Study On The Deposition Process Of 4# Coal Seam In Hujiahe Mine Field

Based on Binchang mining area in Huanglong Jurassic coal field and Hujiahe mine field of existing geological data and the basis of the predecessors' research results,we synthesized coalfield geology,sequence stratigraphy,sedimentology,petrology,structural geology and other research methods,combined with field observation and indoor analysis,taking deposition process and coal accumulating laws as the main direction,summed up the Hujiahe deposition evolution process of 4#coal seam in mining field,analyzed the coal control factors,concluded coal accumulating pattern,and forecast the coal bearing property.The survival stratum of Hujiahe mine field is less,the preservation of stratum sequence is not complete,only keeping the sequence I of the third-order sequence.The coal-bearing stratum of Yan'an group can be divided into two position cycle,4#coal seam is in the bottom of the first cycle,the coal-bearing stratum of mine field main developed for inland river deposition,the river flood swamp,cutoff lake and swamp on the flood plain are the main coal accumulating environment of 4#coal seam.Deposition gradually evolved into coal,due to the ancient warm and humid climate environment,a large number of coal plants,the favorable ancient geographical environment and good stability of ancient structure,Yan'an group of Hujiahe mine field formed a single,huge thickness of 4#coal seam.To a certain extent,ancient geography has an effect on the formation of coal seams beyond ancient climate and ancient structure,and even beyond ancient plants,so ancient geography can be said the first controlling factor of the formation of 4#giant coal seam.According to the coal lithofacies ancient geographic map of the first period of Yan'an group,the position cross-section map of 4#coal seam in east-west and north-south,we induces the evolutionary process and the coal accumulating pattern of 4#coal seam and draw the 4#coal seam thickness contour map in Hujiahe mine field.The analysis found that the rich coal belt distributes in the southeast of the mine field and extends to the north and the west and the coal-rich center is located in the center and southwest of the mine fields.On the research of 14 drilling analysis of 4#thick coal seam in rich coal belt development area of mine field,we found that the thickness of 4#thick coal seam in rich coal belt development area and stratum thickness of the first paragraph of Yan'an group is obviously positive correlation.In the near of the ancient river channel in the west of the mine field,the 4#huge coal seam appeared bifurcation,thinning and pinching.The Fuxian group and the Yan'an group of the region flown through by the ancient channel were all missing,forming a coal barren area.These laws will provide a good theoretical basis for the coal mining and the coal-bearing prediction in the future.