Initiation Timing of the Jiamusi–Yitong Fault Zone in NE China  

作　　者：WEN Quanbo LIU Yongjiang LIANG Chenyue Li Weimin SHAO Yilun ZHANG Qian ZHANG Duo LIU Xinyue 

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130061,China [2]Key Lab of Submarine Geosciences and Prospecting Techniques,MOE,Institute for Advanced Ocean Study,College of M arine Geosciences,Ocean University of China,Qingdao 266100,China [3]Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China [4]Key laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Land and Resources,Changchun 1300615 [5]Department of Geology,University of Otago,Dunedin 9016,New Zealand

出　　处：《Acta Geologica Sinica(English Edition)》2019年第5期1580-1590,共11页地质学报（英文版）

基　　金：funded by the National Key R&D Program of China (Grant No. 2017YFC0601300–01);973 Program (Grant 2013CB429802);NSFC (Grant 41102140,41303175)

摘　　要：The NE-striking Jiamusi-Yitong fault zone(JYFZ) is the most important branch in the northern segment of the Tancheng-Lujiang fault zone. The precise shearing time of its large-scale sinistral strike-slip has yet to determined and must be constrained. Detailed field investigations and comprehensive analyses show that strike-slip faults or ductile shear belts exist as origination structures along the western region of Yitong Graben. The strike of the shear belts trend to the NE-SW with steep mylonitic foliation. The zircon U-Pb dating result for the granite was 264.1±1 Ma in the ductile shear belt of the JYFZ. The microstructural observation(rotated feldspar porphyroclasts, S-C fabrics, and quartz c-axis fabrics, etc.) demonstrated the sinistral shearing of the ductile shear zones. Moreover, the recrystallized quartz types show a transitional stage of the subgrain rotation toward the recrystallization of the grain boundary migration(SR-GBM). Therefore, we suggest that the metamorphic grade of the shear zone in the ductile shear zones should have reached high greenschist facies conditions, and the deformation temperatures should approximately 450-500°C, which is obviously higher than the blocking temperature of muscovite(300-400°C). Hence, the ^40Ar/^39Ar isochron age of muscovite from ductile shear zones should be a cooling age(162.7±1 Ma). We infer that the sinistral strike-slipping event at the JYFZ occurred in the late Jurassic period, and it was further inferred from the ages of the main geological events in this region that the second sinistral strike-slip age of the Tancheng-Lujiang fault zone occurred during the period of tectonic movements in the Circum-Pacific tectonic domain. This discovery also indicates the age of the Tancheng-Lujiang fault zone that stretches to northeastern China. The initiation of the JYFZ in the late Jurassic is related to the speed and direction of oblique subduction of the west Pacific Plate under the Eurasian continent and is responsible for collision during the Jurassic periThe NE–striking Jiamusi–Yitong fault zone（JYFZ） is the most important branch in the northern segment of the Tancheng–Lujiang fault zone. The precise shearing time of its large–scale sinistral strike–slip has yet to determined and must be constrained. Detailed field investigations and comprehensive analyses show that strike–slip faults or ductile shear belts exist as origination structures along the western region of Yitong Graben. The strike of the shear belts trend to the NE–SW with steep mylonitic foliation. The zircon U–Pb dating result for the granite was 264.1±1 Ma in the ductile shear belt of the JYFZ. The microstructural observation（rotated feldspar porphyroclasts, S–C fabrics, and quartz c–axis fabrics, etc.） demonstrated the sinistral shearing of the ductile shear zones. Moreover, the recrystallized quartz types show a transitional stage of the subgrain rotation toward the recrystallization of the grain boundary migration（SR–GBM）. Therefore, we suggest that the metamorphic grade of the shear zone in the ductile shear zones should have reached high greenschist facies conditions, and the deformation temperatures should approximately 450–500°C, which is obviously higher than the blocking temperature of muscovite（300–400°C）. Hence, the 40Ar/39Ar isochron age of muscovite from ductile shear zones should be a cooling age（162.7±1 Ma）. We infer that the sinistral strike–slipping event at the JYFZ occurred in the late Jurassic period, and it was further inferred from the ages of the main geological events in this region that the second sinistral strike–slip age of the Tancheng–Lujiang fault zone occurred during the period of tectonic movements in the Circum–Pacific tectonic domain. This discovery also indicates the age of the Tancheng–Lujiang fault zone that stretches to northeastern China. The initiation of the JYFZ in the late Jurassic is related to the speed and direction of oblique subduction of the west Pacific Plate under the Eurasian continent and

关 键 词：Origin structures sinistral DUCTILE shear belt microstructures ^40AR /^39Ar DATING Jiamusi-Yitong Fault Zone 

分 类 号：P54[天文地球—构造地质学]