粤北下庄335矿床成矿时代的厘定——来自LA-ICP-MS沥青铀矿U-Pb年龄的制约

Timing of No.335 ore deposit in Xiazhuang uranium orefield,northern Guangdong Province: Evidence from LA-ICP-MS U-Pb dating of pitchblende

文章采用LA-ICP-MS测试技术对下庄矿田335矿床的沥青铀矿开展了U-Pb微区定年工作。335矿床沥青铀矿的成分特征及微观形貌特征显示,本区沥青铀矿在初始形成之后受到过后期的一些地质事件的影响。本次获得沥青铀矿的最大年龄为(93.5±1.2)Ma。结合华南岩石圈伸展发生的时间、辉绿岩脉对铀矿的控制作用及矿区内辉绿岩脉的侵位时间,对本区铀矿的形成特点进行了探讨。结果表明,该年龄符合华南铀矿在时间上的一些客观成矿规律,可基本上代表335矿床的成矿年龄。

In this paper,an accurate U-Pb age of pitchblende was obtained from the No.335 uranium deposit in the Xiazhuang uranium orefield by using the LA-ICPMS technique.The compositional and micro-morphologic characteristics of the pitchblende from the No.335 ore deposit show that it has been altered by some subsequent geological events.（93.5±1.2） Ma is the oldest age in this study.A discussion has been made on the basis of integration of lithosphere extension timing of South China,the control of the diabase dike over the uranium mineralization and the emplacement time of diabase dikes in this ore deposit.It is revealed that the obtained age can reflect some rules of uranium ore formation in South China and might approximately represent the ore-forming age of the No.335 ore deposit.