再论长江中下游转换构造结——基于结构、属性、过程与动力学的思考

Further discuss on the Middle and Lower Reaches of the Yangtze River transitional tectonic node: Thinking based on structures, properties, process and dynamics

长江中下游转换构造结现象经典、结构复杂、过程清晰,是中国东部中生代以来有时空联系的多种构造的集中展现。该构造结的主要内涵包括:1) 3大构造类型:大陆造山带(大别造山带)、陆缘剪切带(郯庐断裂带)和陆内热点(下扬子热点);2) 3大应力方式:华南和华北两大板块近SN向的挤压,太平洋板块作用下东亚陆缘剪切和中国东部伸展背景下的下扬子热点;3) 3大转换机制:特提斯与太平洋两大构造域的构造体制转换,中生代从SW-NE向到近S-N 向再到SE-NW 向的挤压方向转换,区域性的挤压应力作用向伸展应力作用的应力方式转换。可见,长江中下游转换构造结的结构、属性和演化过程完整记录了中生代以来变化有序的构造演化和丰富多样的构造属性,展示了区内复杂连续的动力学系统背景下的深部过程与浅表响应,揭示了全球性特殊的岩石圈动力学过程。

The Middle and Lower Reaches of the Yangtze River transitional tectonic node has classical geological phenomena, complex structures and clear tectonic process, which is a concentrated display of various structures of time - space connection since the Mesozoic in eastern China. The main contents of this transitional tectonic node include: 1) three tectonic types: continental orogenic belt (the Dabie orogenic belt), continental margin shear zone (the Tanlu fault belt) and intracontinental hotspot (the Lower Yangtze hotspot), 2) three stress modes: the compressional stress of SN trending between the South China and North China plates, the east Asian continental margin shear under the subdution of the Pacific Plate and the Lower Yangtze hotspot under the extensional background of eastern China, 3) three major transformation mechanisms: tectonic regime transformation from the Tethys to the Pacific tectonic domain, the compression direction shift from SW-SE to near S-N to SE-NW trending in the Mesozoic, and stress mode transformation from regional compression to extension. Obviously, the structures, properties and process of the transitional tectonic node of the Middle and Lower Reaches of the Yangtze River full records the sequential changes in tectonic evolution and the variety of structural properties, shows the deep process and shallow response under complicated dynamic background, and reveals the special global lithospheric dynamics process.