川东北地区构造-热演化探讨--来自(U-Th)／He年龄和Ro的约束

Tectonothermal Evolution of the Northeastern Sichuan Basin:Constraints from Apatite and Zircon(U-Th)/He Ages and Vitrinite Reflectance Data

利用镜质组反射率和磷灰石与锆石的(U-Th)/He年龄一起模拟了川东北地区三叠纪以来的构造-热演化特征。结果表明早三叠世的热流值在51～66mW/m2,自晚三叠世至白垩纪随盆地性质由前陆盆地演化为陆内坳陷盆地,热流缓慢降低直至现今的44.5mW/m2。但在晚白垩世—古新世时期受燕山晚期构造运动的影响,热流有一个微弱增高的现象。同时,磷灰石和锆石的He年龄揭示了川东北地区大致在晚白垩世期间开始隆升且抬升剥蚀量较大。因此,磷灰石和锆石的(U-Th)/He年龄可以揭示后期详细的冷却历史。

The tectono-thermal evolution since Triassic for the northeastern Sichuan Basin was modelled by using combined vitrinite reflectance and apatite and zircon （U-Th）/He dating methods. Corresponding to a transformation of the foreland basin during the Late Triassic to the interior cratonic basin in the Cretaceous, the paleo-heat flow was 51-66 mW/m2 during the Early Triassic. It decreased gradually to the present-day＇s 44.5 mW/m2. However, the heat flow increased a little at the late Cretaceous and Paleoene due to the late Yanshanian tectonic movement. At the same time, the apatite and zircon （U-Th）/He age dating revealed an uplifting of northeastern Siehuan Basin at the Late Cretaceous and the erosion could be up to more than 3000 m. The apatite and zircon （U-Th）/He ages can also provide the details of cooling history for the study area.