Deformation and tectonic evolution of the Karakorum fault, western Tibet

Abstract：The deformation features, age, tectonic evolution and tectonic role of the Karakorum fault (KF) have long been controversial. In the Ayila Ri’gyü area in the southeastern segment of the KF, dextral sheared mylonite and mylonitized gneiss-granite are exposed along the fault. Microstructural study indicates high-temperature, dextral shear features, accompanied by the generation of synkinematic leucogranite. The U-Pb ages recorded by synkinematic crystalline zircons imply that：the KF formed at least before 23－25 Ma and its continuous deformation at least continued to ~12 Ma, when the deformation was accompanied by rapid uplift of the Ayila Ri＇gyü Range and initiation of the Gar basin. Integrated analysis indicates that the growth process of the KF might be a process of northwest-directed propagation and the result of continuous India-Eurasia collision. The cumulative displacement amount is at least 280 km ａｌｏｎｇ the fault， and ａｎ average long-term slip rate is ~11 mm/a ｏｎ ｔｈｅ ｆａｕｌｔ. Rigid block kinematic analysis suggests that material of the Qinghai-Tibet Plateau was extruded toward ~108°N ａｔ a rate of 16.2 mm/a after ~23－25 Ma.