The Qilian Caledonides on the north margin of the Qinghai-Xinjiang (Tibet) Plateau were formed by convergence and collision of the Alxa plate, Qilian microplate and Qaidam-East Kunlun microplate. The North Qaidam ultrahigh-pressure (UHP) metamorphic belt, lying between the Qilian and Qaidam-East Kunlun plates was formed between 495 and 440 Ma by deep subduction of the Qaidam-East Kunlun continental crust after the South Qilian oceanic subduction beneath the Qilian microplate and formation of the North Qaidam arc volcanic belt. The UHP belt was exhumed by a process of "oblique extrusion" during transformation from "normal" to "oblique" intracontinental subduction between the Qiliabn microplate and Qaidam-East Kunlun plates. Exhumation began at 470 ~ 460 Ma and was completed by 406 ~ 400 Ma. Exhumation structures are well-preserved in the UHP rocks and record extensive retrograde metamorphism.