Evidences of Syn-Extensional Emplacement of Yiwulüshan Pluton and Its Geological Significance
LI Gang, LIU Zheng-hong, XU Zhong-yuan, DONG Xiao-jie, SHA Qian, WANG Wan-qiong, WANG Xing-an, ZHANG ChaoCollege of Earth Sciences, Jilin University, Changchun 130061, China
The Yiwulüshan pluton is an important part of the Yiwulü metamorphic core complex. Due to its deformation and relationship with surrounding tectonic belts, the Yiwulüshan pluton is determined as the syn-extensional granite. The pluton emplaced along or parallel to ductile shear zone as a bedding-sill, which modifies previous view that the pluton caused by magma emplacement under compressed environment. The emplacement time of both the Yiwulüshan pluton and the Jianlazishan pluton is about 160 Ma, which implies intensive crustal extension occurred in the Yiwulüshan and Yanshan region in late Middle Jurassic and the tectonic pattern of the northern part of North China had been transformed in Middle Jurassic period. There were two extensional stages in the area in the Mesozoic. The earlier occured in the Late Jurassic and accompanying with the emplacement of the Yiwulüshan pluton. The later extension occurred in the Early Cretaceous and resulting in the formation of the Waziyü detachment fault.