The Main Control Factors Coal Accumulation And Favorable Area Selection Of Middle And Lower Jurassic In Southeastern Xinjiang

According to the existing characteristics and the reality of exploitation and utilization of coal resources in southeastern Xinjiang,the prominent problems in the study of coal resources distribution are searched by this paper.Based on the analysis of the basic geological conditions such as the distribution of coal-bearing strata and the theoretical basis of sedimentology,sequence,tectonics,coal geology and coal geochemistry,the sequence stratigraphy,stratigraphic correlation,depositional evolution,coal accumulation law and other key issues of the Middle and Lower Jurassic in southeastern Xinjiang are discussed by this paper.Through the identification of three secondary sequence interfaces and three third-order sequence interfaces,the Middle-Lower Jurassic is divided into five third-order sequences,and a correlation scheme of Jurassic strata between the southeast depression of the Tarim Basin and the western Chaixi area is established.In general,the Lower Jurassic Shalitashi formation corresponds to the Huxishan formation,the Lower Jurassic Kangsu formation corresponds to the Xiaomeigou formation,the Middle Jurassic Yangye formation corresponds to the Dameigou formation,the Taerga formation corresponds to the Shimengou formation;The upper Jurassic Kuzigongsu formation corresponds to the Caishiling formation and the Hongshuigou formation.The evolution of sedimentary environment of middle and lower Jurassic can be summarized as three stages: initial fault period,first coal accumulation period and depression period.The initial fault stage is characterized by two small grain-shaped faults,which are not controlled by Altun fault,and the basin is not controlled by Altun fault.Over the Altun Mountains area,the Minfeng sag is connected with the Tula basin,the Washixia depression is connected with the western Chaixi area,and the sedimentary center is located in the present Aljinshan area.During the first coal accumulation period,the fault activity changed from strong to weak,the water area expanded,and four coal accumulation centers were formed.In the depression period,the sedimentary area of the basin is enlarged,the basin floor is smooth,the Minfeng,Washixia sag,Toula,Chaixi is a unified lake basin,and the Great Altun Lake is formed.Finally,from the aspects of paleoclimate,paleoenvironment,sporopollen assemblage,coal facies,tectonic movement and sedimentary environment,the main controlling factors of coal accumulation in middle and lower Jurassic in southeastern Xinjiang are analyzed,and the space-time distribution law of coal-rich zone is defined.The main controlling factors and occurrence law of coal resources accumulation are analyzed.On the basis of the above,the optimal selection of favorable areas is carried out,the next exploration direction is analyzed,and five favorable exploration target areas are proposed,such as the Aixi-Alabasi suite,Hongliugou,Huangyangquan and two springs,eastern Buya,and the northern part of Mincan-2 well.It is expected to provide a scientific reference for the prediction of coal resources potential and the evaluation of exploration prospects in southeastern Xinjiang.