Tectono-Thermal Evolution Of Northern Kuqa Depression And South Tien Shan

The(U-Th)/He and fission-track thermochronometry are benefited for studying the low-temperature tectono-thermal evolution of basins and mountains.The low temperature thermochronology has been used to study the tectono-thermal evolution of Kuqa river area in the Western Kuqa Depression,and the uplifting events and the latest uplifting time of South Tien Shan are still controversial.In this paper,the Mesozoic-Cenozoic outcrop samples from the western Kuqa Depression are used to study the tectonic-thermal evolution of the western Kuqa Depression,revealing three uplift events in this area: Early Cretaceous(140~110Ma)period,due to the assembly of the Lhasa terrane on the southern margin of the sub-plate,there is an erosion of 2 km;during the period of the late Cretaceous(70~40Ma)the uplift event is smaller with the effect of the long-range effects of the Lhasa plate and Kohistan-Dras island arc accretion.Since the Miocene-Pliocene period(~10Ma),the study area has undergone a rapid uplift event with erosion thickness of 2.5 km,which is closely related to the long-range impact of the Indo-EUrasia plate collision.The study of low-temperature thermochronology in the northern Kuqa Depression found that the apatite fission track and(U-Th)/He ages in the western part were smaller than those in the east,and the uplift time in the western Kuqa depression was earlier than that in the eastern part,which is maybe related to the rotation collision activity of the Taree block.The apatite He ages is between 9.9 Ma with 4.6 Ma in the western Kuqa Depression,much smaller than the age of the strata,revealing the time of the latest uplifting event in the South Tien Shan is Miocene to Pliocene period.The cooling temperature is 60°C and the erosion thickness of the stratum is 2.5km.The latest tectonic uplifting events(since the Miocene)in the South Tien Shan area match the time of mature oil and gas injection of the Tubei 2 structural belt on the northern Kuqa Depression.This tectonic movement has made the fault an advantageous drainage system,and it has a big influence on hydrocarbon accumulation in the Dabei area.