Enrichment Characteristics Of Trace Elements And Rare Earth Elements In Late Permian Coal From Puan And Qinglong Coalfield,Guizhou Province

Puan and Qinglong coalfield is rich in coal resources and one of the most important coal-produced bases in Guizhou province.With the vigorous promotion of the coal resources' reasonable exploitation and sustained usage,how to minimum the harmful elements emitted into the air during coal mining and burning processes and how to make full advantages of useful accompanying elements who are treated as potential resources in coal and coal ashes have already became the hot topic in coal geology and coal geochemistry.Therefore,it is necessary to prevent pollution and promote reasonable usage of coal by studying distribution and enrichment characteristic of Late Permian coal from Puan and Qinglong coal field.And it also will be helpful and significant for circular economic development of coal and theoretical reasearches.By targeting the Late Permian coal-bearing formation as the main object of study, this thesis has studied some major aspects of the coal respectively such as structures, constructons, coal structures, constructions, coal quality, concentrations and distributions of trace elements and REE,enrichment genesis and the enrichment ore-forming potential of accompanying elements with the applications of coal petrology, mineralogy, sedimentary and geochemistry. Now the specific research contents are listed as follows:1. Distribution and enrichment characteristics of the Late Permian coal measures.Compared to the concentrations of Guizhou and Chinese coal and combined with enrichment coefficients, the Late Permian coal from Puan and Qinglong coal field has relatively a higher concentration of trace elements, especially like Li?V?Cr?Ge?As?Nb?Mo?W and U, among them, a few elements' concentrations are even much more higer, such as Li?Ge?Ag?As?Mo?W and U etc. The researched area also has high REE's contents(205.17 ?g/g) and relatively enriches LREE when in comparsion with those elements in crust(150.68 ?g/g), sedimentary rock(135.37 ?g/g), Guizhou and Chinese coal(96 ?g/g?117.69 ?g/g). After combustion of those raw coal, the contents in ashes are further concentrated. In addition, according to the contents distribution and variation along the vertical orientation in a few samples from two groups of coal seam profiles, we discover that many elements are higher in surrounding rocks than those found in the corresponding coal seam.2.The analysis about the enrichment of ore-forming potential in accompanying elements in coal measures.On the whole, there are many elements(such as Li?V?Nb?Ga?Zr?Ag and U) whose contents are relatively high in the Permian coal measures and the enrichment degree roughly is : coal ashes > surrounding rocks > coal.Therefore, compared wih some elements' marginal and the lowest industrial grade, the concentrations of Nb in No.17 coal seam, Nb?Zr?V?Ga and U in coal ashes of Puan and Qinglong coal seams and Nb?Zr in surrounding rocks from Hongfa coal mine are mainly up to the available standards of initial exploitation in term of theory, with a view to the lowcost of exploration in coal ashes and surrounding rocks. However, the content of REO is lower than the corresponding available standards of exploitation. As a result, REO can not be used up to now.3.The causes for race elements and REEs' enrichment and the analysis about the sources of those elements in coal.The contents of REE(rare earth elements) in the Late Permian coal from Puan and Qinglong coal field are much higer than those in coralline and sea water; the REEs' distribution patterns in different coal seams are almost the same with each other and also similar with Emeishan basalt;the negative anomaly of Eu is evident. All of the above evidences consistently indicate that the resources of different coal seals' rare earth elements are the same, who have a closely connection with the terrigenous clastic rock. The relationships between ?REE and ash contents or accompanying elements also further suggest that the REE shares very close ties with inorganic constituent. Besides, the much more nearer to the provenance, the much more higher the coal'element content is.Therefore, the rare earth elements(REE) in the Late Permian coal from Puan and Qinglong coal field are deprived from the terrigenous clastic rock and the Emeishan basalt is the main parent rock.The elements like Li?Sc?V?Cr?Co?Ge?As?Nb?Mo?W?U are obviously enriched in the Late Permian coal from Puan and Qinglong coal field. Through the research, it is found that thatepicontinental elements who has a powerfu mobility, such as V?Cr?Co?Ni etc, are under the strictly control of the provision of Emeishan basaltic clast from the provenance. The sedimentary environment is also one of the factors that could influence the enrichment of some elements. For example, U?V?S and Mo are inclined to be limitedly enriched when the action of sea water becomes strong. Some elements like Li?Nb?Zr?Mo and U are consistently enriched who are affected by the sedimentation of synsedimentary volcanic ash. Furthermore, the low temperature hydrothermal activity after coal-forming peroid make coal seams, especially the bottom coal seams(C19?C26) are obviously enriched specific elements, such as As?Mo?U and W. All in all,the synsedimentary volcanic ash' sedimentation and the low tempperature hydrothermal activity are the main reasons for enrichment of the Late Permian coal from Puan and Qinglong coal field.Althoug their influences maybe not have the universality, whom usually appear in regional area,the significant influnces indeed exsit.