Abstract: Tectonic activity is a fundamental discriminant factor in site assessment for radioactive waste. The tectonic activity of geological repository of radioactive waste which is located at Aqishan-Yamasu in the East Tianshan was evaluated through model studying the uplift and exhumation history by the apatite fission track dating. The result shows that apatite fission track pool-agedata range from 81.7 to 51.4 Ma which recorded a cooling event of the East Tianshan during the Late Cretaceous to Eocene, which is consistent with a tectonic uplift and denudation event in the Late Cretaceous in the Tianshan. The mean track lengths range from 13.60±0.11 to 14.36±0.10 μm with the standard deviations of 0.98 ~1.22 μm, which suggests that most tracks didn’ t experience thermal annealing process after they were formed. Based on evaluated geothermal gradient, the mean exhumation rate in the East Tianshan during the Late Cretaceous to Eocene was calculated to reach 270~580 m/Ma. The geological data and further temperature-time modeling of apatite was conducted, indicating that an exhumation event existed from the Late Cretaceous to Eocene (84~49 Ma); after 50 Ma, the crust of the east Tianshan has been in a steady state, and the Cenozoic tectonic activity in Aqishan-Yamansu area has become significantly weaker than other area of Tianshan. The study shows that the geomorphologic features of present Tianshan inherit that from the Late Cretaceous, and weak tectonic activity conforms to the tectonic requirements of geological disposal of radioactive waste.

Key words: tectonic activity, geological disposal of radioactive waste, Aqishan-Yamansu, apatite fission track, uplift and exhumation