Geological analysis and FT dating of the large-scale right-lateral strike-slip movement of the Red River fault zone

摘要

Tectonically, the large-scale right-lateral strike-slip movement along the Red River fault zone is characterized at its late phase with the southeastward extension and deformation of the Northwestern Yunnan normal fault depression on its northern segment, and the dextral shear displacement on its central-southern segment. Research of the relations between stratum deformation and fault movement on the typical fault segments, such as Jianchuan, southeast Midu, Yuanjiang River, Yuanyang, etc. since the Miocene Epoch shows that there are two times dextral faulting dominated by normal shearing occurring along the Red River fault zone since the Miocene Epoch. The fission track dating (abbreviated to FT dating, the same below) is conducted on apatite samples collected from the above fault segments and relating to these movements. Based on the measured single grain's age and the confined track length, we choose the Laslet annealing model to retrieve the thermal history of the samples, and the results show that the fault zone experienced two times obvious shear displacement, one in 5.5 ±1.5 MaBP and the other in 2.1 ± 0.8 MaBP. The central-southern segment sees two intensive uplifts of mountain mass in the Yuanjiang River-Yuanyang region at 3.6—3.8 MaBP and 1.6—2.3 MaBP, which correspond to the above-mentioned two dextral normal displacement events since the late Miocene Epoch.