Multiphase Tectonic Processes in the Mesozoic and Formation of Early Regional Geomorphic Pattern in the Qilian Orogenic Belt, Northeastern Tibetan Plateau

Abstract

Conventional orogenic settings are largely confined to plate boundaries and their immediate vicinity. However, there is growing recognition that deformation of the continental lithosphere may extend for considerable distances away from active plate boundaries. The Mesozoic Qilian orogenic belt occupies a key position in East Asia and thus is important to consider when interpreting intracontinental deformation there. To determine when and how the North Qilian orogenic belt developed, multiple sets of samples collected from the Dahuang Mountain of the North Qilian orogenic belt were analyzed for apatite (U-Th)/He and zircon (U-Th)/He thermochronology. The results show that the study area experienced multiphase tectonic exhumation events that took place in the Early-Middle Triassic (250–235 Ma), Middle-Late Jurassic (170–150 Ma), and Early Cretaceous (130–110 Ma). This study reveals that the generation deformation and stress distribution in the Dahuang Mountain fold-fault system have the characteristics of temporal–spatial migration from N to S. Results indicate widespread, continuous exhumation and deposition in the Qilian Mountain due to multiplate interaction since the Mesozoic, persisting till at least late Miocene. Multiphase intracontinental deformation is driven by stresses at plate boundaries, with lithosphere serving as stress pathway.