Dissociation of CAS phase in the uppermost lower mantle |
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| Authors: | Kazufusa Ishibashi Kei Hirose Nagayoshi Sata Yasuo Ohishi |
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| Institution: | (1) Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan;(2) Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan;(3) Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan |
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| Abstract: | The high-pressure stability limit of calcium aluminosilicate (CAS) phase has been examined in its end-member CaAl4Si2O11 composition at 18–39 GPa and 1,670–2,300 K in a laser-heated diamond-anvil cell (LHDAC). The in-situ synchrotron X-ray diffraction
measurements revealed that the CAS phase decomposes into three-phase assemblage of cubic Al-bearing CaSiO3 perovskite, Al2O3 corundum, and SiO2 stishovite above 30 GPa and 2,000 K with a positive pressure–temperature slope. Present results have important implications
for the subsolidus mineral assemblage of subducted sediment and the melting phase relation of basalt in the lower mantle. |
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| Keywords: | CAS phase Phase transition Lower mantle X-ray diffraction |
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