Early Mesozoic geotectonic processes in South China
XU Xian-bing1, ZHANG Yue-qiao2, JIA Dong1, SHU Liang-shu1, WANG Rui-rui1 (1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, Jiangsu, China; 2. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081)
South China experienced intense tectonic deformation and magmatism in Early Mesozoic, which resulted in profound change of the geodynamic regime. The processes and settings of the early Mesozoic geotectonic processes have long been a subject of controversy. Based on a summarization of previous research achievements, this paper deals with tectono-sedimentary layers, Early Mesozoic tectonic deformation styles and magmatic sequence, with the purpose of distinguishing between Indosinian and early Yanshanian tectonic events as well as their geological effects. It is shown that the Indosinian tectonic event occurred in Middle-Late Triassic (245～225Ma) and was featured by nearly EW-trending fold-and-thrust belts and NE-NNE striking ductile shear zones, which were dynamically related to the Triassic collision between the South China Block and the North China Block along the Qingling-Dabie orogenic belt and also to the subduction and accretion of plaeo-Tethys oceans along the southern margin of the South China Block. The basement of the Caledonian folded zone in eastern South China was intensely rejuvenated, and crustal melting occurred particularly in the Shiwan Mountains-Yunkai Mountain-Wuyi Mountain tectonic zone and Xuefeng area. Early Jurassic (205～190 Ma) marks an era of quiescence of magmatic activity in South China, whereas late Early Jurassic (190～180 Ma) was characterized by A-type granite emplacement and bimodal volcanic activity along the WE-trending Nanling belt. Early Yanshanian tectonic event commenced around 170 Ma in late Middle Jurassic, which caused the formation of a ～1300-km-wide, NE-NNE-trending fold-and-thrust system in South China. Crustal thickening and crust-mantle interaction led to the remobilization of Cathaysian Block and induced intense magmatic activities, with the development of a volcanic arc in southeastern China. This event was related to the low angle subduction of an oceanic plate under the South China Block, which led to a subsequent series of late Mesozoic intracontinental tectonic processes and magmatic activities.
【Fund】： 国家自然科学重点基金资助项目(40634022);; 国家科技专项(SinoProbe-08)资助
【CateGory Index】： P542.2
【CateGory Index】： P542.2