LA-ICP-MS铀矿物微区原位U-Pb同位素年龄测定  

In-situ U-Pb Dating of Uraninite by LA-ICP-MS

作　　者：刘瑞萍[1] 郭冬发[1] 崔建勇[1] 武勇 何升[1] 李黎 谢胜凯[1] LIU Ruiping;GUO Dongfa;CUI Jianyong;WU Yong;HE Sheng;LI Li;XIE Shengkai(Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]核工业北京地质研究院,北京100029

出　　处：《铀矿地质》2021年第6期1141-1154,共14页Uranium Geology

基　　金：中国核工业地质局铀矿地质项目(编号:2021-22-7和201590);核能开发项目(编号:测HDJS2102);中核集团启明星项目(编号:QNYC2019-2)联合资助。

摘　　要：铀矿物作为铀矿床最重要的矿石矿物,对其进行准确的U-Pb年龄测定对厘定铀矿床成矿时代具有重要的意义。利用193 nm准分子激光器和高分辨电感耦合等离子体质谱仪(HR-ICP-MS),对沥青铀矿GBW004420 U-Pb年龄的均一性进行了检验,并对其作为铀矿物LA-ICP-MS微区原位U-Pb同位素定年标准物质的适用性进行了讨论。建立了铀矿物微区原位U-Pb同位素年龄测定方法,该方法适用于沥青铀矿和晶质铀矿U-Pb年龄的测定。对光石沟伟晶岩型铀矿床的晶质铀矿和牟定铀矿床的沥青铀矿进行了U-Pb同位素定年研究,获得的206Pb/238U加权平均年龄分别为(401.1±2.9)Ma和(950.2±9.8)Ma。研究结果表明沥青铀矿GBW04420的U-Pb年龄分布总体上是均匀的,可以作为铀矿物LA-ICP-MS微区原位U-Pb同位素定年的标准物质,使用过程中需要注意其中细脉的影响。Accurate U-Pb dating of uraninite,which is the most important ore mineral of uranium deposit,is of great significance to constrain the time of mineralization.We checked the homogeneity of U-Pb age of pitchblende GBW04420 using a Geolas 193 nm laser-ablation system together with a high resolution inductively coupled plasma mass spectrometry(HR-ICP-MS).The applicability that GBW04420 was used as standard material for in-situ U-Pb dating of uraninite by LA-ICP-MS was discussed.An in-situ U-Pb dating method for uraninite has been established.Two uranium minerals respectively from Guangshigou uranium deposit and Mouding uranium deposit have been determined by this method.The analyses yield weighted mean 206Pb/238U ages of(401.1±2.9)Ma and(950.2±9.8)Ma for these two samples,showing satisfactory results.The results prove that the U-Pb age of pitchblende GBW04420 is generally homogeneous and can be used as standard material for in-situ U-Pb dating of uraninite,but the effect of veins in pitchblende GBW04420 should be concerned during the application.

关 键 词：铀矿物 LA-ICP-MS U-PB同位素 GBW04420 

分 类 号：P597.1[天文地球—地球化学]