Application of the Ti-in-quartz thermobarometer to rutile-free systems. Reply to: A comment on: 'TitaniQ under pressure: The effect of pressure and temperature on the solubility of Ti in quartz' by Thomas et al

Jay B. Thomas, E. Bruce Watson

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

The premise of the Wilson et al. comment is that the Ti-in-quartz solubility calibration (Thomas et al. in Contrib Mineral Petrol 160:743-759, 2010) is fundamentally flawed. They reach this conclusion because P-T estimates using the Ti-in-quartz calibration differ from their previous interpretations for crystallization conditions of the Bishop and Oruanui rhyolites. If correct, this assertion has far-reaching implications, so a careful assessment of the Wilson et al. reasoning is warranted. Application of the Ti-in-quartz calibration as a thermobarometer in rutile-free rocks requires an estimation of TiO 2 activity in the liquid (a TiO2 (liquid-rutile); referenced to rutile saturation) and an independent constraint on either P or T to obtain the crystallization temperature or pressure, respectively. The foundation of Wilson et al.'s argument is that temperature estimates obtained from Fe-Ti oxide thermometry accurately reflect crystallization conditions of quartz in the two rhyolites discussed. We maintain that our experimental approach is sound, the thermodynamic basis of the Ti-in-quartz calibration is fundamentally correct, and our experimental results are robust and reproducible. We suggest that the reason Wilson et al. obtain implausible pressure estimates is because estimates for T and a TiO2 they used as input values for the Ti-in-quartz calibration are demonstrably too high. Numerous studies show that Fe-Ti oxide temperature estimates of some rhyolites are substantially higher than those predicted by well-constrained phase equilibria. In this reply, we show that when reasonable input values for T and a TiO2 (liquid-rutile) are used, pressure estimates obtained from the Ti-in-quartz calibration are well aligned with phase equilibria and essentially identical to melt inclusion volatile saturation pressures.

Original languageEnglish (US)
Pages (from-to)369-374
Number of pages6
JournalContributions to Mineralogy and Petrology
Volume164
Issue number2
DOIs
StatePublished - Aug 1 2012
Externally publishedYes

Keywords

  • Quartz
  • Thermobarometry
  • Thermometry
  • Ti-in-quartz
  • Trace elements

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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