华北北部山西组煤系粘土岩稀土元素地球化学特征

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

分别采用电感耦合等离子发射光谱(ICP-AES)和中子活化法(INAA)对采自河北兴隆、天津蓟玉、山西大同和阳泉、内蒙老窝铺以及宁夏石嘴山和石炭井二叠系山西组的11个粘土岩样品进行了稀土元素含量测定。结果表明:研究样品的稀土元素含量变化很大,∑REE最低49.43mg/kg,最高478.66mg/kg,平均165.04mg/kg,稍低于北美页岩(NASC)的173.21mg/kg;∑LREE/∑HREE介于3.44～21.23之间,平均9.74,与NASC的7.68相近;多为中—重度Eu亏损以及弱—中度Ce负异常。研究样品不具有典型的沉积型泥岩特征,结合薄片鉴定及前人分析结果推论,粘土岩可能分别由中、基性及酸性(偏碱)火山碎屑物质原地蚀变形成,并不同程度地混有陆源沉积物。

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∑REE 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∑LREE/∑HREE 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 al-terated neutral,basic or acidic（alkaline）volcanic debris and to varying degrees mixed with terrigenous sediments.