Thrusting of the North Lhasa Block in the Tibetan Plateau

Abstract

Abstract A huge thrust system, the North Lhasa Thrust (NLT), was discovered in the northern Lhasa block of the Tibetan Plateau based on geological mapping of the Damxung region and its vicinity, the Dêqên‐Lunpola traverse and the Amdo‐Bam Co profile. The NLT consists of the Dongqiao‐Lunpola thrust (DLT), the west Namco thrust (WNT) and the south Damxung thrust (SDT) and ductile shear zones, ophiolite slices and folds extending in a WNW direction. Major thrust faults of the NLT seem to merge into a single deep‐seated detachment of the upper‐crust and totally displaced southward as far as 100–120 km. Chronological analyses with 39Ar‐40Ar of plagioclase and hornblende, Rb‐Sr isochron of minerals and fission‐tracks of apatite from mylonite within the WNT yield ages of 174–173 Ma, 109 Ma and 44 Ma, showing 3 periods of thrusting in the north Lhasa block caused by subduction of the Tethys oceanic plate and the India‐Eurasia continental collision respectively.