Advances in U-Pb geochronology using a frequency quintupled Nd:YAG based laser ablation system (λ= 213 nm) and quadrupole based ICP-MS
Advances in U-Pb geochronology using a frequency quintupled Nd:YAG based laser ablation system (λ= 213 nm) and quadrupole based ICP-MS
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DOI：
10.1039/b300929g
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发表时间：
2003-07
影响因子：
3.4
通讯作者：
T. Jeffries;J. Fernández-Suárez;F. Corfu;G. G. Alonso-G.
中科院分区：
文献类型：
--
作者：
T. Jeffries;J. Fernández-Suárez;F. Corfu;G. G. Alonso-G.
研究了213 nm激光系统耦合四极ICP-MS对锆石U-Pb定年的分析潜力。研究对象为布列塔尼卡多米安带新元古代花岗岩类锆石。采用ID-TIMS对同一样品的7个锆石组分（含2个单粒）进行测年，得到参考年龄和误差，评价LA-ICP-MS U-Pb测定结果的准确性和精密度。用ID-TIMS对结晶年龄的最佳估计为603±2 Ma。LA-ICP-MS分析分两阶段进行，一阶段仅使用Ar作为载气，另一阶段使用Ar + He。在这两种情况下，年龄结果都在ID-TIMS年龄的分析不确定度范围内（Ar分析为601±9 Ma， He分析为600±2 Ma）。结果表明，He载气的使用显著提高了元素U-Pb比的重现性和精度，在25 × 35µm样品分辨率下，206Pb/238U比的数据收集相对精度为2σ < 1.5%， 207Pb/206Pb比的数据收集相对精度< 2.5%。研究还表明，如果采用适当的方法，与LA-ICP-MS U-Pb测年相关的各种不确定性来源并不排除获得精确和准确年龄结果的可能性。
The analytical potential of a 213 nm laser system coupled to a quadrupole based ICP-MS for U-Pb dating of zircon is investigated. The study was performed on zircons from a Neoproterozoic granitoid of the Cadomian belt of Brittany. Seven zircon fractions of the same sample including two single grains were dated by ID-TIMS to obtain a reference age and error to evaluate the accuracy and precision of LA-ICP-MS U-Pb results. The best estimate for the age of crystallisation obtained by ID-TIMS is 603 ± 2 Ma. LA-ICP-MS analyses were conducted in two sessions, one using only Ar as carrier gas and one using Ar + He. In both cases the age results are within analytical uncertainty of the ID-TIMS age (601 ± 9 Ma for the Ar analyses and 600 ± 2 Ma for the He analyses). It is demonstrated that the use of He carrier gas significantly improves reproducibility and precision of the elemental U-Pb ratios and allows the collection of data with a 2σ relative precision < ca. 1.5% for 206Pb/238U ratios and < ca. 2.5% for 207Pb/206Pb ratios at ca. 25 × 35 µm sample resolution. It is also demonstrated that the various sources of uncertainty associated with LA-ICP-MS U-Pb dating do not preclude the possibility of obtaining precise and accurate age results if an appropriate methodology is applied.