粤赣花岗岩型铀矿床矿石中沥青铀矿化学成分特征及成因分析

Chemical Composition and Genetic Analysis of Pitchblende from the Uranium Deposit of Granite Type in Guangdong and Jiangxi Province

根据粤北诸广矿区水石、塘湾矿床和江西桃山矿区牛尾岭和大府上矿床采集的铀矿石样品进行了岩矿鉴定,并用电子探针测定了114个测点的沥青铀矿的化学成分,研究认为,该区沥青铀矿化学成分都表现出除UO_2外,SiO_2,CaO含量高,UO_2含量与SiO_2,P_2O_5呈负相关,与CaO,PbO,FeO,MnO等弱正相关等特点,对其成因作如下分析:在沥青铀矿形成过程中,铀硅存在互消长关系,根据铀硅等可以呈独立铀矿物、类质同象、吸附等形式存在的原理,Si^(4+)还可能以内潜同晶等形式出现;Ca^(2+)与U^(4+)离子半径相近,能以类质同象形式参加至沥青铀矿的晶体结构中;铅除呈包裹体矿物的方铅矿所含有的Pb以外,还有铀的放射性蜕变的产物;铀与铁、锰、磷关系密切,它们极有可能以包裹体微粒、离子状态进入沥青铀矿中。

The uranium ore samples are carried out rock-mineral determination that collected from the Shuishi, Tangwan deposits in Zhuguang Diggings the north of Guangdong and the Niuweiling, Dafushang deposits in Taos- han Diggings of Jiangxi province. Meanwhile, the chemical component of pitchblende are researched from 114 a- nalysis-points that carried out by electronic probe. The results revealed that the pitchblende has the characteristics of high SiO2 and CaO, the UO2 showed negative correlation between Al2O3 and P2 05, whereas FeO, PbO, MnO, CaO exhibit a weak-positive correlation with UO2. Based on these new data, this article suggest that a reciprocal relationship between U and Si are last in the formation process of pitchblende. According to the theory that U and Si could exist in the independent uranium minerals, isomorphism and adsorption, we consider the Si^4＋ may occur in the form of incomplete isomorphism. And the Ca^2＋ have the similar ionic radius with the U^4＋ , which it could take part in the crystal structure of pitchblende. Pb are mainly from the gelenite mineral inclusions, and parts from the the products of the radioactive decay of U. U have the closely association with the Fe, Mn, P, and these elements are highly possible enter into the pitchblende in the form of inclusion particles or the ionic condition.