Mesozoic tectonic evolution history of the Tan-Lu fault zone, China: Advances and new understanding
ZHANG Yue-qiao1, DONG Shu-wen2 1. Department of Earth Sciences, Nanjing University,Nanjing 210093, Jiangsu, China; 2. Institute of Geological Mechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
The authors put forward a new chronological evolution model of the Mesozoic kinematic history of the Tan-Lu fault zone, which is boiled down to "two movement periods and five development stages". The first movement period corresponds to the Triassic to earliest Early Jurassic "Indosinian Movement", characterized by amalgamation between the North China Craton and the Yangtze block and collisional orogeny. During this movement period, the Tan-Lu fault zone experienced two stages, i.e. the first and second stages. The first stage (240-220 Ma) was a transition strike-slip stage, when the strike-slip movement of the fault zone was restricted to a transform zone between two ultra-high pressure (UHP) metamorphic belts. The Xu-Huai orocline on the western side of the Tan-Lu fault zone was formed by westward ductile extrusion of the Sulu UHP metamorphic belt as a consequence of the deep subduction of the Yangtze block beneath the North China Craton. The second stage (220-190 Ma) was a left-lateral strike-slip stage. During this stage, the Xu-Huai orocline was displaced southward about 145 km and then was absorbed an E-W-striking thrust system in the hinterland area of the Dabie orogenic belt. Northward propagation of the left-slip motion made the Tan-Lu fault zone go through the whole of North China and Northeast China. The second movement period corresponded to the Middle-Late Jurassic to Paleocene "Yanshan Movement", and the tectonic history of the Tan-Lu fault zone was closely associated with the evolution of the active continental margin of East Asia. The fault zone during this movement period underwent three stages, i.e. the third, fourth and fifth stages. The third stage (Middle-Late Jurassic to earliest Early Cretaceous) witnessed compressive strike-slip motion, accompanied by the lithospheric and crustal thickening of the eastern North China Block and formation and development of the Tan-Lu fault system. The fourth stage (Early Cretaceous) saw crustal extension and intracontinental rifting, resulting in collapse and thinning of the thickened lithosphere of North China. During the fifth stage (Late Cretaceous to Paleocene), dextral strike-slip motion predominated and a number of pull-apart basins formed along and at both sides of the Tan-Lu fault zone. The paper systematically describes the Mesozoic development history and geological features of the Tan-Lu fault zone and its specific role played in the tectonic evolution of the East Asian continent.