下庄铀矿田337矿床成矿流体稀土元素示踪

337铀矿床位于下庄矿田东缘,区内发育近EW向、NNE向构造裂隙群及NW向辉绿岩和正长岩脉体,发育以碱性为主的多种围岩蚀变。区内矿床主要赋矿围岩的稀土元素特征属壳源型。矿石内金属矿物以沥青铀矿为主,矿石的LREE/HREE比值为3.25,Sm/Nd比值平均为0.307,Ce/Yb比值为7.127,这些数据都显示出成矿流体具有较深来源。矿石较围岩亏损稀土元素尤其是轻稀土元素,稀土元素分布模式平缓,与幔源辉绿岩特别是与正长岩的稀土元素分布模式相近,负铕异常比围岩更为强烈,反映成矿流体的来源具有幔源性。结合区域地质特征,可以认为337矿床成矿流体来源具有幔源性质。

REE Tracing on Ore-forming Fluid of 337 Uranium Ore Deposit in Xiazhuang orefield

337 uranium ore deposit lies to the east of the Xiazhuang orefield,and there are structural fracture groups with EW,NNE-trending,diabase and syenite vein with NW-trending in the deposit region.The metal material mainly is pitchblende,various kinds of wall-rock alterations are developed in the region,especially alkali alterations.The characteristics of REE indicates that it belongs to shell source type,and the ratio of LREE to HREE is 3.25,Sm to Nd is 0.307 on average,and Ce to Yb is 7.127,which all prove the ore-forming fluid has deeper source.The ores deficits more REE,especially LREE than wall-rocks,and partition curve is flat,which is approximately nearby to that of the mantle-source diabase,especially syenite.But the negative uranium abnormality is more obvious than wall-rock,showing that the source of ore-forming fluid is mantle-source type.All above the characteristics illustrates that 337 ore deposit ore-forming fluid has the characteristics of mantle source.