Wolframite has been proposed as a U/Pb geochronometer for direct dating of W mineralisation events, but its isotopic analysis may be hampered by highly variable and low U contents (<200 ppm) and low ²⁰⁶Pb/²⁰⁴Pb ratios (〈300), heterogenous common Pb compositions, post-crystallisation alteration, and the presence of non-cogenetic mineral and fluid inclusions. In situ U/Pb dating of wolframite by laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS) can avoid these analytical challenges but requires reference materials to properly correct for matrix and instrumental effects on measured U/Pb ratios. This study presents the U/Pb systematics by LA-ICP-MS of a wolframite sample (MTM-1) from the French Massif Central (FMC) which has been considered for normalisation and validation purposes of U/Pb LA-ICP-MS wolframite data in previous studies. We demonstrate that the MTM-1 wolframite is chemically and isotopically heterogeneous, and more importantly, we show that the previously defined ID-TIMS U/Pb age (334.4 ± 1.7 Ma, 2σ) is invalid due to an inappropriate common Pb correction. We calculate a new U/Pb crystallisation age of 316.7 ± 5.8 Ma (2σ). Based on our new calibration, we also present the U-Th-Pb trace element and U/Pb ages of six W deposits from the FMC, also previously studied by ID-TIMS. We show that U/Pb ages determined by LA-ICP-MS are more robust and geological plausible compared to ID-TIMS ages obtained on the same samples. The concentrations of U (ca 0.1–150 ppm) and Pb (ca 0.01–90 ppm) in FMC wolframite are highly variable and do not ubiquitously correlate to major element composition (such as the Fe/(Fe + Mn) ratio). The chemical variability and isotopic heterogeneity observed in wolframite from the FMC highlights the importance of pre-screening imaging methods (e.g., SEM, EPMA, μXRF) prior to LA-ICP-MS U/Pb analyses. Based on our results, we propose new guidelines for U/Pb LA-ICP-MS wolframite geochronology to increase accuracy and reproducibility in age determinations, as well as improving interlaboratory comparisons.

黑钨矿已被提议作为 U/Pb 年代计用于 W 矿化事件的直接测年，但其同位素分析可能受到高度可变和低 U 含量 (<200 ppm) 和低²⁰⁶ Pb/ ^{204 的}阻碍Pb 比率 (<300)、不均匀的常见 Pb 成分、结晶后改变以及非共生矿物和流体包裹体的存在。通过激光烧蚀 - 电感耦合等离子体 - 质谱法 (LA-ICP-MS) 对黑钨矿进行原位 U/Pb 测年可以避免这些分析挑战，但需要参考材料正确校正基质和仪器对测量 U/Pb 比的影响。本研究展示了来自法国地块中心 (FMC) 的黑钨矿样品 (MTM-1) 的 LA-ICP-MS 的 U/Pb 系统学分析，该样品已被考虑用于 U/Pb LA-ICP-MS 黑钨矿的标准化和验证目的以往研究中的数据。我们证明了 MTM-1 黑钨矿在化学和同位素上是异质的，更重要的是，我们证明了先前定义的 ID-TIMS U/Pb 年龄（334.4 ± 1.7 Ma，2σ) 由于不适当的公共铅校正而无效。我们计算出新的 U/Pb 结晶年龄为 316.7 ± 5.8 Ma (2σ)。基于我们的新校准，我们还展示了来自 FMC 的六个 W 沉积物的 U-Th-Pb 痕量元素和 U/Pb 年龄，之前也由 ID-TIMS 研究过。我们表明，与在相同样品上获得的 ID-TIMS 年龄相比，由 LA-ICP-MS 确定的 U/Pb 年龄更可靠且地质可信度更高。U (FMC 黑钨矿中的约0.1–150 ppm) 和 Pb (约0.01–90 ppm) 变化很大，并且与主要元素组成（例如 Fe/(Fe + Mn) 比率）并不普遍相关。在 FMC 的黑钨矿中观察到的化学变异性和同位素异质性突出了在 LA-ICP-MS U/Pb 分析之前预筛选成像方法（例如，SEM、EPMA、μXRF）的重要性。根据我们的结果，我们提出了 U/Pb LA-ICP-MS 黑钨矿年代学的新指南，以提高年龄测定的准确性和可重复性，并改进实验室间比较。