KINETICS OF KYANITE-]ANDALUSITE, KYANITE-]SILLIMANITE, AND ANDALUSITE-]SILLIMANITE TRANSFORMATIONS (EXPERIMENTAL-DATA)

The monovariant association method has been applied to experimental study of kinetics of kyanite-->andalusite, kyanite-->sillimanite, and andalusite-->sillimanite transformations in the temperature interval 720 to 820-degrees-C and 4-5 kbar pressure. The value of activation energy is the same for any of the transformation considered and could assumed to be 112 +/- 38 kJ/mol if the constant value of reaction affinity is accounted for. For the simplest model assuming that the grains are adjacent one another and the process is not limited by diffusion, expressions are presented for the transformation rates (in mol/cm2S) which can be used for estimations of the time required for the transformations in minerals in the nature.