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Phase transformations in diopside CaMgSi 2 O 6 at pressures Up to 25 GPa

1989; American Geophysical Union; Volume: 16; Issue: 2 Linguagem: Inglês

10.1029/gl016i002p00187

1944-8007

Tetsuo Irifune, Junichi Susaki, Takehiko Yagi, Hiroshi Sawamoto,

Crystal Structures and Properties

Phase transformations in diopside have been studied at pressures up to 25 GPa and at temperatures of 1100 and 1500 °C by a multiple anvil apparatus. The following phase assemblages are found to be stable at given pressures; diopside (15 and 18 GPa), Mg 2 SiO 4 spinel + stishovite + CaSiO 3 perovskite (19 and 20 GPa), MgSiO 3 ilmenite + CaSiO 3 perovskite (22 GPa), and MgSiO 3 perovskite + CaSiO 3 perovskite (24.5 GPa). Electron microprobe analysis reveals that the solubility of the MgSiO 3 molecule in CaSiO 3 cubic perovskite is limited to between 2–5%. The solubility of the CaSiO 3 molecule in MgSiO 3 orthorhombic perovskite is more restricted, being of the order of 2% or less. These results are contradictory to earlier work in which diopside is reported to transform into a cubic perovskite structure of the same composition above 22–23 GPa.