Simultaneous determinations of U–Pb age, Hf isotopes and trace element compositions of zircon by excimer laser-ablation quadrupole and multiple-collector ICP-MS

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• 作者：Hong-Lin Yuan ; Shan Gao ; Meng-Ning Dai ; Chun-Lei Zong ; Detlef Gü ; nther ; Gisela Helene Fontaine ; Xiao-Ming Liu ; ChunRong Diwu
• 关键词：Zircon ; Hf isotopes ; U– ; Pb dating ; Trace elements ; Laser ablation ; ICP-MS
• 刊名：Chemical Geology
• 出版年：2008
• 出版时间：15 January 2008
• 年：2008
• 卷：247
• 期：1-2
• 页码：100-118
• 全文大小：3531 K

文摘

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) of ²⁰⁶Pb/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.