| Huainan Coalfield is the most important coal production base of East China. The abundant development of intrusive rocks in the coalfield constitutes a threat to safety mining. At normal coal-forming conditions, the concentration, distribution pattern of rare earth elements (REE) in coals are rather stable, however, at some areas where intrusive rocks were identified, the concentration, distribution pattern of coals REE could be more complicated. Therefore, we collected202samples including4intrusive rocks,196coal samples of10minable coal seams and2carbonaceous rocks after full investigation of the coal bearing sequences. The precision instruments such XRF, ICP-AES, ICP-MS, XRDand polarized-light microscope were used to fully investigate the physical characteristics and chemical compositions of coals and rocks and their relationship with REE.The results show that the intrusive rocks along coal bearing sequences upward correspondsa transition from acidic granite, intermediate diorite to basic gabbro.Major elements index (e.g. TiO2/Al2O3) and geochemistry parameters of REE like (La/Yb)N, Ce/Ce*and Eu/Eu*also show systematic variation with the evolution of intrusive magma, suggesting different geochemistry of intrusive rocks with the evolution of intrusive magma. The concentration of REE in coal samples that not affected by intrusive fluids fitted well into the normal distribution, and most of values are at between70and170μg/g; However, the REE concentration in coal roof and gangue was significantly higher, up to712and718μg/g, respectively; The intrusive coals seams of3,4-1and4-2had an average value of81,104and142μg/g, respectively, showing certain difference as compared to the normal deposited coals. The tectonic setting influenced largely the coals REE concentration in the upper coal-bearing sequences, and the geochemistry parameters of REE have significant correlations with the thickness of coal seams. |
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