锆石铀-铅定年激光剥蚀-电感耦合等离子体质谱原位微区分析进展

激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)技术是目前最常用的锆石U-Pb同位素年龄测定方法之一。该方法能够对单颗粒锆石内部年龄差异实现快速、准确的原位微区分析。文章总结了近年来激光剥蚀系统、ICP-MS技术以及LA-ICP-MS锆石U-Pb定年方法、相关应用实例研究的进展和现状。系统评述了激光发生器,剥蚀池,剥蚀参数(激光波长、脉冲宽度、剥蚀气体、孔径大小)以及四极杆和扇形磁场质谱仪对锆石U-Pb年龄数据的精度和准确度的影响。详细介绍了基于锆石年龄标准样品、标准溶液及其他标样的外标定量校准方法,单个U/Pb比值计算方法,普通铅校正方法以及同位素年龄与微量元素同时测定的方法。目前LA-ICP-MS锆石U-Pb定年技术主要应用于碎屑锆石的沉积物源区示踪和岩浆事件的年代学约束研究。

Advances in in situ Microanalysis of U-Pb Zircon Geochronology Using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) analysis is one of the most popular methods for isotope geochronology of zircon. This technique was applied to accurately and rapidly demonstrate the age heterogeneities within a single zircon crystal. In this review the main stages of the evolution of this in situ microanalysis technique, including laser ablation system, ICP-MS, U-Pb dating methodology of zircon and applications are summarized. The influences from the laser device, ablation cell, laser ablation parameters (laser wavelength, laser pulse duration, ambient gas and crater size), quadrupole and magnetic sector ICP-MS on the precision and accuracy of U-Pb dating data are discussed. The quantitative calibration with natural zircon age standards and other standards, single U/Pb ratios calculation, correction for common Pb and simultaneous determinations of U-Pb age and trace element compositions are also introduced in this paper. At present, there are numerous zircon U-Pb geochronlogical applications for tracing sedimentary provenance studies and dating magmatic events by LA-ICP-MS.