A method for U–Pb isotopic dating using secondary ion mass spectrometer (SIMS) was developed for uraninite. Correlation between ²⁵¹(UO)⁺/²³⁵U⁺ and ²⁰⁶Pb⁺/²³⁵U⁺ obtained by a sensitive high‐resolution ion microprobe (SHRIMP) was adopted for a calibration from secondary ion ratios (Pb⁺/U⁺) to the atomic abundance ratios (Pb/U). In this study, a uraninite sample (²⁰⁶Pb/²³⁸U = 0.1647) collected from Faraday mine, Bancroft, Canada, is used as a reference material for the U–Pb calibration. The established method was applied to three uraninite samples collected from the Chardon, Ecarpière, and Mistamisk mines. The calibrated ²⁰⁶Pb^*/²³⁸U ratios of the three uraninites show correlation with Pb/U elemental ratios obtained using an electron probe microanalyzer (EPMA) (correlation coefficients: 0.98, 0.99, and 0.97, respectively), which indicates the reliability of the SHRIMP calibration method used in this study. The analysis of Ecarpière uraninite provides concordant U–Pb data, and a weighted average of the ²⁰⁶Pb^*/²³⁸U age is 287 Ma ±8 Ma (95 % conf.) which is consistent with the previous chronological results by SIMS. Mistamisk uraninite provides discordant U–Pb data with the upper and lower intercept ages of 1 729 and 421 Ma, which correspond to uraninite formation in association with the Hudsonian orogeny and the remobilization of uranium as pitchblende, respectively. The U–Pb age of Chardon uraninite (315 Ma) is consistent with the igneous activity of Mortagne granite, but is older than the previously reported age (264 Ma). Marcasite in the Chardon uraninite altered to goethite under the oxidizing condition, which indicates that U–Pb system in the uraninite crystallized at 315 Ma was disturbed under the oxidizing condition. The established calibration method using Faraday uraninite is useful for U–Pb isotopic dating on the scale of a few micrometers to tens of micrometers, which make it possible to obtain the accurate age of uraninite.

中文翻译：

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使用二次离子质谱仪开发铀矿的U–Pb定年：参考材料的选择和校准方法的建立

开发了一种用于铀尿石的二次离子质谱仪（SIMS）用于U–Pb同位素定年的方法。通过次级离子离子比（Pb ⁺ / U ⁺）与原子的校准采用了灵敏的高分辨率离子微探针（SHRIMP）获得的²⁵¹（UO）⁺ / ²³⁵ U ⁺和²⁰⁶ Pb ⁺ / ²³⁵ U ⁺之间的相关性。丰度比（Pb / U）。在这项研究中，尿素样品（²⁰⁶ Pb / ²³⁸从加拿大班克罗夫特的法拉第矿收集的U = 0.1647）用作U–Pb校准的参考材料。已建立的方法适用于从Chardon，Ecarpière和Mistamisk矿山收集的三个尿素矿样品。三种尿素的标定²⁰⁶ Pb ^* / ²³⁸ U比值与使用电子探针微分析仪（EPMA）获得的Pb / U元素比值具有相关性（相关系数分别为0.98、0.99和0.97），表明了这种方法的可靠性。本研究中使用的SHRIMP校准方法。Ecarpièreuraninite的分析提供一致的U–Pb数据，以及²⁰⁶ Pb ^* / ²³⁸的加权平均值U年龄为287 Ma±8 Ma（95％conf。），与SIMS先前的年代顺序结果一致。Mistamisk铀矿提供不一致的U-Pb数据，其上，下截距年龄分别为1 729和421 Ma，分别对应于与Hudsonian造山运动和铀迁移为沥青闪石相关的铀矿形成。Chardon uraninite（315 Ma）的U–Pb年龄与Mortagne花岗岩的火成岩活动一致，但比以前报道的年龄（264 Ma）大。在氧化条件下，Chardon铀矿中的钙锰矿转变为针铁矿，这表明在315 Ma下结晶的铀矿中的U–Pb系统受到干扰。