Post-spinel transition in Mg2SiO4 determined by high P - T in situ X-ray diffractometry

Tomoo Katsura, Hitoshi Yamada, Toru Shinmei, Atsushi Kubo, Shigeaki Ono, Masami Kanzaki, Akira Yoneda, Michael J. Walter, Eiji Ito, Satoru Urakawa, Kenichi Funakoshi, Wataru Utsumi

Research output: Contribution to journalArticle

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Abstract

The phase boundary of the post-spinel transition in Mg2SiO4 was re-investigated by means of high P - T in situ X-ray diffractometry with a gold pressure marker in a Kawai-type apparatus. Rapid and continuous temperature changes were conducted to initiate dissociation of spinel, which tends to be inert after long annealing. Isothermal decompression at high temperature was conducted to form spinel from perovskite plus periclase. The phase boundary is located at ca. 22 GPa in the temperature range from 1550 to 2100 K, which is 1-1.5 GPa lower than the 660 km discontinuity. This discrepancy might be explained in terms of the pressure effect of thermocouple emf and inaccurate equation of state (EOS) for the pressure maker. The transition is found to be less sensitive to temperature than reported previously, with a Clapeyron slope ranging from -2 to -0.4 MPa/K. This small Clapeyron slope implies that the post-spinel transition would not be an effective barrier to mantle convection.

Original languageEnglish
Pages (from-to)11-24
Number of pages14
JournalPhysics of the Earth and Planetary Interiors
Volume136
Issue number1-2
DOIs
Publication statusPublished - Apr 15 2003

Fingerprint

spinel
x rays
periclase
slopes
pressure effect
mantle convection
temperature
pressure reduction
perovskite
annealing
pressure effects
thermocouples
decompression
equation of state
markers
discontinuity
Earth mantle
convection
equations of state
gold

Keywords

  • 660 km discontinuity
  • High pressures and temperatures
  • In situ X-ray diffractometry
  • Mantle
  • MgSiO
  • Post-spinel transition

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this

Post-spinel transition in Mg2SiO4 determined by high P - T in situ X-ray diffractometry. / Katsura, Tomoo; Yamada, Hitoshi; Shinmei, Toru; Kubo, Atsushi; Ono, Shigeaki; Kanzaki, Masami; Yoneda, Akira; Walter, Michael J.; Ito, Eiji; Urakawa, Satoru; Funakoshi, Kenichi; Utsumi, Wataru.

In: Physics of the Earth and Planetary Interiors, Vol. 136, No. 1-2, 15.04.2003, p. 11-24.

Research output: Contribution to journalArticle

Katsura, Tomoo ; Yamada, Hitoshi ; Shinmei, Toru ; Kubo, Atsushi ; Ono, Shigeaki ; Kanzaki, Masami ; Yoneda, Akira ; Walter, Michael J. ; Ito, Eiji ; Urakawa, Satoru ; Funakoshi, Kenichi ; Utsumi, Wataru. / Post-spinel transition in Mg2SiO4 determined by high P - T in situ X-ray diffractometry. In: Physics of the Earth and Planetary Interiors. 2003 ; Vol. 136, No. 1-2. pp. 11-24.
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