Garnet-biotite thermometer and estimation of crystallization temperature of zoned garnets from metapelites: II. Effect of X_{H_2 O} on estimation accuracy

The fluid regime of medium-grade metapelitic systems was studied with mineral fugometers. It has been established that at least some of the rocks under consideration contain mineral assemblages equilibrated with the participation of fluids with an appreciably lowered mole fraction of the aqueous component (0.4–0.7). The data obtained are used to explain the systematic discrepancy between the temperature estimated with the garnet-biotite geothermometer and the program THERMOCALC. It has been suggested that the negative correlation between the temperature intervals of crystallization and the nucleation temperature of the studied garnets is related to the kinetic features of porphyroblast growth.