摘要
向阳坪矿床作为苗儿山矿田近年来新发现的花岗岩型铀矿床,发育大量原生沥青铀矿脉。为了进一步厘清铀矿床铀成矿年龄体系,采用LA-ICP-MS测试技术,对钻孔中揭露的脉状沥青铀矿开展了微区原位U-Pb同位素定年及稀土元素特征研究。LA-ICP-MS分析结果显示,向阳坪地区存在2期铀矿化,U-Pb年龄为51.59 Ma和41.10 Ma,前者为向阳坪矿床主成矿年龄,后者为后期流体活动导致沥青铀矿蚀变的热事件时间,分别与沙子江矿床主成矿期65~50 Ma、45~40 Ma相吻合。沥青铀矿稀土元素特征表明,稀土元素总量相对较高,具有明显的负Eu异常,其配分模式呈海鸥型,与低-高品位铀矿石的稀土元素配分模式相似,而与新鲜花岗岩、蚀变花岗碎裂岩的“右倾型”相区别。沥青铀矿稀土元素与铀元素的迁移具有同步性,为低温下晶出沉淀的产物。
The Xiangyangping uranium deposit is a newly discovered granite-type uranium deposit,which is one of the representative granite-hosted uranium deposits in the Miaoershan uranium ore field.The Xiangyangping uranium deposit has developed a large number of primary pitchblende veins,but the chronology characteristics of uranium minerals are obscure,especially the application of in-situ analysis technique is lacking.In order to further clarify the uranium mineralization age of the uranium deposits,in-situ U-Pb isotopic dating of pitchblende veins exposed in the borehole was studied by using LA-ICP-MS.The U-Pb age dating of the pitchblende obtained ages of 51.59 Ma and 41.10 Ma,suggesting that there are two phases of uranium mineralization in the Xiangyangping area,which are consistent with the main mineralization periods of 65-50 Ma and 45-40 Ma for the Shazijiang uranium deposit.The former is the main metallogenic age of Xiangyangping uranium ore deposit,while the latter is the thermal event time of late fluid activity leading to pitchblende alteration,indicating that there is a major uranium metallogenic event of about 52 Ma in the Miaoershan uranium ore field.The chondrite-normalized patterns of rare earth elements are rich in light-REE,with obvious negative Eu anomalies.The distribution curve of rare earth elements in pitchblende is characterized by in seagull pattern,which is similar to low-high grade uranium ore,and different from the"right-dipping type"of fresh granite and altered granitic cataclastic rock.The migration of REE and pitchblende was synchronous,which is the product of crystallization and precipitation at a low-temperature hydrothermal environment.
作者
李杰
黄宏业
刘子杰
张涛
陈琪
邹明亮
Li Jie;Huang Hongye;Liu Zijie;Zhang Tao;Cheng Qi;Zou Mingliang(Research Institute No.230,CNNC,Changsha 410007,China)
出处
《地质科技通报》
CAS
CSCD
北大核心
2021年第1期90-99,共10页
Bulletin of Geological Science and Technology
基金
国家自然科学基金项目(41702102)
中国核工业集团有限公司项目(3210402)。
作者简介
李杰(1991-),男,工程师,主要从事铀矿地质勘查与科研工作。E-mail:lijie568521@qq.com;通信作者:邹明亮(1983-),男,高级工程师,主要从事铀成矿作用研究。E-mail:zoumingliang2001@163.com。
