The Evolution Of Late Paleozoic Basins In North Margin Of North China Block And The Coupling Relationship Between Basin And Range

The Evolution of Late Paleozoic Basins in North Margin of North China Block and the Coupling Relationship between Basin and RangeZHOU an'chao (Dopt. of geology, Northwest University,Xi'an, 710069)AbstractThe late Paleozoic coal-gathering basins in North margin of North China Block consist of Daqingshan basin in Inner Mongolia, Xinglong basin and Pingquan basin in Hebei, Nanpiao basin in west Liaoning, etc. from west to east. The basins are closely adjacent to the south side of Inner Mongolia orogehic belt. In them, the Permo-Carboniferous coal-bearing series are parallel unconformity to the lower Paleozoic Cambrian-Ordovician sedimentary strata, which are dominated by carbonate. The formation, sedimentary insertion and evolution of basins were controlled by the plate tectonic processes of Inner Mongolia orogenic belt. Therefore, it provides us a good place for researching an orogenic belt and basin-range coupling relationship, being of great significance during studing on the continental dynamics.Based on the theories of plate tectonics and the continental dynamics as an academic advisor, the two representative basins (Daqingshan basin and Nanpiao basin) are studied. The mobilism views and the sedimentation analysis are emphasized during researching. Meanwhile, a comprehensive analysis has been used when we considered the relationship between the formation, sedimentary insertion of two basins and the processes of Inner Mongolia orogenic belt. Some conclusions are listed as follows:l.The late Paleozoic coal-gathering basins in North margin of North China Block came into the ground of compressional structure, which was affected by the strong subduction from north continental margin of North China Block to southMongolia micro-plate. With the plate tectonic evolution of Inner Mongolia erogenic belt, the attribute of the basins varied from fault and down-warped basins, which is in the ground of late Paleozoic North China craton basin in late Carboniferous, early stage of early Permian to foreland basins in middle and late of early Permian and late Permian. So the conclusion can be reached that the basins were composite overlap basins.2. The paleo-current measurement of sand and conglomerate, conglomerate source analysis, sand skeleton-grain type and the analysis of its quantity ratio obtained from the two basins indict that the terrigenous denudation lies in the northto the basin, and mother rock assemblage in land-source area is regularly variable, which has been demonstrated that the Permo-Carboniferous denudation in the north to the basins started from lower Paleozoic Cambrian-Ordovician, then the middle and late Proterozoic sedimentary cover, to mainly the vast Archaeozoic metamorphic rock and intrusion granite. In the end of early Permian and late Permian, the intermediate-acid lava erupted in The Inner Mongolia erogenic belt is also one important type of source rock. So the plate tectonic processes resulted in the different mother rock assemblage in land-source area.3.In the two basins, twelve volcanic-event sedimentary sequence could be decided by the 34-39 sedimentary event layers in Permo-Carboniferous coal-bearing series, and the selected trace element value or ratio in different layers varies regularly. Furthermore these layers could be well correlated each other. The detail lithology, petrochemistry and REE(rare earth element) analysis for the volcanic rocks shows that the volcanic clast in the late Paleozoic basins derived from volcanics in Inner Mongolia erogenic belt, which were mainly formed by the intermediate-acid materials erupted in C2- PI. The volcanic mater were transported into basin by the atmosphere current conveying and preserved very well, which provides a new proof for the precise contrast of coal-bearing series in late Paleozoic coal-gathering basins in North margin of North China Block and also provides an evidence for the study on coupling relationship between basin and range.4.1n late Carboniferous, under the ground of compressional structure formed by...