| LA-ICP-MS锆石微区U-Pb定年方法及不同束斑直径对年龄结果的影响作用探讨 |
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| 引用本文： | 王森,张拴宏,张琪琪,梁霞,孔令昊,胡国辉,王开,王宏宇,蔡瑜杭.LA-ICP-MS锆石微区U-Pb定年方法及不同束斑直径对年龄结果的影响作用探讨[J].地质力学学报,2022,28(4):642-652. |
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| 作者姓名： | 王森 张拴宏 张琪琪 梁霞 孔令昊 胡国辉 王开 王宏宇 蔡瑜杭 |
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| 作者单位： | 1.中国地质科学院地质力学研究所, 北京 100081 |
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| 基金项目： | 国家重点研发计划项目2018YFC0603802中国地质科学院地质力学研究所中央财政科研项目结余经费新开项目No.54 |
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| 摘 要： | 利用自然资源部古地磁与古构造重建重点实验室新引进的GeoLas HD型193nm ArF准分子激光剥蚀系统和Agilent 7900型四极杆电感耦合等离子质谱仪，成功建立了LA-ICP-MS锆石微区U-Pb定年及微量元素分析测试方法。以标准锆石91500为外标，在32 μm束斑直径、5.0 J/cm2能量密度和5 Hz剥蚀频率等实验条件下，对Ple?ovice、Temora1和Qinghu锆石标样开展了U-Pb定年实验，所测年龄结果与各标样推荐值在误差范围允许的条件下一致，并且Ple?ovice年龄结果在不同时间段内保持稳定。同时对未知年龄样品11-5开展了不同实验室测年结果对比研究，所测结果与中国地质大学(武汉)地质过程与矿产资源国家重点实验室所测年龄在误差允许范围内一致。以NIST SRM 610为外标，29Si为内标，分析测试了锆石91500和NIST SRM 612标准样品的微量元素含量，实验测试结果与推荐值一致。在此基础上探索总结了不同剥蚀斑束直径对U-Pb年龄结果的影响，认为在同样的能量密度和剥蚀频率条件下，16~44 μm的剥蚀直径可以获取可靠的锆石U-Pb年龄，但32~44 μm相比16~24 μm小斑束直径所测得的年龄更加精准。
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| 关 键 词： | LA-ICP-MS 锆石 U-Pb定年 微量元素 |
| 收稿时间： | 2021-10-14 |
In-situ zircon U-Pb dating method by LA-ICP-MS and discussions on the effect of different beam spot diameters on the dating results |
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| Institution: | 1.Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China2.Key Laboratory of Paleomagnetism and Tectonic Reconstruction, Ministry of Natural Resources, Beijing 100081, China3.Research Center of Polar Geosciences, China Geological Survey, Beijing 100081, China |
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| Abstract: | By using the newly introduced GeoLas HD 193 nm ArF excimer laser ablation system and the Agilent 7900 quadrupole inductively coupled plasma mass spectrometer (ICP-MS) in the Key Laboratory of Paleomagnetism and Tectonic Reconstruction at the Institute of Geomechanics, we successfully established the in-situ zircon U-Pb dating method and trace element analytical method by LA-ICP-MS. U-Pb dating experiments were carried out on Ple?ovice, Temora1 and Qinghu zircons under the experimental conditions of 32 μm beam spot diameter, 5.0 J/cm2 energy density and 5 Hz denudation frequency using the standard zircon 91500 as the external standard. The ideal age results are consistent with their recommended values, and the measured U-Pb ages for Ple?ovice zircon remain stable in different periods. Meanwhile, a comparative study of the U-Pb dating results in different laboratories was carried out on an unknown sample 11-5, and the dating results are consistent with that obtained in the State Key Laboratory of Geological Processes and Mineral Resources at China University of Geosciences (Wuhan) within analytical error. Trace elements in zircon standard 91500 and glass standard NIST SRM 612 were analyzed by using NIST SRM 610 as an external standard and 29Si as an internal standard, and the measured values are consistent with the recommended values of trace element contents. In addition, the influence of different beam spot diameters on the zircon U-Pb age results was explored by using the Ple?ovice zircon as an example. The results show that a denudation diameter of 16~44 μm can obtain reliable zircon U-Pb ages similar to the recommended age, and under the same energy density and denudation frequency conditions, U-Pb ages obtained by using 32~44 μm beam spot diameters are more accurate than those obtained by 16~24 μm beam spot diameters. |
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