Study on geochemical characteristics of rare earth elements from coal in Ningwu Coalfield

Rare earth elements in coal have important research significance for indicating the source and reflecting the sedimentary environment， and they also have the potential for industrial use in some regions.In order to determine the enrichment degree of rare earth elements in Late Paleozoic coal of Ningwu Coalfield， the content of rare earth elements was measured by inductively coupled plasma mass spectrometry.The results of stepwise chemical extraction with X-ray fluorescence spectrum， X-ray diffraction， and Tessier Five-state Method on the distribution patterns， material sources， and occurrence states of middle and rare earth elements were discussed.The results show that rare earth elements in Ningwu Coalfield are slightly enriched，showing the distribution characteristics of high in the north and low in the south.The rare earth element Eu in each coal seam shows obvious negative anomaly， which indicates the source background of terrigenous clastic replenishment.The La/Yb-∑REE diagram is used to analyze sedimentary sources， mainly sedimentary rocks and granite，and the sources may come from the ancient land of Yinshan in the north.The overall light and heavy rare earth fractionation is not obvious，but the overall performance is that the influence of seawater is weakened and the degree of fractionation is reduced.The content of rare earth elements in coal is positively correlated with ash and other elements such as Al， Si， Fe and Mn， indicating that terrigenous debris is the main source of rare earth elements.The results of stepwise chemical extraction show that the occurrence state of rare earth elements in coal is dominated by aluminosilicate bound (74%) and organically bound (18%)， as the reducing conditions favor the enrichment of rare earth elements， and the enrichment of rare earth elements from coal of Taiyuan Formation is also related to pyrite.