Early Proterozoic high-pressure metamorphism in the Wutaishan

The detailed study of metamorphism from the original North Jingangku Format ion of the Wutai Group indicates three metamorphic evolutionary stages: ini tial tectonic burial metamorphism (M1) probably related to collision betwee n island are and continent, subsequent high-pressure metamorphism (M2) exte nding 0.8 similar to1.4GPa down to a depth of 42km from the peak metamorphi sm in response to crustal tectonic thickening, and isothermal decompression process (M3) as a result of rapid exhumation. A clockwise P-T evolutionary path is similar to the P-T-t path of the typical orogenic belt.