Northern Lhasa thrust belt of central Tibet: Evidence of Cretaceous-early Cenozoic shortening within a passive roof thrust system?

The Lhasa and Qiangtang terranes of Tibet collided following Late Jurassic-Early Cretaceous consumption of oceanic lithosphere along the intervening Bangong suture zone. This continental collision led to the development of the south-directed, northern Lhasa thrust belt that is exposed ∼1200 km along strike in central Tibet. We conducted geologic mapping and stratigraphic and geothermochronologic studies in the Duba region of the northern Lhasa terrane, located ∼250 km northwest of the city of Lhasa. In the Duba region, granites were emplaced into the mid-crust between 139 and 121 Ma and subsequently exhumed and juxtaposed against Cretaceous strata between 105 and 90 Ma in the footwall of an interpreted passive roof thrust system. We suggest that this structural style dominates the Cretaceous-early Cenozoic evolution of the northern Lhasa thrust belt and provides an explanation for the scarcity of basement rock exposures in the Lhasa terrane despite >50% upper crustal shortening. Furthermore, we highlight similarities between the collision-related northern Lhasa and Tethyan Himalayan thrust belts, both of which are bound by sutures and associated with underthrusting of lower plate lithosphere.