中文摘要：

鲁溪黑云母花岗岩体和下庄二云母花岗岩体为粤北贵东复式岩体的重要组成部分。两岩体形成于相同构造背景，空间上紧密共生，时间上近乎同时生成，但鲁溪黑云母花岗岩不成矿，下庄二云母花岗岩赋存着大量铀矿床。对鲁溪黑云母岩体和下庄二云母进行系统的岩石学、矿物学、主量元素和微量元素分析，其结果表明，鲁溪黑云母花岗岩和下庄二云母花岗岩具有相似的地球化学特征，为同一母岩浆先后结晶分异的产物。岩浆不同演化阶段温度、氧逸度等物理化学条件的变化造成两岩体的铀含量和铀的赋存状态差异，致使鲁溪黑云母花岗岩的铀含量低，且铀主要以惰性铀存在，不利于成矿，而下庄二云母花岗岩的铀含量高，铀多以活性铀的形式存在，利于后期热液成矿。因此鲁溪岩体不成矿，而下庄岩体赋存着大量的铀矿床。

英文摘要：

The Luxi biotite granite and Xiazhuang two-mica granite are important part of Guidong composite pluton in the northern Guangdong Province. They have the same tectonic setting, close spatial association and close age. However, there are many uranium deposits in Xiazhuang two-mica granite while none in Luxi biotite granite. Based on studies of petrology,mineralogy, characteristics of major and trace elements, it is indicated that the Luxi biotite granite and Xiazhuang two-mica granite have the similar geochemical characteristics and they are at different evolutionary stage of the same parent. Different physical and chemical conditions such as temperature and oxygen fugacity of different evolutionary stage produce different uranium content. The Luxi biotite granite is of low uranium content occurred as the form of inert uranium, while Xiazhuang two-mica granite is of high uranium content occurred as th＇e form of mobile uranium. Therefore,there are many uranium deposits in Xiazhuang two-mica granite while none in Luxi biotite granite.