High spatial resolution in situ U-Pb dating using laser ablation multiple ion counting inductively coupled plasma mass spectrometry (LA-MIC-ICP-MS)
High spatial resolution in situ U-Pb dating using laser ablation multiple ion counting inductively coupled plasma mass spectrometry (LA-MIC-ICP-MS)
复制标题
使用激光烧蚀多离子计数电感耦合等离子体质谱 (LA-MIC-ICP-MS) 进行高空间分辨率原位 U-Pb 定年
DOI：
10.1039/c6ja00387g
复制
发表时间：
2017
影响因子：
3.4
通讯作者：
Huang Chao
中科院分区：
文献类型：
--
作者：
Xie Lie Wen;Yang Jin Hui;Yin Qing Zhu;Yang Yue Heng;Liu Jing Bo;Huang Chao
激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）是一种功能强大的微量分析工具，由于其能够快速、精确地原位分析同位素，典型的空间分辨率为30-80 μ m，因此在地球科学中得到了广泛的应用。本文介绍了一种利用193 nm ArF准分子激光烧蚀系统与多离子计数电感耦合等离子体质谱（LA-MIC-ICP-MS）联用的锆石U-Pb定年新方法。当使用小离子束（<12.5 mV）时，离子计数器具有明显的优势，可以用<0.5 mV的238 U信号以更高的空间分辨率测定锆石的年代。通过对32 ~ 2060 Ma的6个锆石标准样品的研究，对新方法进行了评价。利用该技术，我们获得了206 Pb/238 U年龄加权平均值的精度（2s）在1%以内，与标称参考年龄偏差小于1%的精度。我们进一步证明了新的高空间分辨率技术的实用性和鲁棒性，其应用于复杂的锆石分带的真实的地质问题，以确定著名的大别山超压变质作用的年龄。我们预计，该方法将有广泛的应用在高分辨率U-Pb测年的微小或复杂的锆石颗粒与小核心或相对狭窄的区域，在地质研究界的高效率和吞吐量。
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is a powerful micro-analytical tool that has been widely used in geoscience because of its ability to rapidly and precisely analyze isotopes in situ with a typical spatial resolution of 30–80 microns. Here we present a new method for U–Pb dating of zircon with a higher spatial resolution at a scale of 5.8–7.4 μm in diameter and <3 μm in sampling depth (<0.5 ng of zircon material consumption), using a 193 nm ArF excimer laser ablation system coupled with multiple ion counting inductively coupled plasma mass spectrometry (LA-MIC-ICP-MS). Ion counters have an obvious advantage when using a small ion beam (<12.5 mV) and make it possible to date zircons with a 238U signal of <0.5 mV with improved spatial resolution. The new technique was evaluated by investigating six zircon standards with various known ages ranging from 32 Ma to 2060 Ma. Using this technique, we obtained a precision (2s) for the weighted mean 206Pb/238U age within 1% and an accuracy of <1% offset to the nominal reference age. We then further demonstrated the utility and robustness of the new high spatial resolution technique for its application to the real geological problem of complexly zoned zircons, to determine the age of the famous Dabie ultrahigh pressure metamorphism. We anticipate that the method will have a wide range of applications in high-resolution U–Pb dating of tiny or complex zircon grains with small cores or relatively narrow zones, with high efficiency and throughput in the geological research community.