On the mechanisms for H and Al incorporation in stishovite

Geoffrey D. Bromiley*, Fiona A. Bromiley, David W. Bromiley

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The solubility and incorporation mechanisms of hydrogen in synthetic stishovite as a function of Al(2)O(3) content have been investigated. Mechanisms for H incorporation in stishovite are more complex than previously thought. Most H in stishovite is incorporated via the Smyth et al. ( Am Mineral 80: 454 456, 1995) model, where H docks close to one of the shared O - O edges, giving rise to an OH stretching band in infrared (IR) spectra at 3,111 - 3,117 cm(-1). However, careful examination of IR spectra from Alstishovite reveals the presence of an additional OH band at 3,157 - 3,170 cm(-1). All H is present on one site, with interstitial H both coupled to Al(3+) substitutional defects on adjacent octahedral (Si(4+)) sites, and decoupled from other defects, giving rise to two distinct absorption bands. Trends in IR data as a function of composition are consistent with a change in Al incorporation mechanism in stishovite, with Al(3+) substitution for Si(4+) charge-balanced by oxygen vacancies at low bulk Al(2)O(3) contents, and coupled substitution of Al(3+) onto octahedral (Si(4+)) and interstitial sites at high bulk Al(2)O(3) contents. Trends in OH stretching frequencies as a function of Al(2)O(3) content suggest that any such change in Al incorporation mechanism could alter the effect that Al incorporation has on the compressibility of stishovite, as noted by Ono et al. ( Am Mineral 87: 1486 - 1489, 2002).

Original languageEnglish
Pages (from-to)613-621
Number of pages9
JournalPhysics and Chemistry of Minerals
Volume33
Issue number8-9
DOIs
Publication statusPublished - Nov 2006

Keywords / Materials (for Non-textual outputs)

  • RUTILE-TYPE COMPOUNDS
  • TEMPERATURE-DEPENDENCE
  • BEARING STISHOVITE
  • WATER SOLUBILITY
  • LOWER MANTLE
  • HYDROGEN
  • CLINOPYROXENES
  • SUBSTITUTION
  • ABSORPTION
  • PRESSURE

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