Assessment of the Garnet-Clinopyroxene Thermometer

A thermometer based on the MgFe−1 exchange equilibrium between garnet and clinopyroxene is formulated by using new experimental data measured at 600° to 950°C, 0.8 to 3.0 GPa, and f(O2) defined by the fayalite-quartz-magnetite buffer in the basalt-H2O system. The new formulation is T = 3820 / 1.828 + lnKD (1 + a(2.2 − p)), where T is temperature (K), P is pressure (GPa), KD is the Fe-Mg partition coefficient between garnet and clino-pyroxene, defined as KD = (Fe2+/Mg)garnet/(Fe2+/Mg) clinopyroxene, and a = 132/T. Application of the thermometer to rocks in amphibolite, granulite, and eclogite terranes yields temperatures that are in reasonable agreement with other well-calibrated thermometers and the experimental calibrations by Ellis and Green (1979) and Pattison and Newton (1989).