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Phase transition in CaSiO3 perovskite |
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| Authors: | Tetsuya Komabayashi Kei Hirose Nagayoshi Sata Yasuo Ohishi Leonid S. Dubrovinsky |
| Affiliation: | aDepartment of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan bBayerisches Geoinstitut, Universität Bayreuth, Bayreuth 95440, Germany cInstitute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Kanagawa 237-0061, Japan dJapan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan |
| Abstract: | A phase transition in pure CaSiO3 perovskite was investigated at 27 to 72 GPa and 300 to 819 K by in-situ X-ray diffraction experiments in an externally-heated diamond-anvil cell. The results show that CaSiO3 perovskite takes a tetragonal form at 300 K and undergoes phase transition to a cubic structure above 490–580 K in a pressure range studied here. The transition boundary is strongly temperature-dependent with a slightly positive dT / dP slope of 1.1 (± 1.3) K/GPa. It is known that the transition temperature depends on Al2O3 content dissolved in CaSiO3 perovskite [Kurashina et al., Phys. Earth Planet. Inter. 145 (2004) 67–74]. The phase transition in CaSiO3(+ 3 wt.% Al2O3) perovskite therefore could occur in a cold subducted mid-oceanic ridge basalt (MORB) crust at about 1200 K in the upper- to mid-lower mantle. This phase transition is possibly ferroelastic-type and may cause large seismic anomalies in a wide depth range. |
| Keywords: | CaSiO3 perovskite phase transition in-situ X-ray diffraction externally-heated diamond-anvil cell |
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