Metamorphic evolution of high-alumina metapelites near the Panimba overthrust (Yenisei Range): Mineral associations, PT-conditions, and tectonic model

An attempt is made to study pressure-heterogeneous high-alumina metapelites of andalusite-silimanite and kyanite-sillimanite facies series for clearin g up the PT-evolution of metamorphism related to thrusting tectonics. As a result of detailed research wit the use of geothermobarometry and THERMOCAL C-based analysis of mineral equilibria, PT-conditions were estimated and PT -paths of evolution were plotted for moderate and elevated pressures. The o btained data on the change of PT-conditions of metamorphism suggest that th e kyanite substitution for andalusite and other mineral transformations wer e caused by an increase in pressure under low geothermal gradient, describe d by a model for tectonic thickening of the crust sin the zone of the Panim ba overthrust. The absence of a marked increase in temperature on thrusting is explained by specific behavior of stationary geotherms for different ki nds of rocks that have different thermophysical and heat-producing properti es.