Garnet—Biotite Geothermometer and Estimation of Crystallization Temperature of Zoned Garnets from Metapelites: I. Reconstruction of Thermal History of Porphyroblast Growth

摘要

The possibility of using a garnet—biotite geothermometer to estimate the nucleation temperature of zoned crystals is considered. The data on the temperature evolution of mineral systems in the course of porphyroblast growth estimated with different methods are compared for a number of metamorphic provinces. The temperatures for garnet core and rim growth calculated by the program THERMOCALC are systematically overestimated compared to those derived using the garnet—biotite geothermometer (Kaneko and Miyano, 2004; Gulbin, 2011a, 2011b). The discrepancy reaches 40—70°C for the isopleth method and 60— 90°C for the average PT method.