COALIFICATION HISTORY OF THE YANGSHAN COALBEARING FORMATION IN THE EASTERN DABIESHAN TECTONIC ZONE

The metamorphism history of the coals in the Lower Carboniferous Yangshan coal-bearing formation is investigated comprehensively using the methods of the geological history analysis and EASY%R_o numerical modeling.It is shown that the coalification of the Yangshan coals was completed during two geological history stages,i.e.,the middle Hercynian tectonic cycle and the middle-late Yanshanian one.The rank of coking coal was achieved at the end of the first stage under the deep burial coalification derived from the lower palaogeothermal current,and the metaanthracite was acquired at the end of the secondary stage through the thermal metamorphism led by the higher palao-geothermal current.In the northern Dabieshan tectonic zone,a cooling basin seemed to occur during the middle Hercynian cycle and a heating basin might be developed during the middle-late Yanshanian one.