Post-stishovite phase boundary in SiO2 determined by in situ X-ray observations

Shigeaki Ono, Kei Hirose, Motohiko Murakami, Maiko Isshiki

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74 Citations (Scopus)

Abstract

A laser heating diamond anvil cell experiment, with an angle-dispersive X-ray diffraction using synchrotron radiation source at the SPring-8, has been developed to observe the phase transition in silica (SiO2) between the P42/ mnm (rutile-type) and Pnnm (CaCl2-type) up to pressures of 100 GPa and at temperature up to 2200 K. The transition was observed in the vicinity of 55 GPa at room temperature, and showed a positive temperature dependence of the transition pressure. The phase boundary was determined to follow the equation P (GPa) = (51 ± 2) + (0.012 ± 0.005) × T (K). Our result gives a transition pressure of near 80 GPa and a depth of 1900 km at an expected lower mantle temperature of 2000-2500 K. Therefore, this SiO2 transition is not the cause of recent observations of seismic anomalies between 800 and 1600 km depth in the mid-lower mantle.

Original languageEnglish
Pages (from-to)187-192
Number of pages6
JournalEarth and Planetary Science Letters
Volume197
Issue number3-4
DOIs
Publication statusPublished - 2002

Keywords

  • Silica
  • Stishovite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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