EVOLUTION OF METAMORPHISM AND ITS GEOLOGIC SIGNIFICANCE IN ALTAIDES, XINJIANG

There are low-pressure andalusite sequence metamorphic belt and medium-pressure kyanite sequence metamorphic belt occurring in Altaides. The andalusite sequence metamorphic belt includes biotite zone, garnet zone, staurolite zone, staurolite-andalusite zone, sillimanite zone and sillimanite-cordierite zone. The kyanite sequence metamorphic belt includes biotite zone, garnet zone, staurolite zone, kyanite zone, sillimanite zone. It is calculated that the P-T conditions are 445~747.66 ℃ and 0.64~0.95 GPa for Kyanite sequence and 445~681 ℃ and 0.3~0.8 GPa for andalusite sequence. The andalusite sequence isn抰 a normal evolution progeny of metamorphism. The forming of kyanite sequence was probably related to an arc-continent collision event during the late Paleozoic, and the andalusite sequence may be produced by uplifting of the medium-pressure rocks and extensive intrusions of the collision-related granites.