Garnet-Hornblende Geothermometer: A Comparative Study

The abundance of garnet — hornblende pair in a wide range of rocks primarily from upper green schist to granulite facies has made it one of the most widely used pairs for estimation of temperature at which once rocks equilibrated. Several models of garnet- hornblende thermometer have been formulated by a number of researchers in last four decades. In this contribution, four thermometers: Graham & Powell (1984); Perchuk et al., (1985); Powell, (1985) and Ravna, (2000) formulated since 1984 have been applied. 79 sample data (32 granulites facies, 37 amphibolite facies, 1 greenschist facies, 6 UHP/eclogite facies, 1 UHT and 2 migmatites) from the global literature were collected and processed through the “Gt-Hbl.EXE” software. Based on the present study, the best among all the four models have been identified where the regression bearing on inverse of temperature verses LnKD of each model as well as relation of distribution coefficient on composition were compared. It is concluded that Perchuk et al., (1985) is the most valid and reliable thermometers for a wide range of rock types such as greenschist to eclogite facies.