Geochemistry Of Trace Element In Aluminous Mudstones In Coal Measure Of The Huainan Coalfield

Rare earth and other valuable elements could be enriched in coal and certain rocks in coal measures.The Huainan coalfield is one of the most important energy base in East China,which is rich in coals.It is adjacent to the Tanlu Fault easternly.Yanshanian magmatic activity in the area is strong,the coal bearing strata are the products of the marine continental interaction sedimentary environment.The special geotectonics,magmatic activities and sedimentary environment may lead to the enrichment of rare elements in some rocks of coal measures strata.The study of rare elements in coal and coal measures strata can provide scientific basis for comprehensive and sustainable utilization of coal resources in this area.Taking the Guqiao Coal Mine of Huainan coalfield as the research object,the samples of underlying aluminous mudstone in 4-1 coal seam of Lower Shihezi Formation were collected.The mineral composition,major elements,trace elements and rare earth elements contents of the samples were analyzed by optical microscope,X-ray diffractometer,X-ray fluorescence spectrometer and inductively coupled plasma mass spectrometer.Based on the theories of mineralogy,geochemistry and ore deposit,this paper study the geochemical characteristics of the aluminous mudstone,and discuss the sedimentary environment and material source,the resource potential of associated rare elements is comprehensively evaluated.The results show that:(1)The mineral composition of the aluminous mudstone in Guqiao Mine is mainly composed of kaolinite,siderite and quartz,occasionally contain dawsonite(GQ03).The widespread existence of kaolinite indicates that the sedimentary basin is far away from the provenance area.Under microscope,the basement of aluminous mudstone is microcrystalline and cryptocrystal line,and oolitic,agglomerate and clastic mineral particles are dispersed in the matrix.There are different forms of kaolinite,quartz and siderite.Nodular siderite and oolitic kaolinite show that the ore is syngenetic.(2)Compared with the background values of Chinese continental crust,the aluminous mudstones are enrich in Al2O3,Fe2O3,and TiO2,while depleted in SiO2 and alkali metal oxides.Regarding trace elements,the aluminous mudstones are extremely enriched in Ag,highly enriched in Cd,and enriched in Li,B,Cr,Ga,Ni,Ge,Zr,In,Hf,and Bi.The contents of Sc,V,Zn,Sn,W and Pb in the mudstones are at normal ranges,however,the contents of Be,Co,Cu,Sr,Nb,Mo,Cs,Ba,Ta,Th,U and rare earth elements are depleted.(3)Sample GQ01 has the highest REY content,LREY is more enriched than HREY,and Ce and Eu show negative anomalies.Among sample GQ02 and GQ04,MREY is slightly enriched,HREY is obviously enriched,REY fractionation is obvious,GQ02 is Ce and Eu positive anomaly,GQ04 is negative Ce positive Eu anomaly.Sample GQ03 is the least REY content,the distribution curve is nearly horizontal,HREY is slightly enriched,Ce and Eu are both positive anomalies.La/Y values indicate that the distribution of rare earth elements is affected by the pH value of medium.Ce anomaly shows that although the samples of aluminous mudstones come from the same coal mine,their sedimentary microenvironment is still quite different.(4)Geochemical indexes such as B and Ga contents,La/Y and Sr/Ba indicate that the aluminous mudstone is the product of weak acid weak alkaline continental sedimentary environment affected by fresh water.Sr/Cu shows that the paleoclimate conditions were relatively dry and hot,and geochemical indicators such as U/Th,V/Cr and Ce anomalies show that the medium conditions are weak reduction weak oxidation.Al2O3/TiO2,Zr/Hf and Eu anomaly show that the source rock of aluminous mudstone in Guqiao Mine is intermediate acid rock.(5)The Al2O3/SiO2 value of the Lower Shihezi Formation aluminous mudstone in Huainan coalfield does not reach the cut-off grade,so it is suitable for general refractory clay.Ga in the aluminous mudstone can meet the industrial recovery standard,while the associated elements such as V,B,Co,Ni,Nb,Zr and REY do not reach the cut-off grade.Figure[10]Table[3]Reference[137]...