相山、下庄铀矿田稀土元素特征及示踪研究

相山、下庄两个铀矿田主要赋矿围岩的稀土元素特征极具相似性,显示出壳源型的特点。但它们的矿石稀土元素特征有很大的不同,相山铀矿田矿石稀土元素特别是重稀土元素含量与铀含量呈正相关,负铕异常和围岩相同。而下庄铀矿田矿石亏损稀土元素尤其是轻稀土元素,负铕异常比围岩更强烈,与幔源辉绿岩、正长岩的稀土元素分布模式相近。两矿田矿石稀土元素含量上存在明显差异的同时,都具有比其围岩LREE/HREE比值大幅度降低的特点。结合区域地质演化,认为两铀矿田矿石稀土元素具有不同的特征,但成矿流体都具有幔源性质,矿床都是在白垩—第三纪地壳拉张环境下形成的。

Research on the REE Characteristics and Tracing in Xiangshan and Xiazhuang Uranium Ore Fields

There are some great similarities in the REE characteristics of the mainly ore-bearing wall-rock between Xiangshan and Xiazhuang U-ore fields.But the REE features of ore differ greatly.In Xiangshan uranium ore field,the content of ERR,particularly HERR,have positive correlation with U and its abnormity of negative Eu is similar to that of wall-rock.While in Xiazhuang uranium ore field,the ore decrement REE,particularly LREE,exceed wall-rock in the abnormity of negative Eu,and its distribution pattern of REE is similar to that of mantle-resource diabase and syenite.The ore of two fields share the same characteristic that the ratio of LREE to HREE decrease in larger scale than that of wall rock,while the content of REE differs.All the characteristics above illustrate,combining their regionally geologic evolution,that although the REE characteristics differ in the two uranium ore fields,but the ore-forming fluid have the same characteristics of mantle source,the two ore fields were formed under the tensile surrounding of the crust in cretaceous-tertiary period.