Application of the titanium-in-quartz thermometer to pelitic migmatites from the Adirondack Highlands, New York

The 'TitaniQ' (Ti-in-quartz) solubility thermometer was applied to migmatitic metapelites from the southern and western Adirondack Highlands, New York, to examine the effect of granulite facies metamorphism on the distribution of Ti in quartz. Both cathodoluminescence imaging and quantitative traverses revealed that individual grains of Adirondack quartz are highly zoned with respect to Ti, and that core-to-rim decreases of Ti are common. Large ranges in calculated temperature were observed within each sample. One sample, not considered to be saturated with respect to TiO₂, gave maximum temperatures more than 100 °C lower than previously estimated peak temperatures. Rutile-saturated southern and western Adirondack samples yielded peak estimates of ≥803 ± 11 °C and ～860–870 °C, respectively, which are similar to previous estimates from major phase thermometry. Minimum Ti-in-quartz matrix temperatures from rutile-saturated samples are 630 °C, which is interpreted as the closure temperature for Ti diffusion in quartz in these samples. This study demonstrates that Ti-in-quartz thermometry can yield details of rock evolution if the textural setting and reaction history of the quartz is clear, and can yield near-peak metamorphic temperatures in some cases, if care is taken to test for post-peak diffusional resetting.