The in situ (U-Th-Sm)/He and U/Pb laser-ablation double-dating procedure is a valuable method that can provide a large dataset relatively efficiently in contrast with conventional bulk helium thermochronometry. In this study, we evaluate the potential age error associated with the double ablation procedure and report the in situ (U-Th-Sm)/He double-ablation dating of 249 zircons from the Fish Canyon Tuff locality. With LA-ICP-MS pseudo-depth profiling and 3D numerical modelling, we show that the concentric double-ablation procedure in minerals with U-Th-Sm zoning can generate a significant (U-Th-Sm)/He age error (positive or negative), resulting in over-scattering and/or an offset of the mean age. Pseudo-depth profiling is insufficient to predict the individual age error, partly because of the superimposed ablations. To evaluate the consequence of this inherent bias, we confront a synthetic age distribution to the error expected for U-Th-Sm zoned zircons analysed with double-ablation (U-Th-Sm)/He thermochronometry. As expected, a strong age bias causes the spreading of peak ages, downgrading the original signal. Yet, the throughput of the ablation-based method can allow intra- and inter-sample peak age identification and comparison, and the coupling of (U-Th-Sm)/He and U/Pb ages extends our ability to deconvolute a multimodal age spectrum.

中文翻译：

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激光烧蚀 (U-Th-Sm)/He 定年锆石：分析年龄偏差及其对研究碎屑锆石种群的影响

原位(U-Th-Sm)/He 和 U/Pb 激光烧蚀双测年程序是一种有价值的方法，与传统的散装氦热计时法相比，它可以相对有效地提供大型数据集。在这项研究中，我们评估了与双重消融程序相关的潜在年龄误差，并报告了原位(U-Th-Sm)/He 对鱼峡谷凝灰岩地区的 249 颗锆石进行双烧蚀测年。通过 LA-ICP-MS 伪深度剖析和 3D 数值模拟，我们表明在具有 U-Th-Sm 分带的矿物中进行同心双烧蚀过程会产生显着的 (U-Th-Sm)/He 年龄误差（正或负数），导致过度分散和/或平均年龄偏移。伪深度剖析不足以预测个体年龄误差，部分原因是叠加的消融。为了评估这种固有偏差的后果，我们面对用双烧蚀 (U-Th-Sm)/He 热计时法分析的 U-Th-Sm 分区锆石预期误差的合成年龄分布。正如预期的那样，强烈的年龄偏差会导致峰值年龄的扩散，从而降低原始信号的等级。然而，