华南诸广山中部鹿井铀矿田构造活化数值模拟

Numerical Simulation of Structural Reactivation of the Lujing Uranium Orefield in Central Zhuguangshan,South China

桃山‒诸广山成矿带作为华南重要的花岗岩型铀矿资源产区,构造活化对于带内热液铀矿的赋存空间起到了重要的控制作用。鹿井铀矿田位于桃山‒诸广成矿带中部,受NE向断裂的控制,矿体主要产于印支期花岗岩(牛尾岭、黄蜂岭、高昔以及羊角脑矿床)和寒武纪地层(鹿井铀矿床西部)内。前人研究表明鹿井铀矿田内存在多期次构造活化的形迹,但对于构造活化如何影响矿体赋存空间进而控制矿床空间分布缺乏细致的研究。本文利用FLAC3D数值模拟软件,探究了在不同构造应力背景下,断层活化形成的扩容区与已知矿床空间分布的关系。模拟结果表明,白垩纪‒新近纪的拉张构造运动能造成先存断裂的活化,进而产生扩容区,有利于成矿。因此在NW向伸展构造环境下,NE向先存断裂的活化是控制鹿井铀矿田内各矿床分布的重要条件。

The Taoshan-Zhuguangshan metallogenic belt is an important area of granite-type uranium mineralization in South China.Tectonic reactivation played an important role in controlling the distribution of the hydrothermal uranium deposits in the belt.The Lujing orefield is located in the center of the Taoshan-Zhuguangshan metallogenic belt and controlled by the NE-trending faults.The ore bodies are mainly hosted in the Indonesian granites(the Niuweiling,Huangfengling,Gaoxi,and Yangjiaonao deposits)and Cambrian metamorphic rocks(the Lujing uranium deposit in the west).Previous studies have shown evidence of multi-stage tectonic activation,however,there is a lack of detailed research on how tectonic activation affects the occurrence of ore bodies and spatial distribution of the deposits.FLAC3D is used in this paper to explore the relationship between dilation formed by fault reactivation and spatial distribution of the deposits under different tectonic backgrounds.The simulation results show that the extensional tectonic movement from Cretaceous to Neogene may reactivate the pre-existed faults,and produce dilatation zone,which is beneficial to mineralization.The results show that the reactivation of the NE-trending pre-existed faults,under NW-trending extensional tectonic environment,is the major factor controlling the distribution of the deposits in the Lujing uranium orefield.