Three Dimensional Exhumation Process of the Greater Himalayan Complex above the Main Himalaya Thrust

The Greater Himalayan Complex (GHC) is characterized by high-grade (up to granulite facies) metamorphic rocks exhumed from the middle to lower crust, widespread migmatites from extensive anatectic process and high-temperature ductile deformation, suggesting that the Himalayan orogen is a “hot” collisional orogen. For a long time, the southward exhumation of the GHC was assumed to occur between the Main Central Thrust (MCT) and the South Tibet Detachment (STD) at ~24‒10 Ma. However, our previous studies in the GHC revealed the widespread presence of sub-horizontal ductile detachment with orogen-parallel stretching lineation in the upper part of the GHC, which can be traced from the Purang area in the western Himalaya to the eastern Namche Barwa Syntaxis. The U‒Pb ages of metamorphic zircon rims and Ar/Ar cooling ages of mica and hornblende indicate that the orogen-parallel extension in the GHC is asymmetric: initiated first in the central GHC and moved faster eastward (28‒26 Ma in the Nyalam and Jilong areas), but migrated slower westward (22 Ma in the Purang area). The lateral flow along the orogen-parallel detachments continued to 13‒11 Ma, coeval with the activation of the MCT and STD.