由于花岗岩型铀矿床中沥青铀矿在组成和结构上的固有特点，难以用挑选沥青铀矿样品溶样的传统定年方法精确确定其形成年龄。近年发展的沥青铀矿SIMS原位微区U-Pb定年方法，为精确测定其形成年龄创造了条件。华南是我国最重要的铀矿产区之一，花岗岩型铀矿床在其中占有至关重要地位。虽然这些花岗岩型铀矿床其他方面的研究已取得重要进展，但其成矿时代一直还未能得到很好的厘定，这严重制约了对华南花岗岩型铀矿床成矿作用与相应地质事件之间关系的正确认识。本项目选择华南规模最大的花岗岩型铀矿床（302花岗岩型铀矿床）为研究对象，在详细的沥青铀矿矿物学和矿物生成顺序研究的基础上，开展系统的沥青铀矿SIMS原位微区U-Pb年代学研究，以精确厘定302铀矿床的成矿时代。这项研究不仅对深入认识302花岗岩型铀矿床本身的形成机制具有重要意义，而且也是建立国内SIMS U-Pb定年方法及发展华南花岗岩型铀矿床成矿理论的重要基础。

Granite-hosted uranium deposit is one of the most important types of uranium deposit in South China. The southeastern part of the Nanling metallogenic province, China is host to numerous granite-hosted vein-type hydrothermal uranium deposits. The geology and geochemistry of these deposits have been extensively studied. However, the accurate and precise ages for uranium mineralization of granite-hosted uranium deposits are scarce because the uranium minerals in these deposits are usually fine grained, and may have formed in several stages. Therefore, the ages previously obtained by the bulk dating techniques are possibly a mixed age which severely restrict the correct understanding the relationship between uranium mineralization and corresponding geological events for these uranium deposits in South China. Recently, an ideally method for in-situ U-Pb isotopic analyses by SIMS has been developed for uranium minerals with a range of chemical compositions, and fine-grained uranium oxides associated with uranium deposits. This project will focus on the uraninite SIMS U-Pb geochronology of the largest No. 302 granite-hosted uranium deposit in the northern Guangdong province, China. Based on the detailed minerology, mineral arisen sequence and previous studies, SIMS U-Pb dating technique will obtain the precious ore-forming age of the No. 302 uranium deposit. This study will not only reveal the genesis of the No. 302 granite-hosted uranium deposit, but establish the method of in-situ uraninite SIMS U-Pb dating and develop the important metallogenic theory for the granite-hosted uranium deposit in South China.