Geochemical Characteristics Of Trace Elements In The NO.3 Coal From Jinyuan Mine

In this paper,the abundance,distribution,modes of occurrence,and enrichment mechanism of minerals and trace elements in the Late Permian NO.3 coal from Jinyuan Mine,Tengnan Coalfield,Shandong Province were studied based on the theoretical knowledge of coal geology,mineralogy,coal chemistry,geochemistry,and statistics,as well as the analysis technology of optical microscope,scanning electron microscopy with an energy dispersive X-ray spectrometer?SEM-EDS?,low temperature ashing?LTA?,X-ray diffraction?XRD?,Siroquant quantification system,X-ray fluorescence spectrometry?XRF?,inductively coupled plasma mass spectrometry?ICP-MS?,and mercury analyzers.The results indicate that NO.3 coal of Jinyuan mine is low ash,low sulfur,high calorific,and medium-high volatile.Under the optical microscope,the vitrinite content in coal is the highest.The content of the inertin group is significantly lower than that of the vitrinite group.The content of the chitin group is the lowest.The mineral is as follows quartz,kaolinite,ankerite and calcite.In addition,a trace of pyrite,microcline,sodium feldspar and rutile was also found by the scanning electron microscopy.The mineral composition that responds to the volcanic event mainly includes aluminosilicate minerals,sharp-angled and embayed quartz,and fissure-filling carbonate minerals.The abundances of major elements in the coal benches,compared to the average values for Chinese coals.CaO and MgO are close to Chinese coal,but other major oxides?SiO₂,Al₂O₃,Fe₂O₃,TiO₂,K₂O,Na₂O,P₂O₅ and MnO?are lower than those of average Chinese coal.The SiO₂/Al₂O₃ indicates that there is a large amount of free SiO₂ in the No.3 coal seam of Jinyuan Coal Mine.The Al₂O₃/TiO₂ weight ratios indicating that the relevant parent rock is felsic.The calculated CIA indicating extreme weathering and hot and moist depositional environment.Therefore,according to the sedimentary environment of the coal-forming period,combined with the characteristics of the palaeotopography and paleo-current water,it is determined that the Mengshan mountain possibly is a region to provide sediment-source.Compared with the average Chinese coals,the contents of Be,Co,Ni,Zn,Zr,Nb,Mo,Hf,Ta,W,Pb and Bi in the coal seam shows depleted?CC<0.5?and the contents of Li,Sc,V,Cr,Cu,Ga,Rb,Sr,Ba,Th,U and Hg in the coal seam shows normal?0.5<CC<2?.The harmful elements in No.3 coal seam of Jinyuan Coal Mine are Be,V,Ba,Sr,Cr,Cu,Mo,Pb,Th,U and Hg.In the JY-1,JY-9 and JY-12 samples,the content of harmful elements was obviously higher than the Chinese value and the world value.The correlation analysis shows that Be,V,Cr,Cu,Mo,Pb,Th,U and Hg occur in silicate minerals,and V,Mo and Th exhibit certain inorganic and organic affinity.Pb and Hg also occur in sulfur minerals,and Ba and Sr occur in carbonate minerals.In terms of geochemical characteristics of rare elements,Jinyuan coal exhibits a weak negative?Eu anomaly,which is closely related to the control of source rocks in the Tertiary area.The coal seam is affected by high temperature hydrothermal fluid,which will present?Eu positive anomaly,which offsets the negative anomaly characteristics inherited from the source rock,and finally shows a negative anomaly with very weak?Eu.In general,harmful elements in the studied samples were mainly derived from volcanic ashes and multi-stage hydrothermal fluids.Tengnan coalfield is the main distribution region of volcanic rocks at late Paleozoic era.Pyroclastic rock probably originate from the southeastern part of the North China.The magmatic rocks in Tengnan coalfield derived from the third stage of the Cretaceous magmatic activity.