Ultrahydrous stishovite from high-pressure hydrothermal treatment of SiO 2

Kristina Spektor, Johanna Nylen, Emil Stoyanov, Alexandra Navrotsky, Richard Hervig, Kurt Leinenweber, Gregory P. Holland, Ulrich Häussermann

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23 Scopus citations

Abstract

Stishovite (SiO 2 with the rutile structure and octahedrally coordinated silicon) is an important high-pressure mineral. It has previously been considered to be essentially anhydrous. In this study, hydrothermal treatment of silica glass and coesite at 350-550°C near 10 GPa produces stishovite with significant amounts of H 2O in its structure. A combination of methodologies (X-ray diffraction, thermal analysis, oxide melt solution calorimetry, secondary ion mass spectrometry, infrared and nuclear magnetic resonance spectroscopy) indicate the presence of 1.3 ± 0.2 wt% H 2O and NMR suggests that the primary mechanism for the H 2O uptake is a direct hydrogarnet-like substitution of 4H + for Si 4+, with the protons clustered as hydroxyls around a silicon vacancy. This substitution is accompanied by a substantial volume decrease for the system (SiO 2 + H 2O), although the stishovite expands slightly, and it is only slightly unfavorable in energy. Stishovite could thus be a host for H 2O at convergent plate boundaries, and in other relatively cool high-pressure environments.

Original languageEnglish (US)
Pages (from-to)20918-20922
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume108
Issue number52
DOIs
StatePublished - Dec 27 2011

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Keywords

  • High-pressure synthesis
  • Hydrothermal environments
  • Low temperature
  • Multianvil technique

ASJC Scopus subject areas

  • General

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