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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L13313, doi:10.1029/2005GL023219, 2005

Clapeyron slope of the post-perovskite phase transition in CaIrO3

Kei Hirose

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan


Yosuke Fujita

Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan


Abstract

The Clapeyron slope of the perovskite to post-perovskite phase transition has not been well determined experimentally. Crystal structure of CaIrO3 is equivalent to the MgSiO3 post-perovskite phase (space group: Cmcm) at ambient condition. We have found that perovskite phase (Pbnm) of CaIrO3, which is isostructural with MgSiO3 perovskite, is stable at 1–3 GPa and 1400–1550°C. The perovskite to post-perovskite phase transition in CaIrO3 was determined by using piston-cylinder apparatus at 0.9–3.0 GPa and 1350–1550°C. Results show that phase transition pressure is strongly temperature-sensitive with a Clapeyron slope of +17(±3) MPa/°C. These results, obtained for a suitable analogue material, suggest that post-perovskite phase transition in MgSiO3 also has a large positive value of the Clapeyron slope. Such a pronounced exothermic reaction in the Earth's lowermost mantle will promote the upwelling of high-temperature plumes from the core-mantle boundary region.

Received 13 April 2005; accepted 8 June 2005; published 14 July 2005.

Index Terms: 3630 Mineralogy and Petrology: Experimental mineralogy and petrology; 3924 Mineral Physics: High-pressure behavior; 3939 Mineral Physics: Physical thermodynamics; 8121 Tectonophysics: Dynamics: convection currents, and mantle plumes; 8124 Tectonophysics: Earth's interior: composition and state (1212, 7207, 7208, 8105).

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 147354 bytes)

Citation: Hirose, K., and Y. Fujita (2005), Clapeyron slope of the post-perovskite phase transition in CaIrO3, Geophys. Res. Lett., 32, L13313, doi:10.1029/2005GL023219.