Dakendaban Group from the Erlangdong area, northern margin of the Qaidam Basin（NQB）, contains Early Paleozoic rock assemblage. The deformation feature and timing of the Dakendaban Group are still overlooked. We report the occurrence of L-tectonites with strong elongate lineation, weakly developed or undeveloped foliation. Detailed structural analysis of the L-tectonites can provide important information on tectonic evolution of the NQB. Two stages of deformation were observed. The D1 deformation was dominated by sinistral strike-slip shearing with thrust component, whereas the D2 deformation occurred as a lateral strike-slip with normal faulting component. Moreover, the D1 deformation resulted in the formations of L and LS tectonites. Mineral elongation lineation in the L tectonites plunged to the SE（around 142°）at 2°～54°, which was consistent with the extending direction of the North Qaidam tectonic belt. LA-ICP-MS zircon dating yields Early Paleozoic ages of 457 Ma and 406 Ma for the Ltectonites and undeformed andesitic sub-volcanic rocks that intruded into the L tectonites, respectively. Therefore, deformation timing of the L tectonites can be restricted to between 457 Ma and 406 Ma. The fabric analysis of quartz and feldspar suggested the deformation temperature of the L tectonites ranges from 380 ℃ to 420 ℃ with corresponding depths of 13～14 km. Detailed deformation analysis and petrographic studies in addition to the temporal framework of the Early Paleozoic magmatism, this paper concluded that the protoliths of the L and LS tectonites may be Early Paleozoic granites generated by the northward subduction of the Proto-Tethys Ocean. The sinistral strike-slip shearing with a extending direction similar to that of the NQB, locally occurred as a result of the oblique collision between Qaidam-East Kunlun Block and Qilian Block. Meanwhile, arc igneous rocks in middle crust level extruded to surface, and granites deformed to be isolated L tectonites, which was caused by a better mechanical than the other rocks due to their homogeneous compositions.
Da Liangchao Niu Manlan Li Xiucai Han Yu Wu Qi Yan Zhen Zhao Qiqi. Tectonic deformation characteristics of the L tectonites in Erlangdong area at the northern margin of Qaidam Basin and its geological significance[J]. Chinese Journal of Geology, 2017, 52(4): 1038-1057.