TITANIQ TAKEN TO NEW DEPTHS

New experiments to study titanium solubility in quartz were conducted at conditions not previously explored to extend and improve the Ti-in-quartz solubility model (Thomas et al. 2010) for thermobarometric applications. Starting materials for the experiments included silica glass, anatase, rutile, Ti-enriched silica gel, zirconia, and water. Raman spectroscopy confirmed co-crystallization of quartz, rutile, and zircon from SiO₂-, TiO₂- and ZrSiO₄-saturated hydrothermal fluids. Titanium K-edge X-ray absorption near edge structure (XANES) measurements have demonstrated that Ti⁴⁺ substitutes for Si⁴⁺ on fourfold tetrahedral sites in quartz (Thomas et al. 2010) and in coesite (Osborne et al. 2019). Electron microprobe measurements and cathodoluminescence images show that quartz crystals are relatively homogenous. Importantly, titanium concentrations of quartz crystals grown at the same experimental conditions using several TiO₂-rich starting materials and several different growth media are identical. Addition of the new experimental results to the Ti-in-quartz solubility model has a small but significant effect on the predicted titanium concentrations of quartz crystallized at both low and high pressures.

Osborne ZR, Thomas JB, Nachlas WO, et al (2019) An experimentally calibrated thermobarometric solubility model for titanium in coesite (TitaniC). Contrib Mineral Petrol 174:34. doi: 10.1007/s00410-019-1575-5

Thomas JB, Bruce Watson E, Spear FS, et al (2010) TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz. Contributions to Mineralogy and Petrology 160:743–759. doi: 10.1007/s00410-010-0505-3