摘要
在前人研究基础上,利用激光剥蚀电感耦合等离子质谱(LA-ICP-MS)锆石U-Pb定年方法,通过进一步改进测试流程、优化仪器参数及增加氮气等辅助气体增敏设备,最大程度提升小束斑LA-ICP-MS中的灵敏度并降低元素分馏效应。对此,本文对Qinghu、Ple2ovice、Tanz 3个标准锆石在束斑直径分别为32μm、24μm和16μm条件下进行了定年研究。实验结果显示:在32μm小束斑条件下,标准锆石Qinghu的^(206)Pb/^(238)U的年龄范围为162~157 Ma,^(206)Pb/^(238)U加权平均年龄为159.5±0.8 Ma(2σ,n=26,MSWD=0.36);标准锆石Ple2ovice的^(206)Pb/^(238)U的年龄范围为340~334 Ma,^(206)Pb/^(238)U加权平均年龄为337.1±1.5 Ma(2σ,n=27,MSWD=0.085);标准锆石Tanz的^(206)Pb/^(238)U的年龄范围为574~562 Ma,^(206)Pb/^(238)U加权平均年龄为566.6±2.9 Ma(2σ,n=29,MSWD=0.070)。在24μm小束斑条件下,标准锆石Qinghu的^(206)Pb/^(238)U的年龄范围为162~157 Ma,^(206)Pb/^(238)U加权平均年龄为159.3±0.7 Ma(2σ,n=30,MSWD=0.22);标准锆石Ple2ovice的^(206)Pb/^(238)U年龄范围为341~334 Ma,^(206)Pb/^(238)U加权平均年龄为337.2±1.5 Ma(2σ,n=29,MSWD=0.13);标准锆石Tanz的^(206)Pb/^(238)U年龄范围为568~561 Ma,^(206)Pb/^(238)U加权平均年龄为566.5±2.9 Ma(2σ,n=30,MSWD=0.054)。在16μm小束斑条件下,标准锆石Qinghu的^(206)Pb/^(238)U年龄范围为163~154 Ma,^(206)Pb/^(238)U加权平均年龄为159.5±1.4 Ma(2σ,n=25,MSWD=0.45);标准锆石Ple2ovice的^(206)Pb/^(238)U年龄范围为340~334 Ma,^(206)Pb/^(238)U加权平均年龄为337.3±2.0 Ma(2σ,n=30,MSWD=0.063);标准锆石Tanz的^(206)Pb/^(238)U年龄范围为575~563 Ma,^(206)Pb/^(238)U加权平均年龄为567.0±4.3 Ma(2σ,n=30,MSWD=0.028)。以上结果表明,Qinghu、Ple2ovice、Tanz 3个标准锆石加权平均年龄与推荐值在误差范围内完全吻合。因此,文中尝试建立的小束斑(24μm及16μm)锆石LA-ICP-MS U-Pb定年新方法具有可行性。该方法的建立有利于扩大LA-ICP-MS锆石U-Pb定年的应用范围,对颗粒较小、结构复杂的锆石颗粒进行定年分析,具有重要的理论研究意义与经济价值。
Building on previous research,we employed laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb dating method to maximize sensitivity and minimize elemental fractionation effects.This was achieved by improving the testing process,optimizing the instrument parameters,and incorporating auxiliary gas sensitization equipment,such as nitrogen.In this study,three standard zircons—Qinghu,Ple2ovice,and Tanz—were dated using beam spot diameters of 32,24,and 16μm,respectively.The experimental results reveal that with a 32μm beam spot,standard zircon Qinghu^(206)Pb/^(238)U age range is 162~157 Ma,weighted average^(206)Pb/^(238)U age is 159.5±0.8 Ma(2σ,n=6,MSWD=0.36);Standard zircon Ple2ovice^(206)Pb/^(238)U age range is 340~334 Ma,weighted average^(206)Pb/^(238)U age is 337.1±1.5 Ma(2σ,n=27,MSWD=0.085);Standard zircon Tanz^(206)Pb/^(238)U age range is between 574~562 Ma,weighted average^(206)Pb/^(238)U age 566.6±2.9 Ma(2σ,n=29,MSWD=0.070).With a 24μm beam spot,standard zircon Qinghu^(206)Pb/^(238)U age range is 162~157 Ma,weighted average^(206)Pb/^(238)U age is 159.3±0.7 Ma(2σ,n=30,MSWD=0.22);Standard zircon Ple2ovice^(206)Pb/^(238)U age range is 341~334 Ma,weighted average^(206)Pb/^(238)U age is 337.2±1.5 Ma(2σ,n=29,MSWD=0.13);Standard zircon Tanz^(206)Pb/^(238)U age range is 568~561 Ma,weighted average^(206)Pb/^(238)U age is 566.5±2.9 Ma(2σ,n=30,MSWD=0.054).With a 16μm beam spot,standard zircon Qinghu^(206)Pb/^(238)U age range is 163~154 Ma,weighted average^(206)Pb/^(238)U age is 159.5±1.4 Ma(2σ,n=25,MSWD=0.45);Standard zircon Ple2ovice^(206)Pb/^(238)U age range is 340~334 Ma,weighted average^(206)Pb/^(238)U age is 337.3±2.0 Ma(2σ,n=30,MSWD=0.063);Standard zircon Tanz^(206)Pb/^(238)U age range is 575~563 Ma,weighted average^(206)Pb/^(238)U age is 567.0±4.3 Ma(2σ,n=30,MSWD=0.028).The weighted average ages of the three standard zircons(Qinghu,Ple2ovice,and Tanz)are consistent with their recommended values within the margin of error.These findings demonstrate the feasibility of using small beam spot sizes(24μm and 16μm)for zircon LA-ICP-MS U-Pb dating.This refined method extends the applicability of LA-ICP-MS zircon U-Pb dating,making it suitable for small zircon grains with complex structures.This model has significant theoretical research implications and economic value.
作者
孟重天
郝宇杰
李予晋
王世昌
任枫荻
张宇婷
商青青
张峻硕
李泽宇
罗炜丞
MENG Chong-tian;HAO Yu-jie;LI Yu-jin;WANG Shi-chang;REN Feng-di;ZHANG Yu-ting;SHANG Qing-qing;ZHANG Jun-shuo;LI Ze-yu;LUO Wei-cheng(College of Earth Science,Jilin University,Changchun 130061,China;Key Laboratory of Mineral Resources Evaluation in Northest Asia,Ministry of Natural Resources,Changchun 130026,China)
出处
《岩石矿物学杂志》
北大核心
2025年第2期473-489,共17页
Acta Petrologica et Mineralogica
基金
吉林大学本科生创新创业训练计划(202310183225)
国家自然科学基金项目(41802078)。
