TESTING TITANIUM-IN-QUARTZ THERMOBAROMETRY AT LOW TEMPERATURES IN VEINS AND DEFORMED QUARTZITE

The accuracy, reliability and best practices of Ti-in-quartz thermobarometry (“TitaniQ;” Wark & Watson, 2006; Thomas et al., 2010) in greenschist facies rocks have not been established. To address these issues we measured Ti concentrations in rutile-bearing samples of quartzite and quartz veins from Taiwan’s Hsuëhshan Range. Temperatures of vein emplacement and recrystallization of quartzite are independently constrained between 250-360° based on a combination of microstructural criteria and Raman Spectroscopy of Carbonaceous Material (Beyssac et al., 2007). Pressures are estimated using a geothermal gradient for the Hsuëhshan Range based on thermokinematic modeling (Simoes et al., 2007).

Ti-in-quartz temperatures for vein emplacement fall within error of the above range of independently constrained temperatures. In quartzites, remnant detrital grains show a wide range of inherited Ti concentration from 0.1 to 200 ppm. Recrystallized quartz (~5% of the samples, with 10-20 µm grain size) has a restricted range of Ti concentrations that peaks at 0.8-2 ppm. Corresponding Ti-in-quartz deformation temperatures of 340° and 349° in two quartzite samples are consistent with independent constraints. These results are promising for the use of Ti-in-quartz thermobarometry to constrain PT conditions of vein-emplacement and quartzite recrystallization in rutile-bearing samples.