华北与扬子两板块的拼贴方式与扬子北缘古生代盆地应变特征

洋板块的消减及其后两侧陆块的拼合,是板块构造作用的两个不同阶段.分隔扬子与华北两板块的古秦岭洋,于晚志留世向北单边俯冲关闭.根据秦岭造山带内发育的大型推覆体构造组合及其配置关系,推覆体岩片内的变质相倒置、推覆岩片内应变标志物的显微构造特征和应变参数的测量及南秦岭大型泥盆纪—石炭纪前陆盆地的厘定,均一致确证了华北板块与扬子板块于420～380Ma至340～320Ma之间以仰冲兼右行剪切的方式碰撞拼贴.对扬子北缘古生代盆地应变标志物有限应变测量研究表明,扬子北缘古生代盆地从南向北可划分为4个应变量不同的应变区:无应变或弱应变区、强应变区、中等强度应变区和强应变区.应变区划分的构造学意义:a)扬子克拉通北缘是寻找古生代油气藏的有利地区;b)南秦岭造山带是晚加里东和海西-印支运动形成的复合山链.通过对扬子北缘古生代盆地构造变形特征,包括褶皱特征、逆冲-推覆构造特征、应变标志物的应变特征分析,估算南秦岭造山带的构造缩短量为918.8km. 

MATCHING MODE OF NORTH CHINA AND YANGTZE PLATES AND STRAIN CHARACTERISTICS OF THE PALEOZOIC BASIN IN THE NORTH EDGE OF THE YANGTZE PLATE

The subduction of ocean plate and the following amalgamation of continent plates besides, are the two different stadges of plate tectonic movement. The ancient Qinling ocean separating Yangtze and North China plates subducted and closed to the north during the Late Jurassic. Large nappe structure composition and its arrangement, metamorphic facies invert in nappe sliver, microstructural characteristics of strain sign in nappe silver and the measure of strain parameter, and the determination of large Devonian-(Carboni-)ferous foreland basin in South Qinling, all these together identifies that, the North China and Yangtze plates collided and amalgamated with subduction and dextral shear from 420-380 Ma to 340-320 Ma. The research on finite strain of strain sign of Paleozoic basin in the north edge of Yangtze plate indicates that, the Paleozoic basin in the north edge of Yangtze plate can be divided, from south to north, into 4 different strain zones:strainless or weak strain zone, strong strain zone,middle strain zone and strang strain zone. The Tectonic significance of strain zone division is:a)the northern edge of Yangtze craton is the favo-rite zone for Paleozoic oil and gas accumulation;b)the South Qinling orogenic belt is the combined mountain chain resulted from late Caledonian and Hercynian-Indosinian movement. Based on the strain characteristics analysis on the structural deformation charateristics, including fold charateristics, obduction-nappe structure characteristics and strain characteristics of strain sign, of the Paleozoic basin in the north edge of Yangtze plate, the tectonic shortage of South Qinling orogenic belt is roughly calculated to be 918.8 km.