Simultaneous determinations of U–Pb age, Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple-collector ICP-MS
Simultaneous determinations of U–Pb age, Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple-collector ICP-MS
复制标题
DOI：
10.1016/j.chemgeo.2007.10.003
复制
发表时间：
2008-01
期刊：
影响因子：
3.9
通讯作者：
Honglin Yuan;Shan Gao;M. Dai;C. Zong;D. Günther;G. Fontaine;Xiaoming Liu;Chunrong Diwu
中科院分区：
文献类型：
--
作者：
Honglin Yuan;Shan Gao;M. Dai;C. Zong;D. Günther;G. Fontaine;Xiaoming Liu;Chunrong Diwu
我们描述了一种同时测量锆石U-Pb-Hf同位素和微量元素组成的原位方法，该方法使用连接到单个准分子激光烧蚀系统的四极杆和多收集器电感耦合等离子体质谱计（分别为Q-ICP-MS和MC-ICP-MS）。激光产生的锆石气溶胶在烧蚀单元后面通过y形连接器分裂成两个传输管，并同时引入两个质谱仪。用MC-ICP-MS仪测定铪同位素，用Q-ICP-MS仪测定U-Pb年龄和微量元素组成。采用91500、Temora-2、GJ-1、Mud Tank、BR266和Monastery 6种常用锆石标准，对该方法的精密度和准确度进行了评价。斑点尺寸分别为32、44和60 μm。在44 μm和60 μm点上，6颗锆石的U-Pb年龄、Hf同位素和稀土元素组成与推荐/报道值一致，误差在2σ以内。分离式流动测量与Q-ICP-MS分别获得的206pb /238U年龄的相对标准偏差（RSD）差异在91500、Temora-2和GJ-1的相对标准偏差在20%以内，Mud Tank的相对标准偏差在60%以内（由于其较低的U和Pb浓度）。我们的方法为确定一次烧蚀事件中锆石的U-Pb年龄、Hf同位素和微量元素组成提供了一种精确的方法。这对于分析小锆石或包含复杂分带模式的锆石尤其重要。BR266锆石的稀土元素组成比其他锆石更为均匀，可以作为锆石微探针分析新标准的基准。
We describe an in situ method for simultaneous measurement of U–Pb–Hf isotopes and trace element compositions of zircons using a quadrupole and multiple-collector inductively-coupled-plasma mass spectrometer (Q-ICP-MS and MC-ICP-MS, respectively) connected to a single excimer laser-ablation system. A laser-generated zircon aerosol was split behind the ablation cell into two transport tubes via a Y-shaped connector and simultaneously introduced into the two mass spectrometers. Hafnium isotopes were measured on the MC-ICP-MS instrument, while U–Pb ages and trace element compositions were determined using the Q-ICP-MS. The precision and accuracy of this method was evaluated using six well-known and widely used zircon standards (91500, Temora-2, GJ-1, Mud Tank, BR266 and Monastery). Analyses were carried out using spot sizes of 32, 44 and 60 μm. For the 44 and 60 μm spot, the resulting U–Pb ages, Hf isotopic and rare earth element (REE) compositions of these six zircons agree with recommended/reported values within 2σ error. The difference in relative standard deviations (RSD) of206Pb/238U ages between split-flow measurements and those obtained separately on the Q-ICP-MS is within ∼20% for 91500, Temora-2 and GJ-1, and ∼60% for Mud Tank (due to its lower U and Pb concentrations). Our method provides a precise approach for determining the U–Pb age and the Hf isotopic and trace element compositions of zircon within a single ablation event. This is in particular important for analysis of zircons that are small or contain complicated zoning patterns. Finally, the REE composition of zircon BR266 is more homogeneous than other zircons and could be a suitable standard by which to benchmark new standards for microprobe analyses of zircons.