Geochemistry And Paleo-environmental Implications Of The No.4 Coal In Pingshuo Mine,Shan Xi Province

The Pingshuo Mine is located in the north of Ningwu Coalfield and subordinated to Shuozhou City,Shanxi Province.The coal-bearing strata in the study area include Benxi Formation,Taiyuan Formation and Shanxi Formation.The Taiyuan Formation thickness is 72.90 ~ 125.14 m,with an average of 107.65 m.The main available coal seams in the area are No.4,No.9 and No.11 coal.The Taiyuan Formation shows the characteristic of regression in general,and successively deposited on tidal flat,salt water peat swamp,brackish water peat swamp,lagoon,delta,and peat swamp facies from bottom to top.The No.4 coal samples are collected from the top of Taiyuan Formation.The major element oxides,trace elements and minerals were analyzed by X-ray fluorescence(XRF),inductively coupled plasma mass spectrometry(ICP-MS)and LTA-XRD in combination with Siroquant software,and were studied using the theoretical knowledge of coal petrology,mineralogy and geochemistry.The No.4 coal in the Pingshuo Mine is mainly a low/medium-ash,medium/high-volatile,low-moisture and low-sulfur.The sulfur is mainly organic sulfur.Vitrinite reflectance data(Ro=0.70%)indicate a gas coal rank.The No.4 coal in the Pingshuo Mine characteristically is abundant in kaolinite and followed by beohmite.In addition,it is low in siderite,rutile,anatase,apatite,hexahydrite,goyazite,florencite,arsenopyrite and quartz,which are only detected in individual samples.The No.4 coal is rich in copper,Ga,Se,Hg,Sr,Zr and Pb compared with Chinese coal,while the content of Lithum,Co,Ni,Ge,As,Rb,Sb,Cs and Ba is depleted.The REY content of No.4 coal varies widely.The light rare earth elements enrichment is the main contributors to total rare earth elements.And compared with LREY,HREY has more organic affinity.Lithium and Ni mainly be associated with silicate and clay minerals.Zinc,Wolfram,Cu and Co have strong affinity sulfur and mainly occur in sulfide and sulfate.Thallium,Sb ? Mo mainly be associated with sulfide.Indium has a good correlation with metal elements(Ti,Fe,Ca,Mg),which indicating that it may be associated with minerals containing such metals.The No.4 coal-forming micro-environments is terrestrial,humid,hypoxicoxygen-poor.From bottom to top,humid climate turns to arid,leading to an increase in the salinity.That results in enrichment of climatic significance elements.