2 TYPES OF PRECAMBRIAN HIGH-GRADE METAMORPHISM, INNER-MONGOLIA, CHINA

Archaean and Proterozoic granulite facies complexes of Inner Mongolia differ in lithological association, tectonic style, mineral assemblage and metamorphic P-T path. A nearly isobaric cooling path for Archaean high-grade metamorphic rocks is suggested by reaction textures and ge othermobarometry. Early Proterozoic metamorphic rocks show nearly isot hermal decompression. Archaean metamorphism may have been caused by ma gmatic accretion, whereas early Proterozoic metamorphism suggests a ma jor continental thickening event followed by exhumation.