Study On Uranium Minerals Of Zhuguangshan Complex Pluton,Northern Guangdong

Zhuguangshan area is an important gathering place of granite-type uranium deposits in northern Guangdong. The geochemistry, geochronology and the genesis of uranium deposits in this region have been extensively studied. However, the uranium minerals of Zhuguangshan complex pluton have not yet been systematically studied. In this paper, uranium minerals of Indosinian and Yanshanian granites are studied by electron microprobe to discuss the diagenesis and mineralization of uranium deposits in Zhuguangshan area. Results show that:Yanshanian Uranium-bearing and barren granites(such as Changjiang and Jiufeng granites) show great differences in the content, morphology and composition of uraninite, uranium minerals types, mineral assemblages coexisting with uranium minerals. Compared with barren granite, uranium minerals of uranium-bearing granite have higher content, often associated with reducing minerals(such as pyrite), composition changes larger, and the main types of uranium minerals are uraninite, pitchblende, coffinite and so on. Uraninite records the rock formation age(~160Ma) of uranium-bearing and barren granites, and a hydrothermal activity age ~105Ma. However, pitchblende in uranium-bearing granite also records the metallogenic age ~70Ma, indicating uranium-bearing granite has experienced more late hydrothermal actions before it leads to mineralization. The above differences 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.Uanium minerals of the No. 302 uramium deposit which has obvious alteration zoning phenomenon in the Changjiang uranium mining area are studied systemically by electron microprobe. Using electron microprobe dating method on uraninite and pitchblende in different alteration zones. Results show that the chemical age of uraninite 165±2.5Ma represents the rock formation age of Changjiang granite. The chemical ages of pitchblende can be divided into four groups: ~120Ma, ~105Ma, ~92Ma, ~70Ma, all of which represent the multiple stages of hydrothermal activity times in the mining area, and also represent multiple stages of uranium mineralization ages in northern Guangdong. The first three groups represent the early stages of uranium mineralization, and the forth group represent the main metallogenic epoch.Uraninite in the two Indosinian uranium granites(Youdong and Longhuashan granites) also dated by electron microprobe. The chemical ages of Youdong granite can be divided into two ages, ~228Ma, ~160Ma, the first group represents the rock formation age of Youdong granite, and the second group corresponds to the rock formation age of the intrusive Changjiang granite. There exist no late intrusive granites around Longhuashan granite, so the chemical ages of uraninite has only one group, ~230Ma, which represents the rock formation age of Longhuashan granite. The above results show uraninite in the granites not only can record its own rock formation ages, also can record the ages of the late intrusive granites.