Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6447460 | Physics of the Earth and Planetary Interiors | 2016 | 10 Pages |
Abstract
Phase relations in the system MgSiO3-Al2O3 have been determined for pressures from 15 to 52Â GPa and at a temperature of 2000Â K from in situ synchrotron X-ray diffraction measurements obtained using sintered diamond anvils in a multi-anvil apparatus. A wide two-phase region of garnet and corundum is found to exist up to 27Â GPa; at higher pressures, a phase assemblage of aluminous bridgmanite and corundum is stabilized. The solubility of Al2O3 in bridgmanite and that of MgSiO3 in corundum are highly dependent on pressure; the Al2O3 content in bridgmanite increases from 12Â mol% at 27Â GPa to 29Â mol% at 52Â GPa, forming bridgmanite with the pyrope composition (25Â mol% Al2O3) at about 45Â GPa. In contrast, the MgSiO3 content in corundum decreases from 24Â mol% at 27Â GPa to 9Â mol% at 52Â GPa. The minimum pressure where the pyropic bridgmanite is formed is significantly higher than the result of the earlier study (â¼37Â GPa) on the pyrope composition. These results suggest the Al2O3 content in bridgmanite and the MgSiO3 content in corundum are good pressure indicators in the mixed-phase region at pressures above 30Â GPa, where virtually no pressure references are available for quench experiments. The new phase diagram in the system MgSiO3-Al2O3 confirms that bridgmanite is the dominant host mineral for Al2O3 in the pyrolitic or peridotitic compositions under the pressure and temperature conditions of the Earth's lower mantle.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geophysics
Authors
Zhaodong Liu, Tetsuo Irifune, Masayuki Nishi, Yoshinori Tange, Takeshi Arimoto, Toru Shinmei,