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利用193nm LA-ICP-MS在20μm小斑束条件下对3个国际标准锆石样品和一个实验室内部的标准锆石样品进行了U-Pb年龄和20个微量元素的同时测定.测定结果显示,91500,GJ1和TEMORA1(TEM)三个国际标准锆石样品的206Pb/238U加权平均年龄分别为(1064.4±4.8)Ma(2σ,n=15),(603.2±2.4)Ma(2σ,n=15)和(418.2±2.4)Ma(2σ,n=11),其分析的单点相对偏差(2σ)均小于2.2%,加权平均年龄的相对偏差(2σ)均小于0.6%.这些年龄测定值与推荐值之间在误差范围内完全一致.一个实验室内部标准锆石样品SK10-2(来自辽东地区细粒辉长岩)的206Pb/228U加权平均年龄为(31.42±0.25)Ma(2σ,n=16),其单点相对偏差(2σ)为2.4%～5.7%,加权平均年龄的相对偏差(2σ)为0.80%,与Yuan等测定结果一致.利用相同的仪器测试条件对NIST612和NIST614中微量元素进行了测定,测定值与推荐值在误差范围内完全一致.在年龄测定的同时,采用NIST610作外标,对微量元素分布不均匀的91500和GJ1锆石中的微量元素进行了分析,91500的测定值基本落在文献提供的元素含量变化范围之内,GJ1锆石中Pb,Th和U含量的测定值也落在TIMS测定值之内.4个锆石样品平滑性的稀土元素球粒陨石标准化曲线表明,所获得的稀土元素之间的相对含量也是准确的.这些分析表明,本次研究所建立的LA-ICP-MS分析方法,在20μm激光斑束条件下,不仅可准确测定锆石的U-Pb年龄,而且可以同时较准确的获得锆石的微量元素组成.
The simultaneous determination of U-Pb age and 20 trace elements in three international standard zircon samples and one standard zircon sample in the laboratory was carried out using a 193 nm LA-ICP-MS at 20 μm spotlight. (1064.4 ± 4.8) Ma (2σ, n = 15), (603.2 ± 2.4) Ma (2σ, n = 15) were obtained for the three international standard zircon samples of 91500, GJ1 and TEMORA1 15) and (418.2 ± 2.4) Ma (2σ, n = 11), the relative single point deviation (2σ) was less than 2.2% and the relative mean deviation (2σ) of weighted average age was less than 0.6% (31.42 ± 0.25) Ma (2σ, 2σ) of 206Pb / 228U for the standard zircon sample SK10-2 (from Liaodong area, fine-grained gabbro) n = 16), the relative deviation (2σ) of single point was 2.4% ~ 5.7%, and the relative deviation (2σ) of weighted average age was 0.80%, which was consistent with the results of Yuan et al.Using the same instrumental test conditions, NIST612 and NIST614 Trace elements were measured, the measured value and the recommended value within the error range exactly the same age determination, the use of NIST610 as external standard, the trace elements Uneven trace elements in 91500 and GJ1 zircons were analyzed. The measured values of 91500 fall within the range of elemental contents provided in the literature. The values of Pb, Th and U in GJ1 zircon also fall within the range of TIMS The results show that the relative content of rare earth elements obtained is also accurate.These analyzes indicate that the LA-ICP- MS method can not only accurately determine the zircon U-Pb age under 20μm laser spot, but also obtain the trace element composition of zircon more accurately.