REE geochemistry of clay in coal measures of Shanxi Formation in the north of North China

The contents of REE in 11 samples of the clay rocks from the coal measures of the Shanxi Formation of Permian of several regions of the north of North China are detected by ICP-AES and INAA.The results show that the REE contents of the samples changes very greatly, the ΣREE from 49.43 mg/kg to 478.66 mg/kg, 165.04 mg/kg in average, slightly lower than that of NASC, and the ratios ΣLREE/ΣHREE is 3.44~21.23, 9.74 in average, close to 7.68 of NASC.Most samples have moderate to severe losses in Eu and weak to moderate negative anomalies in Ce.The samples, on the REE, are not of the typical characteristics of sedimentogenic mudstone, and, combining with the results of the rock and mineral analyses and the early study, the clay rocks may be composed of in-situ alterated neutral, basic or acidic(alkaline) volcanic debris and to varying degrees mixed with terrigenous sediments.