岩矿测试Issue(4)：399-407,9.DOI:10.15898/j.cnki.11-2131/td.2015.04.004
LA - MC - ICPMS 分析古老熔体包裹体 Pb 同位素组成中的误差评价
Evaluation of Error Propagation in Lead Isotope Analysis of Ancient Melt Inclusions by LA-MC-ICP-MS
摘要
Abstract
Determination of Pb isotopes in melt inclusions by Laser Ablation -Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry( LA-MC-ICP-MS)is limited to samples formed later than Mesozoic because U and Th signals are not monitored. In this study,Pb isotopic compositions of two reference glasses and ancient melt inclusions which have undergone significant U-Th decay are determined by LA-MC-ICP-MS. The effect of the U/Pb and Th/Pb analytical errors on the calculation of initial Pb isotopic ratios was also evaluated. In the experiment USGS HKT-1 G is used as the external calibrant and a standard-sample-standard bracketing method is used to correct instrument drift and mass bias. Analytical precisions of 208 Pb/ 206 Pb and 207 Pb/206 Pb of USGS standards, BHVO-2G and TB-1G,are better than 0. 30%(2RSD)and both agree within 0. 30% of the preferred values. However,232 Th/ 206 Pb and 238 U/ 206 Pb ratios are highly variable and yield an external precision of 5%. Error propagation calculations indicate that the ages of the samples have significant effects on the errors of the initial lead isotopic ratios. For Phanerozoic samples that are earlier than 540 Ma,even the differences between the measured 232 Th/ 206 Pb and 238 U/ 206 Pb ratios and the real values reach 10%,yet the age-corrected initial lead isotopic ratios are still within 0. 80% deviations relative to the real values. Therefore,the proposed method in this study can determine the lead isotopic compositions of melt inclusions in samples from Cenozoic to Paleozoic,expanding the geological application.关键词
激光剥蚀/多接收器电感耦合等离子体质谱法/熔体包裹体/铅同位素/误差评价Key words
laser ablation/Multiple-collector Inductively Coupled Plasma-Mass Spectrometry/melt inclusion/lead isotope/error evaluation分类
化学化工引用本文复制引用
张乐,任钟元,钱生平,丁相礼,吴亚东..LA - MC - ICPMS 分析古老熔体包裹体 Pb 同位素组成中的误差评价[J].岩矿测试,2015,(4):399-407,9.基金项目
国家重点基础研究发展计划（973计划）项目--二叠纪地幔柱构造与地表系统演变（2011CB808903）；国家自然科学基金--华北克拉通中-新生代镁铁质火山岩的熔体包裹体研究揭示原生岩浆组成、源区性质及岩石圈破坏的动力学机制（91214202）；国家自然科学基金--峨眉山大火成岩省各种成矿岩体的原生岩浆组成熔体包裹体研究 （）
