钍铀比值在判别铀成矿环境中的应用研究——以粤北书楼丘铀矿床为例

Application of the Thorium-Uranium Ratio in Identifying Uranium Metallogenic Environment:An Example of the Shulouqiu Uranium Deposit in Northern Guangdong Province

钍铀比值是反映铀成矿信息的重要参数,地面伽玛能谱钍铀比值(Th/U)、分量钍铀比值(FTh/U)可分别指示花岗岩地区构造蚀变带型铀矿浅部及深部的矿化信息,从多角度、多尺度呈现铀富集环境。本文重点探讨利用Th/U、FTh/U分别提取浅部和深部铀成矿信息的可能性,并在粤北书楼丘铀矿床已知勘探剖面进行方法有效性试验。试验结果表明:Th/U、FTh/U能分别指示浅表和深部铀成矿环境;Th/U、FTh/U与浅表、深部铀富集程度呈负相关,且建立了钍铀比值与铀富集程度间的判别关系;FTh/U除与深部铀富集程度相关外,还与铀矿体中心埋深有关,FTh/U幅值越大,矿体埋深越深,并进一步建立FTh/U幅值与矿体中心埋深间的半定量关系式。综上,利用钍铀比值法在书楼丘外围开展铀成矿有利地段预测,并取得较好应用效果,成功预测4片浅部、5片深部铀成矿有利地段,其中FTh/U-2号深部异常已被钻探工程揭露证实。本次研究对书楼丘地区下一步找矿工作的部署与开展具有重要借鉴意义。

The ratio of thorium to uranium is an important parameter reflecting uranium mineralization information.This ratio in ground gamma spectroscopy(Th/U)and its fraction(FTh/U)from component geochemical survey can reveal shallow and deep mineralization information on tectonic-alteration zone type uranium deposits in granite areas,respectively,as well as the uranium enrichment environment from multi-angle and multi-scale.This article focuses on the possibility of extracting such information by using Th/U and FTh/U,and carries out a validity test of this method in an existing exploration profile of the Shulouqiu uranium deposit in northern Guangdong.The results show that Th/U and FTh/U can indicate superficial and deep uranium ore-forming environments,respectively.They are negatively correlated with the uranium enrichment degree of superficial and deep zones,permitting to establish a mathematic relationship between the thorium-uranium ratio and uranium enrichment degree.The value of FTh/U is related to not only the enrichment degree of uranium,but also the central burial depth of the uranium ore body.The deeper the buried depth of the ore body is,the greater the value of FTh/U is.And a semi-quantitative relationship between the value of FTh/U and the buried depth of the ore body center is further established.Using this method,four shallow and five deep favorable zones of uranium mineralization are successfully predicted in the perimeter of the Shulouqiu uranium deposit.Of them,the anomaly No.FTh/U-2 at depth is verified by later drilling.This study is of great significance for deployment and implementation of the next exploration in the Shulouqiu district.