Determination of the phase boundary between ilmenite and perovskite in MgSiO3 by in situ X-ray diffraction and quench experiments |
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Authors: | K Kuroda T Irifune T Inoue N Nishiyama M Miyashita K Funakoshi W Utsumi |
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Institution: | (1) Department of Earth Sciences, Ehime University, 2-5 Bunkyo-cho, Matsuyama 790-8577, Japan e-mail: irifune@dpc.ehime-u.ac.jp Tel.: +81-89-9279645 Fax: +81-89-9279640, JP;(2) Japan Synchrotron Radiation Research Institute, 323-3 Mihara, Mikazuki-cho, Sayo-gun, Hyogo 679-5198, Japan, JP |
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Abstract: | Determination of the phase boundary between ilmenite and perovskite structures in MgSiO3 has been made at pressures between 18 and 24 GPa and temperatures up to 2000 °C by in situ X-ray diffraction measurements
using synchrotron radiation and quench experiments. It was difficult to precisely define the phase boundary by the present
in situ X-ray observations, because the grain growth of ilmenite hindered the estimation of relative abundances of these phases.
Moreover, the slow reaction kinetics between these two phases made it difficult to determine the phase boundary by changing
pressure and temperature conditions during in situ X-ray diffraction measurements. Nevertheless, the phase boundary was well
constrained by quench method with a pressure calibration based on the spinel-postspinel boundary of Mg2SiO4 determined by in situ X-ray experiments. This yielded the ilmenite-perovskite phase boundary of P (GPa) = 25.0 (±0.2) – 0.003
T (°C) for a temperature range of 1200–1800 °C, which is generally consistent with the results of the present in situ X-ray
diffraction measurements within the uncertainty of ∼±0.5 GPa. The phase boundary thus determined between ilmenite and perovskite
phases in MgSiO3 is slightly (∼0.5 GPa) lower than that of the spinel-postspinel transformation in Mg2SiO4.
Received: 19 May 1999 / Accepted: 21 March 2000 |
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Keywords: | Ilmenite Perovskite In situ X-ray diffraction Phase boundary High pressure |
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