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 language | English (US) |
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Pages (from-to) | 369-374 |
Number of pages | 6 |
Journal | Contributions to Mineralogy and Petrology |
Volume | 164 |
Issue number | 2 |
DOIs | |
State | Published - Aug 2012 |
Externally published | Yes |
Keywords
- Quartz
- Thermobarometry
- Thermometry
- Ti-in-quartz
- Trace elements
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology