Thrusting And Exhumation Of The Kuqa Foreland Thrust Belt In Xinjiang Revealed By Low-temperature Thermochronology

"Coincidence mapping" is a new method of automated counting and analysis of fission tracks. Combined with other user’s feedback of this method, our controlling experiments indicating careful sample preparation is the crucial first step for getting ideal results. The experiments designed to test the consistent of results of this fully automated counting system obtain good results. However, we found that fully automated counting produces a relatively larger scatter compared to conventional track counting and manual correction is necessary for each individual sample. The manual correction and image-collection procedures significantly increases the time required to analyze a sample with the automated counting procedure compared to the conventional approach. As a whole, at present, the automated counting isn’t suitable for daily experiments.The results of systematic sampling and low-temperature thermochronology analysis of the Kuqa foreland thrust belt revealed important denudation event at 250Ma,160Ma, 100Ma and 30Ma in Tianshan from Mesozoic. This multi-stage denudation is linked to far-field effects resulted from the collision and accretion of terranes along the southern Asian continental margin.Studies on the Kuqa River cross-section recorded the Cretaceous thrust started at 110Ma in the Kuruli fault of Sidike tectionic belt then propagated to southern Fault F at 95Ma and to the Qiulitage tectionic belt at 86Ma. Ealiest coeval event in Baicheng area was recorded at 90Ma, hence implying the differentiation in the age of commencing of uplifting in east and west part of Kuqa thrust-fold belt.The activity of Jiesidelike Anticline and A’ge Fault around 50Ma represent the first stage of thrust and exhumation event in the Cenozoic.The exhumation revealed by thermal history modeling of granite in Kuqa area at 30Ma and the activation of fault in Baicheng at 27.8Ma imply the second one. The apatite fissition track age of 17.4Ma from Tiereke Spa profile and the active age of fault at 16.8Ma from Gong’an Coal profile revealed the third one.The apatite U-Th/He data from the F’fault in Baicheng area recorded the 1.8Ma and 0.25Ma, which is the fourth stage thrust denudation.