Accurate and precise dating of Quaternary lavas and pyroclastic flow or fall deposits is essential for understanding the evolution of active volcanoes and providing context for future eruptions and hazard assessment. The ⁴⁰Ar/³⁹Ar method is commonly employed to date these volcanic materials, however, dating young (<150 ka) K₂O-poor materials can be challenging owing to low radiogenic ⁴⁰Ar* contents that can be difficult to distinguish from trapped atmospheric argon. To address this challenge, a collaborative intercalibration exercise involving the University of Wisconsin-Madison WiscAr Laboratory and the ⁴⁰Ar/³⁹Ar Laboratory of the Servicio Nacional de Geología y Minería (SERNAGEOMIN), Chile was conducted on a common set of samples with the aim of refining our methods and optimizing precision and accuracy of age determinations. Groundmass and plagioclase samples were analyzed on a 5-collector Noblesse ion counting mass spectrometer in the WiscAr lab, whereas measurements in the SERNAGEOMIN lab were performed using an ARGUS VI spectrometer equipped with faraday detectors and one compact discrete dynode electron multiplier. Samples for the intercalibration were collected jointly from three Andean Southern Volcanic Zone volcanoes to evaluate the capability of each laboratory to date different materials. Samples from lava flows with 1.0–3.2 wt % K₂O from Planchon-Peteroa volcanic complex and with <1.0 wt % K₂O from Calbuco Volcano that are the focus of ongoing geological studies were measured in both laboratories. Single crystals of plagioclase (0.6–1.0 wt% K₂O) were measured from the voluminous Diamante (Pudahuel) ignimbrite sourced from the Diamante Caldera. Multiple rounds of experiments were conducted including co-irradiation of samples at Oregon State University, as well as irradiations using the CCHEN reactor in Chile to investigate differences in neutron fluence parameters. As a result, SERNAGEOMIN has modified long-used protocols for the CCHEN reactor so that Quaternary samples may be irradiated for periods of time most appropriate for their age. Although less precise than plateau ages, the isochron ages generated in the two laboratories agree at 2σ for each sample. Six of six co-irradiated samples from Planchon-Peteroa yield plateau ages that also show inter-lab agreement at 2σ. The low K₂O lavas from Calbuco proved more challenging with only three out of five plateau ages in agreement between labs. SERNAGEOMIN blanks were higher and more variable in Calbuco experiments, thus, differences in the variability of the measured ³⁶Ar blanks between the two laboratories may explain the discrepancy in plateau ages. Analysis of single plagioclase crystals from the Diamante Ignimbrite show excellent agreement between labs for both weighted mean apparent ages and isochron ages. We favor an isochron age for the ignimbrite of 132.4 ± 2.2 ka, however, discrepancies in results between samples from three different outcrops present an interesting geochronologic problem that warrants further study. Overall, the consistency of the results between labs is promising. These new precise age determinations significantly improve our understanding of the temporal evolution of these active volcanoes.

第四纪熔岩和火山碎屑流或秋季沉积物的准确定年对于了解活火山的演化以及为未来的喷发和灾害评估提供背景至关重要。通常采用⁴⁰ Ar/ ³⁹ Ar 方法对这些火山材料进行测年，但是，由于难以将放射性⁴⁰ Ar* 含量与被困火山材料区分开来，因此对年轻 (<150 ka) 贫 K ₂ O 材料进行测年可能具有挑战性。大气氩。为了应对这一挑战，威斯康星大学麦迪逊分校 WiscAr 实验室和⁴⁰ Ar/ ³⁹Servicio Nacional de Geología y Minería (SERNAGEOMIN) 的 Ar 实验室对一组通用样品进行了研究，目的是改进我们的方法并优化年龄测定的精度和准确性。在 WiscAr 实验室的 5 收集器 Noblesse 离子计数质谱仪上分析了地块和斜长石样品，而在 SERNAGEOMIN 实验室中使用配备法拉第探测器和一个紧凑型离散打拿极电子倍增器的 ARGUS VI 光谱仪进行测量。相互校准的样本是从三个安第斯南部火山区火山联合收集的，以评估每个实验室对不同材料进行年代测定的能力。_{来自 Planchon-Peteroa 火山复合体的 1.0–3.2 wt % K 2} O 和 <1.0 wt % K的熔岩流样品_{来自 Calbuco Volcano 的2} O是正在进行的地质研究的重点，在两个实验室都进行了测量。斜长石单晶 (0.6–1.0 wt% K ₂O) 是从来自 Diamante Caldera 的大量 Diamante (Pudahuel) 点火岩中测量的。进行了多轮实验，包括在俄勒冈州立大学对样品进行联合辐照，以及使用智利的 CCHEN 反应堆进行辐照以研究中子注量参数的差异。因此，SERNAGEOMIN 修改了 CCHEN 反应器长期使用的协议，以便第四纪样品可以在最适合其年龄的时间段内进行辐照。虽然不如高原年龄精确，但两个实验室生成的等时线年龄在每个样品的 2σ 上一致。来自 Planchon-Peteroa 的六个共同辐照样品中的六个产生了高原年龄，这些样品也显示了 2σ 的实验室间一致性。低 K ₂事实证明，来自 Calbuco 的 O lavas 更具挑战性，实验室之间只有五分之三的高原年龄达成一致。在 Calbuco 实验中，SERNAGEOMIN 空白更高且变化更大，因此，测量的³⁶两个实验室之间的 Ar 空白可以解释高原年龄的差异。对来自 Diamante Ignimbrite 的单个斜长石晶体的分析表明，实验室之间的加权平均表观年龄和等时线年龄非常一致。我们赞成 132.4 ± 2.2 ka 的等时线年龄，然而，来自三个不同露头的样品之间的结果差异提出了一个有趣的地质年代学问题，值得进一步研究。总体而言，实验室之间结果的一致性是有希望的。这些新的精确年龄确定显着提高了我们对这些活火山的时间演化的理解。