Stability of majorite (Mg, Fe)SiO3 at high pressures and 1800°C

Eiji Ohtani, Naohiro Kagawa, Kiyoshi Fujino

doi:10.1016/0012-821x(91)90005-3

Stability of majorite (Mg, Fe)SiO3 at high pressures and 1800°C

DOI Web Site Web Site 被引用文献9件

書誌事項

公開日: 1991-02

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DOI

10.1016/0012-821x(91)90005-3

公開者: Elsevier BV

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説明

Abstract Phase relations in the system MgSiO 3 -FeSiO 3 were studied experimentally up to a pressure of 24 GPa at 1800°C. Alumina-free tetragonal garnet exists in the pressure range from 16 to 23.5 GPa. The compositional range of the tetragonal garnet phase extends from pure MgSiO 3 to (Mg 0.76 Fe 0.24 )SiO 3 at 18.2 GPa and 1800°C. The sequence of the phase transitions in Mg-rich part of this system at 1800°C is: clinopyroxene→17GPatetragonal garnet→22.5GPailmenite→23GPaMg-perovskite. The lattice constants of tetragonal garnet increase with increasing iron content from a = 11.517 ± 0.002Aandc = 11.435 ± 0.003Afor MgSiO 3 toa = 11.543 ± 0.002A and c = 11.476 ± 0.003A for (Mg 0.76 Fe 0.24 )SiO 3 . Cubic garnet was not observed in the pressure and temperature range studied in this work. The alumina-free tetragonal garnet observed in this study may exist in the harzbergite layer in the descending slab.