电感耦合等离子体质谱仪与激光器联用测量条件优化及其在锆石U-Pb定年中的应用

摘要

During LA-ICP-MS analysis,the key factor influencing data accuracy of sample analysis is whether the sample can be uniformly delivered from the laser sample chamber to the torch of the ICP-MS. An external container between LA and ICP-MS and a multi-channel rotary sampling cell,which can effectively eliminate the sample position effect during the laser ablation was designed for the study reported in this paper. The pattern of aerosol delivered to ICP-MS is approximately continuous and at the same time,this can greatly improve the stability. Under optimal conditions,using 91500 as external standard,the standard zircons GJ-1,Ple ovice,TEMROA and QH yield U-Pb ages of 604 ± 3 Ma(2δ,MSWD = 1. 2),337 ± 1 Ma(2δ,MSWD = 1. 18),419 ± 3 Ma(2δ,MSWD= 0. 15)and 161 ± 1 Ma(2δ,MSWD = 0. 6),respectively,which agree well with the previously reported ID-TIMS and SHRIMP ages. For the same conditions,using NIST610 as external standard,most trace element results of the glass standards NIST612 and BHVO-2G fall within 10% range of the reference values. The 207 Pb / 206 Pb weighted mean age of zircons from the Tianshan Orogen of Xinjiang is consistent with the previous SHRIMP U-Pb age within uncertainty. This method can effectively reduce the elemental fractionation effects and improve the reliability of the analytical data.%在 LA - ICP - MS 测量中,样品是否能够均匀地由激光样品池运送到等离子体质谱仪炬管是影响分析数据精度的关键.本研究对样品剥蚀池和剥蚀气溶胶传输进行改进,在 LA 和 ICP - MS 之间添加一套激光剥蚀脉冲平滑系统将 LA 剥蚀气溶胶转化为连续送样模式,并使用多通道旋转式样品池消除样品在激光剥蚀池中的位置效应,显著提高了测量信号的稳定性.在优化条件下,以标准锆石 91500 作外标,测量锆石标样 GJ - 1、Ple?ovice、TEMORA、QH 的 U - Pb 年龄分别为 604 ± 3 Ma(2δ,MSWD = 1. 2)、337 ± 1 Ma(2δ,MSWD= 1. 18)、419 ± 3 Ma(2δ,MSWD = 0. 15)和 161 ± 1 Ma(2δ,MSWD = 0. 6),与前人报道结果在误差范围内一致;以 NIST610 作外标,玻璃标样 NIST612 和 BHVO - 2G 大部分微量稀土元素的测量值与参考值的相对偏差均在 10% 以内;测量新疆天山造山带锆石样品的207 Pb / 206 Pb加权年龄与 SHRIMP 结果基本吻合.本方法可有效降低元素分馏效应,提高测量精度.