Geochemistry characteristics and indicative significance of rare earth elements in coal from Juhugeng coal district, the Muli coalfield in Qinghai Province

The rare earth elements, major elements, microcomponents and industrial components in the coal seam and its roof and floor were determined by ICP-MS, X-ray fluorescence spectrum, optical microscope and industrial analysis of coal.According to the results, the content, geochemical characteristics and distribution patterns of rare earth elements were comprehensively analyzed.The modes of occurrence and genesis of rare earth elements in coal were discussed.The results show that the average content of REE is 23.01×10^-6 in the No.1 coal of the Juhugeng mining area.LREE/HREE mean value is 3.38, indicating that the light rare earth elements are more abundant than the heavy rare earth elements.In the top and bottom mudstone of the lower coal, rare earth elements are relatively enriched, and the total amount of rare earth elements is much higher than that of coal, with an average value of 8.6 times that of coal.The distribution mode of rare earth elements in the roof and floor is similar to that in the coal.With the influence of the change of water body in the coal accumulation swamp and the later hydrothermal action, the rare earth content is slightly different.The rare earth elements in the coal are closely related to the continental source rocks.In the coal, Eu negative anomaly is obvious, and the structure preservation index (TPI) versus gelation index (GI) diagram shows that the coal-forming environment is mainly a reducing environment, which is consistent with the coal-forming environment indicated by Eu anomaly.The negative Ce anomaly may be related to the strong reduction environment.In coal, rare earth element REE is positively correlated with ash content (R=0.481), and positively correlated with SiO₂ (R=0.652), indicating that rare earth elements in the No.1 coal in the Juhugeng mining area coexist in inorganic state.The content of rare earth elements in the mudstone of roof and floor is positively correlated with clay minerals, among which the content of illite is most closely related to the enrichment of rare earth elements.