K. Post-perovskite is formed as a single phase above 150-170 GPa. Previous study has shown that pure MgSiO3 perovskite transforms to post-perovskite phase above 125 GPa and 2500 K based on the same pressure standard. These results indicate that addition of Al2O3 expands the stability of MgSiO3 perovskite relative to post-perovskite.

    Original languageEnglish
    Article numberL15306
    JournalGeophysical Research Letters
    Issue number15
    Publication statusPublished - Aug 16 2005

    ASJC Scopus subject areas

    • Geophysics
    • Earth and Planetary Sciences(all)


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