中、上扬子北部盆-山系统演化与动力学机制

中国南方中生代经历了中国大陆最终主体拼合的陆缘及其之后的陆内构造演化。晚古生代末期,在秦岭—大别山微板块与扬子板块之间存在向西张口的洋盆,即勉略古洋盆。中三叠世末期开始,扬子板块相对于华北板块发生自南东向北西的斜向俯冲碰撞作用,扬子北缘晚三叠世至中侏罗世发育陆缘前陆褶皱逆冲带与前陆盆地系统。晚侏罗世至早白垩世,中国东部的大地构造背景发生了重要的构造转变,中、上扬子地区处于三面围限会聚的大地构造背景。在这种大地构造格局下,中、上扬子地区晚侏罗世至早白垩世发育陆内联合、复合构造与具前渊沉降的克拉通内盆地系统。自中侏罗世末期开始,扬子北缘前陆带与雪峰山—幕阜山褶皱逆冲带经历了自东向西的会聚变形过程及盆地的自东向西的迁移过程和收缩过程。扬子北缘相对华北板块的斜向俯冲导致在中扬子北缘的深俯冲及超高压变质岩的形成。俯冲之后以郯庐断裂—襄广断裂围限的大别山超高压变质地块在晚侏罗世向南强逆冲,致使扬子北缘晚三叠世至中侏罗世前陆盆地被掩覆和改造。

Evolution and geodynamic mechanism of basin-mountain systems in the northern margin of the Middle-Upper Yangtze

South China underwent the continental margin tectonism during the final Chinese continental collision and the intracontinental tectonism hereafter in the Mesozoic.In the Late Paleozoic,there was an oceanic basin opened to the west,which is called the Mianlue ocean,between the Qinling-Dabie plate and the Yangtze plate.From the latest Middle Triassic,the Yangtze plate obliquely subducted and collided towards the North China plate northwestward,and in the Late Triassic till the Middle Jurassic,the continental margin foreland fold and thrust belt and the foreland basin system were developed in the northern Yangtze.The tectonic setting of East China took an important change in the Late Jurassic and Early Cretaceous,and the Middle-Upper Yangtze was surrounded and contracted by mountains on three sides.Under this kind of tectonism,in the Late Jurassic and the Early Cretaceous,intracontinental combination and superposition structures and intracratonic basin with foredeep system were formed in the Middle-Upper Yangtze.Beginning at the latest Middle Jurassic,the northern Yangtze foreland belt and the Xuefengshan-Mufushan fold and thrust belt were assembled from east to west,and the intracratonic basin migrated and shrank from east to west.The oblique collision of the Yangtze plate towards the North China plate resulted in the deep subduction of the northern Yangtze and the formation of ultra-high pressure metamorphic rocks.The thrust of the Dabie ultra-high pressure metamorphic block along the Xiang-Guang fault and Tanlu fault after the subduction brought about the covering and deforming of the Late Triassic and Middle Jurassic foreland basin in the northern Yangtze.