Geochemical signatures of the trace elements in the Neogene lignites in the Husa Basin,western Yunnan

In order to investigate geochemical signatures of the trace elements in the Neogene lignites in the Husa Basin, western Yunnan, a total of 15 layers of fresh lignite samples were collected in 5 boreholes, and the trace elements were determined by using ICP-MS. The Neogene lignites in the Husa Basin display significant enrichment of the elements Rb, Cs, Th, and slight enrichment of the elements Be, Sc, Cr, Cu, Ga, In, W, Pb and U when compared to the common Chinese coals. The potentially hazardous trace elements in the lignites in the Husa Basin include the elements Be (5.32mg/kg), Cr (39.8 mg/kg), Cu (39.7 mg/kg), Pb (32.8 mg/kg), Th (39.3 mg/kg) and U (7.39 mg/kg). The REE concentrations in the lignites in the Husa Basin range from 196.03 to 550.42mg/kg, with an average of 306.71 mg/kg, much higher than that of the common Chinese coals. The right-leaning REE distribution patterns suggest the significant LREE enrichment and relative HREE depletion, and are in general agreement with those of the upper crust. The negative Ce anomaly and trace elelment ratios indicate that the peats in the Husa Basin were once deposited in the acidic reducing sedimentary environments. The negative Eu anomaly and chondrite-normalized REE distribution patterns indicate that the origins of the Neogene lignites in the Husa Basin have something to do with the terrigenous supply of acidic granites along the margins of the Husa Basin.