Trace Elements And Associated Ore In Handan-Xingtai Coalfield

The study of the concentration, distribution and mode of occurrence of trace elements in coals is one of the hot-points in present day.This paper discusses the coal property, mineralogy, trace elements, and the relationship between the extractive and trace elements of the coal in Handan-Xingtai mining area. The samples were examined using coal analysis, fluorescence microscope (MVP—III), scanning electronic microscope (SEM), ICP-MS, gas chromatography (GC) and gas chromatography-mass spectrography(GC-MS). Some of the author own opinions and new apprehend are expounded.Coal-bearing strata belong to Permo-carboniferous period. The main coals are bituminous coal, and there are some anthracite and carbonite. The grade of coal is very complex in this area. The high rank coal and the low rank coal distribute banded from west to east.The main lithotypes of coal are vitrain and clatrain, and the durain is very little. The bright coal and semibright coal are main marco lithotypes. The most part of maceral group is vitrinite, next is inertinite, and exinite is least and the modes of occurrences are stratiform, dispergated, filling in cell cavities and fractures.Compared with the concentrations of trace elements in coals of USA and China, the average concentrations of Be, Cr, Ga, Pb and Th are higher, and Zn, As, Se, Sb and Ge are lower, and Co, Ni and Cu are close in Han-xing coal mining areas. Base on the EF (Enrichment Factor), Li, Be, Ga, As, Se, Zr, Mo, Cd, In, Sn, Sb, Cs, REE, Hf, W, Pb, Bi, Th, U and Au enriched in the study areas.The distributions of the trace elements are: the concentrations of them in the same coalbeds but in different mines are different, and in the same mines but in different coalbeds are also different. Moreover, the concentrations change along with vertical in the same coalbeds, that is to say, they are higher in gangues, roof rocks and floor rocks than in coals. In addition, the concentrations in the coals nearby roof rocks are higher than those nearby floor rocks.The correlation coefficient between concentration of trace elements and percentage of shows that: Mo and Ni are significant negative correlations; W, Zn and Zr are moderate positive correlations, Co, Cd and Sn are moderate negative correlations; Sc, Be and Ba are low positive correlations, Se, Li, In and Gr are low negative correlations. Be, Cr, Cs, F, Ga, Li, Rb, Ti, V, Ni, Sc, Ti, and REE usually occur in clay minerals, Mn, Fe, Sr, Zn, Co and Ba may mainly occur in carbonate minerals, and Cu, Pb, Zn, Fe, Co, Ni, As, Sb, Se, Mo, Hg, Ag, Ge, Tl and Mn occur in sulphide minerals.The samples are lack of Eu (δ_Eu<1) in rare earth elements (REE).The value of Th/U is higher in 2# coalbed (4.55) than 5# coalbed (3.35). The variation of w(Sr)/w(Ba) directs that the change of paleowater salinity can influence the distribution of the trace elements. The average concentration of Ga in the coals of 5# coalbed, Xingtai mine, is 32.07μg/g, and it is higher than industrial grade.The results of GC and GC-MS show that there is a negative correlation between the concentration of trace elements and the weight of extractives. The carbon preference index (CPI) and even preference (OEP), the value of Pr/C17 and Ph/C18 and methylphenanthrene index (MPI) indicate that the correlation between the concentration of trace elements and the maturity of organic matters is negative.The occurrences of trace elements in coal are complex. The characters of the terrigenous sediments controlled the concentration and distribution of trace elements. The variation of depositional environment caused the differences of concentration and distribution in the same coalbed but in different areas and horizons.