Solubility of hydrogen and ferric iron in rutile and TiO2 (II): Implications for phase assemblages during ultrahigh-pressure metamorphism and for the stability of silica polymorphs in the lower mantle

G Bromiley*, N Hilaret, C McCammon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The solubility of hydrogen in Fe2O3-doped rutile and TiO2 (II) at 1100 degreesC has been experimentally determined. H incorporation in rutile is coupled to substitution of Fe3+ onto the octahedral Ti4+ site. In contrast, TiO2 (II) contains no structurally-incorporated hydrogen. The dominant Fe3+ incorporation mechanism in both phases is unrelated to H content, and involves substitution of Fe3+ onto octahedral Ti4+ sites, charge-balanced by oxygen vacancies. Substitution of Fe2O3 into TiO2 (II) stabilizes the structure to much lower pressures than in the pure TiO2 system. Results indicate that Al-bearing stishovite could act as an important carrier of water in subducting oceanic crust, but that formation of the post-stishovite phase with the alpha-PbO2 structure would represent a significant dehydration event at the base of the lower mantle.

Original languageEnglish
Article number04610
Number of pages5
JournalGeophysical Research Letters
Volume31
Issue number4
DOIs
Publication statusPublished - 24 Feb 2004

Keywords

  • WATER
  • STISHOVITE
  • MINERALS
  • ABSORPTION
  • SUBSTITUTION
  • MORB

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