华北南部晚古生代陆表海的沉积充填、聚煤特征和构造演化

华北南部晚古生代煤系为海退型剖面,沉积环境演化为由陆表海碳酸盐—碎屑海岸、碎屑潮坪至被河流三角洲充填的半咸水海湾。晚石炭世中期华北南缘与秦岭—大别山区因拉张分离出现了陆表海,陆源碎屑自北向南的充填表明北方蒙古—西伯利亚板块向华北板块北缘的对接俯冲。沉积中心和聚煤作用随之自北向南迁移,因此在华北南部集中了丰富的煤炭资源。聚煤最有利的沉积环境是海退形成的滨海平原和河流注入浅水海湾形成的三角洲平原。煤变质带自本区中部向南递减表明三叠纪沉积中心向北迁移,表明华北南缘与秦岭—大别山地块以及华南板块的对接拼合时间可能发生在煤系形成之后至三叠纪以前,海西末期的可能性较大。

THE DEPOSITIONAL FILLING, COAL ACCUMULATION CHARACTERISTICS AND TECTONIC EVOLUTION OF THE LATE PALEOZOIC EPEIRIC SEA IN THE SOUTH OF NORTH CHINA

The coal system of Late Paleozoic in the south of North China presents a regressive section with the depositional environment evolutiom from epeiric seacarbonate-clastic sea coast through clastic tidal flat to brackish bay filled by river deltas. In Late Carboniferous the epeiric sea came into existence because of the extension of the south margin of North China and Qinling-Dabie mountain areas. The southward filling of terrigenous elastics verifies the convergent subduction of Mongolia-Siberia plate into the north margin of North China plate and the southward migration of deposition center and coal accumulation. The result of this is the concentration of abundant coal resources in the south of North China. The most favourable depositional environment for coal accumulation is the seashore plain formed by regression and the delta plain formed by the entering of rivers into the shallow bay. The reduction of the coal metamorphic belt from the center of the region to the south proves the northward migration of deposition center in Triassic and the fact that it is more likely that the convergent amalgamation of the south margin of North China and Qinling-Dabie massif and South China plate happened in Late Hercynian,after the formation of the coal system and before Triassic period.