213 nm Nd-YAGレーザーアブレーションICP質量分析装置を用いたジルコンのU-Pb局所年代分析：SHRIMPデータとの整合性の検討

概要

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Laser ablation–inductively coupled plasma-mass spectrometry (LA-ICP-MS) is a powerful tool for rapid and precise U-Pb zircon age dating. Here, we report U-Pb ages for detrital zircons determined using 213 nm Nd-YAG LA-ICP-MS analysis, and compare these results with those determined using a sensitive high-resolution ion microprobe (SHRIMP) to evaluate approaches for detrital zircon age dating during provenance analysis. Consistency of the system was assessed by measuring four well-characterized standard zircon samples (Plešovice, SL13, AS3, QGNG), with weighted mean measured 206Pb/238U and 207Pb/206Pb ages of the samples only slightly offset from the reference ages and with acceptable MSWD values, barring the 207Pb/206Pb age of the Plešovice zircon, which had a low 207Pb signal intensity. Detrital zircon grains were re-measured by LA-ICP-MS to assess consistency between the LA and SHRIMP systems, with 207Pb/206Pb ages for zircons older than 1000 Ma in excellent agreement with SHRIMP ages; typical offsets were between −3.9% and 0.3%. In addition, zircons younger than 1000 Ma had more accurate 206Pb/238U than 207Pb/206Pb ages. Both LA-ICP-MS and SHRIMP techniques produce results that are in excellent agreement, barring a few analyses that were affected by zircon heterogeneity or zoning.