粤北产铀与不产铀花岗岩中铀矿物特征的电子探针研究及其找矿意义

晶质铀矿的含量、形貌、成分、铀矿物类型、与铀矿物共存的矿物组合等特征可以作为产铀与不产铀岩体的判别标志,为花岗岩型铀矿找矿工作提供了一种新的技术手段。长江岩体和九峰岩体是粤北地区典型的产铀与不产铀花岗岩体,本文利用电子探针测试了九峰岩体的铀矿物并与长江岩体进行对比研究。结果表明九峰岩体的铀矿物主要为晶质铀矿,其化学年龄可分为两组,分别为~160 Ma、~105 Ma,与长江岩体的两组晶质铀矿年龄基本一致;其中第一组年龄代表岩体的成岩年龄,第二组年龄与粤北地区~105 Ma的基性岩脉侵入时代相对应;但九峰岩体缺少长江岩体中~74 Ma的成矿年龄。相比于长江岩体,九峰岩体的铀矿物受到后期热液事件的影响较小,U没有发生明显的活化、转移,因而未能富集成矿,没有形成具有工业价值的铀矿床。

EPMA Study on Characteristics of Uranium Minerals in Uranium-bearing and Uranium-barren Granites in Northern Guangdong and Its Prospecting Significance

The content, morphology and composition of uraninite, uranium minerals types, mineral assemblages coexisting with uranium minerals can be used as the distinguishing marks of uranium-bearing and non-uranium-bearing granites, which provide a new technique for the prospecting work of granite-hosted deposits. Changjiang granite and Jiufeng granite are typical uranium-bearing and non-uranium-bearing granites in northern Guangdong. Uranium minerals of Jiufeng granite are studied by Electron Microprobe and compared with Changjiang granite. Results show that the main types of uranium minerals of Jiufeng granite is uraninite, and its ages dated by Electron Microprobe can be divided to two groups, 160 Ma and 105 Ma, which are consistent with the two ages groups of uraninite in Changjiang granite. The first group represents the formation age, and the second group corresponds to 103 Ma mafic dikes'' invasion age. Compared with Changjiang granite, uranium minerals are less affected by the late hydrothermal events in Jiufeng granite, and furthermore obvious U activation and migration did not happened, so there exist no uranium mineralization in Jiufeng granite and no uranium deposits of industrial value.