Apatite fission track dating evidence for tectonic movement of Yarlung Zangbo Thrust Zone

Fission track geological chronology is an effective method of study on tectonic movement of fault zone. Apatite fission track (AFT) dating analyses of 9-apatite and 4-zircon samples collected from Lhasa to Langkazi, ～70-km-long in SN provide an understanding of the age and the uplifting of both sides of the Yarlung Zangbo Thrust Zone (YZTZ) in this work. The AFT ages range from ～37 to 14 Ma, indicating the time of major tectono-thermal events, i.e. the continent-continent collision along the YZTZ. Based on the relationship between the AFT ages and the sample elevations, there were two tectonic active periods: ～37–20 Ma and 20–14 Ma. In the first period the tectonic event did not bring on differential uplifting. Rapid differential uplifting with rapid cooling, resulting from thrusting, took place in the second period. The vertical displacement was ～1020 m and total ～2.9 km of overburden has been removed from the present-day surface since cooling below ～100°C began. The maximum cooling and denudation occurred at a rate of ～7°C/ Ma and ～207 m/Ma respectively since ～14 Ma. The zircon fission track analysis demonstrates that the temperature of tectono-thermal events did not exceed 310°C.