Calibration of a Ti-in-muscovite geothermometer for ilmenite- and Al2SiO5-bearing metapelites

• An empirical Ti-in-muscovite geothermometer is calibrated.
• The calibration conditions are 450–800 °C at 0.1–1.4 GPa for metapelitic muscovites with Ti atom > 0.01.
• This thermometer applies to ilmenite- and Al2SiO5-bearing metapelites.

The Ti-in-muscovite geothermometer was empirically calibrated as ln[T(oC)] = 7.258 + 0.289 ln(Ti) + 0.158[Mg/(Fe + Mg)] + 0.031 ln[P(kbar)] using ilmenite- and Al2SiO5-bearing assemblages in metapelites under P–T conditions of 450–800 °C and 0.1–1.4 GPa. The calibration was conducted for muscovites containing Ti = 0.01–0.07, Fe = 0.03–0.16, Mg = 0.01–0.32 and Mg/(Fe + Mg) = 0.05–0.73, respectively, on the basis of 11 oxygen per formula unit. Such compositional range covers more than 90% natural muscovites, and the random error of this thermometer is estimated to be of ± 65 °C. The geothermometer was validated against a set of independently determined temperature conditions between different degrees in samples from different prograde, inverted and contact metamorphic terranes. Application of this thermometer beyond the calibration conditions is not encouraged.