The exhumation evolution of the Micang Shan-Hannan uplift since Cretaceous:Evidence from apatite(U-Th)/He dating
米仓山-汉南隆起白垩纪以来的剥露作用:磷灰石(U-Th)/He年龄记录

The apatite (U-Th)/He dating results of 13 granitic samples collected in Nanjiang-Nanzheng transect are used to systematically study Micang Shan′s exhumation and thermo-tectonic evolution. While taking into consideration of the influence of the sample′s cooling rates and crystal sizes on (U-Th)/He closure temperatures of respective apatites, this research also quantifies the effects of topography, heat conduction, advection and production on regional geothermal gradients. The inversion results reveal a period of rapid exhumation with an average rate of ~70 m/Ma in the southern sedimentary area of Micang Shan since about 50 Ma B.P., which removed above 3 km-thick sub-surface rock in the region; the Guangwushan Complex in the middle part of Micang Shan-Hannan Uplift experienced a fast exhumation event at ~90 Ma B.P. with an exhumation rate of >75 m/Ma; the northern Hannan Uplift was exhumed to the surface with a fast rate above 40 m/Ma before ~100 Ma B.P., and then slowly with an average exhumation rate of ~10 m/Ma. The whole research region, Micang Shan-Hannan Uplift experienced a very slow exhumation with an average rate of 10~25 m/Ma during 90~50 Ma B.P.