Geochemical Characteristics and Coal-forming Environment of Coal Seams in the Aga Mining Area of the Liupanshui Coalfield
Taking 13 minable coal seams from 7 coal exploration boreholes in the Aga mining area of the Liupanshui coalfield as the research object,the industrial parameters,major and trace elements of the coal seam samples in the study area were tested.The geochemical characteristics of the coal seams in the Aga mining area were evaluated,and the coal-forming environment of the mining area was explored.The results indicate that the coal seams in Aga mining area have alternating coal quality characteristics of low moisture,medium high ash content,low medium volatile matter,and high medium high ultra-low sulfur coal.The content of SiO2,CaO,and TiO2 in the main components of coal seams is relatively high,with SiO2 being 7 times that of national coal,CaO being 5.6 times that of national coal,and TiO2 being 4.4 times that of national coal;Compared with the average of Chinese coal,trace elements in coal are more abundant in Ni,Co,Ga,Zr,and U,while Li,Be,Ge,Tl,Cs,Hf,and Ba are relatively depleted.The standardized rare earth element distribution curve of chondrites in the coal mining area shows that the distribution patterns of rare earth elements in each coal seam are similar,showing a wide and gentle"V"shaped curve with high left and low right.The light rare earth distribution curve segment is"right leaning",and the heavy rare earth distribution curve segment is relatively"flat",with a high degree of light and heavy rare earth element fractionation;The total amount of rare earth elements vertically increases with the burial depth of coal seams;δCe ranges from 0.93 to 1.01,with an average of 0.96,indicating a slight negative Ce anomaly;δEu ranges from 0.58 to 0.80,with an average of 0.72,showing a significant negative Eu anomaly.The study also found that the Nb element content(average 20.80μg/g)in the 29#and 30#coal seams at the bottom of the mining area is 5.6 times the world average for coal,the Zr element content(215.85μg/g)is 6.0 times the world average for coal,and the REE content(332.79μg/g)is 4.8 times the world average for coal.This indicates that the Nb,Zr,and REE are more abundant in the coal seams at the bottom of the mining area.In addition,the coal ash composition index and the triangular end element analysis of the coal ash composition reveal that the coal-forming environment changes from an environment with shallow water and strong hydrodynamics but weak reducibility in the land source area to an environment far away from the land source area with deep water and weak hydrodynamics but strong reducibility.Based on comprehensive analysis,it is believed that the coal seams in the Aga mining area are mainly composed of terrestrial sedimentary clastic rocks,which are less affected by the marine environment.The material source is neutral rocks,and the coal formation period is in an environment of oxidation reduction transition.
Aga mining areacoal geochemistrycoal-forming environment
NETL
NSTL
万方数据
