NE–SW-trending Hepu–Hetai dextral shear zone in southern China: Penetration of the Yunkai Promontory of South China into Indochina

The NE–SW-trending Hepu–Hetai shear zone extends for about 480 km along the boundary between Guangdong and Guangxi provinces in the southern part of South China. Field mapping and kinematic analyses indicate that the zone is characterized by dextral ductile strike-slip deformation, with an estimated displacement along the fault zone in excess of 500 km. Studies of synkinematic phengite and gas–liquid inclusions in quartz within mylonite suggest that the ductile shear deformation occurred under medium temperature/pressure conditions of the greenschist facies, and 40Ar/39Ar analyses of muscovite yield ages of 213–195 Ma. Based on these data and Late Paleozoic–Mesozoic paleogeographic data for southern China, we propose that the Hepu–Hetai shear zone originated via the penetration of the Yunkai Promontory of South China into Indochina during the Triassic.