The characteristics of the structure, strain and kinematic vorticity of the Wulian detachment fault zone, Shandong Peninsula, China  

作　　者：Jinlong NI Junlai LIU Yujie SUN Xiaoxiao SHI Shen LI 

机构地区：[1]Shandong Provincial Key Laboratory of Depositional Mineralization and Sedimentary Minerals, College of Earth Sciences and Engineering, Shandong University of Science and Technology, Qingdao 266590, China [2]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China [3]Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China [4]Cores and Samples Center of Land & Resources, China Geological Survey, Langfang 065200, China

出　　处：《Science China Earth Sciences》2019年第9期1399-1415,共17页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 41172089);the Natural Science Foundation of Shandong Province (Grant Nos. ZR2018MD010, ZR2017PD001);Key R & D Plan of Shandong Province (Grant No. 2017CXGC1602)

摘　　要：As one of the vital tectonic units of the Wulian Metamorphic Core Complex(MCC), the Wulian detachment fault zone(WDFZ), which developed in the Jiaodong peninsula, separates the lower plate of the ultrahigh pressure(UHP) metamorphic rocks in the Sulu orogenic belt from the upper plate of the early Cretaceous Zhucheng basin and the basin basement. The fault zone generally strikes NNE with a dip in the west along the southern portion of the MCC and strikes NE with a dip in the WNWalong the northern portion. The fault zone displays a wavy-tile-shaped extension on the plane, principally composed of the fault breccias and mylonite and transits downward to the mylonitic gneiss. As a whole, the detachment fault zone shows a top-towest or a WNW extension. By calculating the harmonic mean, we obtain a Flynn index K of 0.98–2.0, and the mean value is approximately 1.35 in the fault zone. According to the polar Mohr construction, the extensional crenulation cleavage, the RS/θ,and the quartz C-axial fabric methods, we acquire mean kinematic vorticity values of 0.64–0.97, 0.76–0.93, 0.6–0.92, and 0.63–0.98 with mean values of 0.83, 0.80, 0.78 and 0.86, respectively, for mylonite and promylonite. The strain measurement results and the kinematic vorticity values indicate that the WDFZ is a normal ductile shear zone developed in the extensional setting.The kinematic track shows that the kinematic vorticity value decreases gradually from the NW to the SE as a whole. A simple shear dominates in the middle and upper parts of the shear zone, which is reflected by a higher vorticity value(>0.75, up to 0.98),a low thinning rate and a lower K value. In contrast, toward the footwall, the pure shear is increased significantly, showing a lower vorticity value(<0.70, low to 0.64), a relatively high thinning rate and a higher K value. Combined with the geotectonic background, the development and evolution of the WDFZ should respond to lithospheric thinning and the destruction of the North China Craton(NCC). As a result, the WDFZ cAs one of the vital tectonic units of the Wulian Metamorphic Core Complex(MCC), the Wulian detachment fault zone(WDFZ), which developed in the Jiaodong peninsula, separates the lower plate of the ultrahigh pressure(UHP) metamorphic rocks in the Sulu orogenic belt from the upper plate of the early Cretaceous Zhucheng basin and the basin basement. The fault zone generally strikes NNE with a dip in the west along the southern portion of the MCC and strikes NE with a dip in the WNWalong the northern portion. The fault zone displays a wavy-tile-shaped extension on the plane, principally composed of the fault breccias and mylonite and transits downward to the mylonitic gneiss. As a whole, the detachment fault zone shows a top-towest or a WNW extension. By calculating the harmonic mean, we obtain a Flynn index K of 0.98–2.0, and the mean value is approximately 1.35 in the fault zone. According to the polar Mohr construction, the extensional crenulation cleavage, the RS/θ,and the quartz C-axial fabric methods, we acquire mean kinematic vorticity values of 0.64–0.97, 0.76–0.93, 0.6–0.92, and 0.63–0.98 with mean values of 0.83, 0.80, 0.78 and 0.86, respectively, for mylonite and promylonite. The strain measurement results and the kinematic vorticity values indicate that the WDFZ is a normal ductile shear zone developed in the extensional setting.The kinematic track shows that the kinematic vorticity value decreases gradually from the NW to the SE as a whole. A simple shear dominates in the middle and upper parts of the shear zone, which is reflected by a higher vorticity value(>0.75, up to 0.98),a low thinning rate and a lower K value. In contrast, toward the footwall, the pure shear is increased significantly, showing a lower vorticity value(<0.70, low to 0.64), a relatively high thinning rate and a higher K value. Combined with the geotectonic background, the development and evolution of the WDFZ should respond to lithospheric thinning and the destruction of the North China Craton(NCC). As a result, the WDFZ c

关 键 词：Wulian STRAIN intensity Kinematic VORTICITY MYLONITE DETACHMENT fault zone 

分 类 号：P[天文地球]