Control Of Trace Elements By Micro-grained Minerals In Coal In Yangquan Mining Area

Based on the analysis of the contents of trace elements and the types of micro-fine minerals,the control of micro-fine minerals on trace elements in coal is discussed in this paper,taking the No.8 coal(XJ-8)and No.15 coal(SJZ-15)of Xinjing Coal Mine in Yangquan Coal Mine in the north of Qinshui Coal Field as the research objects.The composition of microscopic coal rock and the minerals in coal were analyzed by optical microscope.Inductively coupled plasma emission spectrometer(ICP-OES)and inductively coupled plasma mass spectrometer(ICP-MS)were used to detect the contents of major and trace elements in coal respectively.The mineral types in raw coal samples and low temperature ash samples were analyzed by X-ray diffraction(XRD).The morphology characteristics and some trace elements of micro-fine minerals were observed by Raman spectroscopy and SEM-EDS.Laser denudation plasma mass spectrometry(LA-ICP-MS)was used to study in situ trace elements of the target minerals.The research results are as follows:(1)Through macerals analysis of 32 coal samples from XJ-8 and SJZ-15,it was determined that the vitrinite was the main source of coal samples,accounting for 74.07%and91.97%,respectively.The average random reflectance of coal samples is 2.35%and 2.28%,respectively,which belongs to anthracite.(2)Compared with the trace element content in Chinese coal,the trace elements enriched in XJ-8 coal include Li,Zr,Nb,HF,Ta,Pb and Th,while the content of Li in SJZ-15 coal is not high,only slightly enriched in gangue and floor.The elements Li,Zr,Nb,Hf,Ta and Th in XJ-8 coal are positively correlated with the oxides of Al₂O₃,SiO₂ and TiO₂,indicating that they occur in minerals and originate from terrigenous detritus.The distribution pattern of REE in coal samples and non-coal samples(roof and gangue)is similar and left-leaning,and LREE is enriched,indicating that the main sources of REE in coal samples,roof and floor and gangue are consistent,indicating that REE is mainly controlled by the supply of terrestrial detrital.(3)Clay minerals such as kaolinite and nacrite are common in coal XJ-8 and SJZ-15,and albite is occasionally detected in coal.Common carbonate minerals are calcite;the main oxide minerals in coal are quartz and bauxite.Sulfide minerals include pyrite and pyrite;The main phosphate minerals are apatite;Sulfate minerals are mainly gypsum.In addition to the common minerals in the coal mentioned above,molybdenite,wollastonite,potash and other minerals were detected in some samples.The mineral structure and occurrence are diverse,including banded filling in the fissure of vitrinite or filament,filling in the cell cavity of organic matter and so on.(4)The results of in situ microanalysis show that the main trace elements of pyrite are As and Pb,followed by Co,Ni,Cu,Rb,Mo,Ag,Sn and Au.CO²⁺,Ni³⁺,Mo²⁺,Sn²⁺,Ag⁺,Au⁺,Pb²⁺plasma can usually replace Fe²⁺ions in crystals,and As^3-can replace S^2-to form isoimage substitution.Cu,Pb and Zn are cuprophilic elements,and Fe²⁺is not easily replaced by them.It mainly exists in the form of micro-fine mineral inclusions,and occurs on the surface of pyrite in the form of galena,chalcopyrite and sphalerite.