科研之友
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摘要
The structure, properties, processes and dynamics of the south China continent have always been the focus among geologists. In this paper, the eastern part of the Qinghang tectonic belt was taken as the main research area. Based on detailed structural analysis, metamorphism and deformation research, chronology analysis and reflection seismic profile, the authors investigated several scientific problems in the eastern part of the south China continent. (1) The Jiangnan orogenic belt was formed by the "soft collision" between the Cathaysia plate and the Yangtze plate in late Proterozoic, which can be divided into three tectonic units: the southern margin of the Yangtze plate, the Yangtze-Cathaysia convergence belt and the northern margin of the Cathaysia plate. The Jiangnan fault belt and The Wuyishan- Suichang fault belt are the northern and southern boundary of the Jiangnan orogenic belt, respectively. (2) The Yangtze-Cathaysia convergence belt is composed of several small plates and suture zones. The convergence between them was progressive from south to north. It was shown as oblique subduction at first, followed by dextral strikeslipping, and the activity was concentrated in the middle at the latest. It began at about 900 Ma, reached its climax in 850~780 Ma and was closed completely at about 760 Ma. (3) The tectonic framework of the east of South China continent was established in the Mesozoic. The main structure was a series of NE-striking folds and thrust faults. A large number of imbricated thrusting nappe structures with thrusting movement from south to north originated from the middle-lower crust scale. (4) The regional extensional structures were widely developed in the east of the South China continent in late Yanshanian which led to the formation of“the South China thermal upwelling”. It developed typical sliding nappe structures in the Sinian strata. The large- scale magmatic activity, volcanic activity and large-scale hydrothermal mineralization took place at the same time. (5) The tectonic evolution of the South China continent is as follows: The peak of progressive convergence between the Yangtze-Cathaysia plate took place at about 850 Ma. Plates were closed completely and the Jiangnan orogenic belt was formed at about 760 Ma. Then the development of cover of South China continent began at 600 Ma. The Qinhang tectonic belt was affected by the southern structure and the remote effect of the north structures at 430 Ma and 220 Ma, respectively. Thrust nappe structure was widely developed at 160 Ma, while widespread extensional structures was developed at 140 Ma. The tectonic-magma-mineralization had close relationship. Then the Jiangnan belt continued to uplift and the South China became a thermo-upwelling.
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