Three-dimensional extrusion model of the Great Himalaya slice

Abstract：The Greater Himalayan Complex (GHC) , as the metamorphic core of the Himalayan orogen, shows a “hot” collisional orogen characterized by high-grade (up to granulite facies) metamorphic rocks exhumed from the middle-lower crust, widespread migmatites from extensive anatectic processes and high-temperature ductile deformation. A three-dimensional tectonic model for extrusion of the GHC has been proposed based on the discovery of widespread orogen-parallel ductile extension. It is suggested that extrusion dynamic processes of the GHC are as follows： (1) partial melting in 45-36Ma resulting in the weak and hot middle crust, (2) orogen-parallel gravitational collapse in 28-26Ma, (3) ductile thrusting since > 26 Ma and (4) ductile extrusion resulting from the formation of MCT and STD during 23-17Ma .