Petrology and Ar-40/Ar-39 isotopic ages of blueschists in Gangmar, centralQiangtang, northern Tibet

The petrology and mineral assemblages of blueschists in the Gangmar, centra l Qiangtang, northern Tibet were examined, which indicates that the metamor phic condition is high-pressure low-temperature, In this note, we reported the Ar-40/Ar-39 dating results of glaucophane from two blueschist samples. Their apparent ages are (275.0+/-1.3) Ma and (287.6+/-2.3) Ma and similar i sochron ages are (275.0+/-0.9) Ma and (282.4+/-0.8) Ma, respectively. These isotopic datings show the high-pressure metamorphism occurring in Lower Pe rmian. The ages also coincide with the evolution of Palaeo-Tethys ocean in Late Palaeozoic.