Abstract Continued improvements in both ICPMS (inductively-coupled plasma mass spectrometry) and laser ablation technologies are fueling advancements in accessory mineral investigations and their related isotope systems of interest, and are now being applied to a wide range of geological applications. In this contribution we present an updated methodology for laser ablation split-stream (LASS) analysis of the light rare earth element (LREE) enriched minerals monazite, titanite, and apatite for simultaneous analysis of the U-Th-Pb age (or trace element content) and the Sm-Nd isotope system. The data were collected with the current generation of high-sensitivity ICPMS and laser systems (ThermoFinnigan NeptunePlus MC-ICPMS and Element XR SF-ICPMS- coupled to a RESOlution 193 nm ArF excimer laser system). The increased sensitivity of these ICPMS instruments allows for improved spatial resolution and the ability to target minerals which previously contained insufficient concentrations of elements of interest (e.g., Sm-Nd in apatite), making their analysis difficult, if not impossible, using less sensitive instruments. Furthermore, the higher sensitivity allows less aggressive ablation parameters that facilitate thin section sampling and reduces inter-element and isotopic fractionation. To assess and improve the accuracy, precision, and efficiency of the technique, three new potential LASS reference materials (RMs) are evaluated for dual U-Pb and Sm-Nd analysis (Tory Hill apatite, Tory Hill titanite, and Steenskralkamp monazite). The homogeneity of these materials was first assessed using reconnaissance laser ablation analyses, with final characterization of U-Pb age and Sm-Nd isotope composition using isotope-dilution thermal ionization mass spectrometry (ID-TIMS). The precision and accuracy of the LASS method is explored using secondary mineral reference materials of known age and Sm-Nd isotope composition. The utility of the technique is evaluated with a case study of monazite and apatite from the Eoarchean Uivak Gneiss complex of Labrador, Canada. Finally, we suggest that there is a wide variety of geological applications for this methodology, such as multi-mineral detrital provenance, crustal growth, and petrogenic studies.

中文翻译：

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独居石、钛铁矿和磷灰石的 Sm-Nd 和 U-Pb 同位素组成的激光烧蚀分流分析——改进、潜在参考材料以及在太古宙 Saglek Block 片麻岩中的应用

摘要 ICPMS（电感耦合等离子体质谱法）和激光烧蚀技术的持续改进推动了辅助矿物研究及其相关同位素系统的进步，现在正被广泛应用于地质应用。在这篇文章中，我们提出了一种更新的方法，用于对富含轻稀土元素 (LREE) 的矿物独居石、钛石和磷灰石进行激光烧蚀分流 (LASS) 分析，以同时分析 U-Th-Pb 年龄（或微量元素）含量）和 Sm-Nd 同位素系统。数据是使用当前一代高灵敏度 ICPMS 和激光系统（ThermoFinnigan NeptunePlus MC-ICPMS 和 Element XR SF-ICPMS-耦合到 RESOlution 193 nm ArF 准分子激光系统）收集的。这些 ICPMS 仪器的灵敏度提高，可以提高空间分辨率，并能够定位以前所含目标元素浓度不足的矿物（例如磷灰石中的 Sm-Nd），这使得使用灵敏度较低的仪器进行分析变得困难，如果不是不可能的话. 此外，更高的灵敏度允许不太激进的消融参数，这有助于薄切片采样并减少元素间和同位素分馏。为了评估和提高该技术的准确度、精密度和效率，对三种新的潜在 LASS 参考材料 (RM) 进行了双 U-Pb 和 Sm-Nd 分析（Tory Hill 磷灰石、Tory Hill 钛石和 Steenskralkamp 独居石）评估。这些材料的均匀性首先使用侦察激光烧蚀分析进行评估，使用同位素稀释热电离质谱 (ID-TIMS) 对 U-Pb 年龄和 Sm-Nd 同位素组成进行最终表征。使用已知年龄和 Sm-Nd 同位素组成的次生矿物参考材料探索 LASS 方法的精密度和准确度。通过对加拿大拉布拉多始太古代 Uivak 片麻岩复合体的独居石和磷灰石的案例研究来评估该技术的实用性。最后，我们建议这种方法有多种地质应用，例如多矿物碎屑物源、地壳生长和岩石成因研究。使用已知年龄和 Sm-Nd 同位素组成的次生矿物参考材料探索 LASS 方法的精密度和准确度。通过对加拿大拉布拉多始太古代 Uivak 片麻岩复合体的独居石和磷灰石的案例研究来评估该技术的实用性。最后，我们建议这种方法有多种地质应用，例如多矿物碎屑物源、地壳生长和岩石成因研究。使用已知年龄和 Sm-Nd 同位素组成的次生矿物参考材料探索 LASS 方法的精密度和准确度。通过对加拿大拉布拉多始太古代 Uivak 片麻岩复合体的独居石和磷灰石的案例研究来评估该技术的实用性。最后，我们建议这种方法有多种地质应用，例如多矿物碎屑物源、地壳生长和岩石成因研究。