EXPERIMENTAL STUDY OF AMPHIBOLE-GARNET EQUILIBRIUM (CALCIUM-FREE SYSTEM)

Abstract

The equilibrium of amphibole (Am) and garnet (Gr) was one of the first geothermometers to be used in petrological investigations. Its theory was developed already in 1967, but since then it has undergone no appreciable changes. Moreover, its last empirical calibration merely demonstrated its fairly high accuracy. However, the equilibrium of the exchange reaction has not been experimentally checked. Therefore is it impossible to estimate the absolute error of this geothermometer and to describe it thermodynamically, i.e., to determine the energy contributions of the concentrations of Ca, Al, Na and several other components in the minerals in equilibrium on the distribution of Fe and Mg among them. The authors present two approaches they used to solve this problem