Geochemistry Of No.8 Coal And Its Relationship With Coal Metamorphism In Xishan Coalfield,Taiyuan

Xishan Coalfield in Taiyuan city is one of the major coking coal producing area in China,the coal-bearing strata in this region is mainly Late Paleozoic Carboniferous-Permian coal-bearing strata,and No.8 coal in Taiyuan Fromation is one of minable seams,though burial depth does not differ great,there is a big difference in metamorphic grade.Huyan mountain rock mass,located on the southwest side of the coalfield,has a crucial influence on the coal metamorphism of No.8 coal.Therefore,this paper mainly take the perspective of trace elements and rare earth elements,and discuss the distribution,modes of occurrence and enrichment reasons of trace elements and rare earth elements in order to understand the impacts of metamorphism and geochemical characteristics of trace elements and rare earth elements using the knowledge of coal mineralogy and geochemistry,and this will provide a theoretical basis for the efficient and clean use of No.8 coal.Main conclusions included:?1?Reflectances of No.8 coal in this area,with low moisture,low ash content and low-medium volatiles and high sulfur content,are in the range of 1.2%-2.0%.The coals are rich coal,coking coal,lean coal and meager-lean coal.The ash is mainly composited of Al₂O₃ and SiO₂.Lithotypes types of No.8 coal are bright coal;?2?Minerals in No.8 coal on the west side of Xishan coalfield are clay minerals,some samples contain small amounts of pyrite,quartz and calcite;samples on the east side are of much more types of minerals;?3?The trace elements indicating parameters show the forming environment of No.8 coal is influenced by seawater.The contents of harmful trace elements Co,Cu and Zn are higher.Li,V,Co,Cu,Zn,Ga,Rb,Cs,Zr,W and U are enriched in samples on the west side;Co,Cu,Zn and W are enriched in the samples on east part.The enrichment of Li,V,Cu,Ga,Zr,W and U primarily are influenced by parent rock,and with the influence of seawater,V,Rb and U enriched largely;enrichment of Zn is influenced by alkali,alkaline magmatism;enrichment of Co is controlled by sedimentary environment;Rb,Cs and Zr is enriched by Huyanshan rock mass,enrichment of Li,V,Co and U is controlled by temperature,migration temperature of Co is significantly greater than Li,V,and U;?4?The rare earth elements are often appeared in clay minerals and anatase.The geochemical parameters indicate LREE are enriched,HREE are loss,and the fractionation of rare earth elements is apparent.Coal-forming environment was affected by seawater evidently;distribution patterns of REE have nothing to do with the coal-forming and coalification process in low rank coal.