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, types of uranium minerals, and mineral assemblages coexisting with uranium minerals can be used as the distinguishing marks of uranium-bearing and uranium-barren granites, which provides a new technique for prospecting granite-hosted deposits. Changjiang and Jiufeng granitic intrusions are typical uranium-bearing and uranium-barren granites in northern Guangdong. Uranium minerals from these two granitic intrusions were studied by Electron Microprobe. Results show that the main uranium mineral of Jiufeng granite is uraninite, and its age dated by Electron Microprobe can be divided into two groups, 160 Ma and 105 Ma, which are consistent with those of uraninite in Changjiang granite. The first group age represents the formation age, and the second group corresponds to the invasion age of mafic dikes at 103 Ma. But the age of 74 Ma was not found for Jiufeng granite. Compared with Changjiang granite, uranium minerals of Jiufeng granite are less affected by the late hydrothermal events and U is not activated and migrated, so that no economic uranium deposits occur in Jiufeng granite.