Prolonged volcanic activity can induce surface weathering and hydrothermal alteration that is a primary control on edifice instability, posing a complex hazard with its challenges to accurately forecast and mitigate. This study uses a frequently active composite volcano, Mt Ruapehu, New Zealand, to develop a conceptual model of surface weathering and hydrothermal alteration applicable to long‐lived composite volcanoes. The alteration on Mt Ruapehu was classified using ground samples as non‐altered, supergene argillic, intermediate argillic, and advanced argillic. The first two classes have a paragenesis that is consistent with surficial infiltration and circulation of low‐temperature (<40°C) neutral to mildly acidic fluids, inducing chemical weathering and formation of weathering rims on rock surfaces. The intermediate and advanced argillic alteration formed from hotter (≥100°C) hydrothermal fluids with lower pH, interacting with the andesitic to dacitic host rocks. The distribution of weathering and hydrothermal alteration has been mapped with airborne hyperspectral imaging through image classification, while aeromagnetic data inversion was used to map alteration to up to 500‐m depth. The joint use of hyperspectral imaging complements the geophysical methods since it can spectrally identify hydrothermal alteration mineralogy. This study established a conceptual model of hydrothermal alteration history of Mt Ruapehu, exemplifying a long‐lived and nested active and ancient hydrothermal system. This study's combination approach can be used to indicate the most likely sources of future debris avalanches, which are a significant hazard on Ruapehu.

中文翻译：

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复合火山的热​​液蚀变：新西兰鲁阿佩胡山的矿物学，高光谱成像和航磁研究

长时间的火山活动会引起地表风化和热液蚀变，这是建筑物失稳的主要控制因素，带来了复杂的危险，其挑战在于准确预测和缓解。这项研究使用了一个频繁活动的复合火山（新西兰的鲁阿佩胡山）来开发适用于长寿命复合火山的地表风化和热液蚀变的概念模型。鲁阿佩胡山的蚀变使用地面样品分类为未改变，表生argillic，中等argillic和高级argillic。前两类具有共生作用，这与低温（<40°C）中性至中度酸性流体的表面渗透和循环相一致，从而诱发化学风化作用并在岩石表面形成风化边缘。中度和晚期的泥质蚀变是由pH较低的较热（≥100°C）热液形成的，与安山岩到大山状主岩相互作用。风化和热液蚀变的分布已通过图像分类通过航空高光谱成像进行了映射，而航空磁数据反演则被用于将蚀变映射到最大500 m的深度。高光谱成像的联合使用补充了地球物理方法，因为它可以光谱识别水热蚀变矿物学。这项研究建立了鲁阿佩胡山热液蚀变历史的概念模型，举例说明了一个长期且嵌套的活跃而古老的热液系统。这项研究的组合方法可用于指示未来碎片雪崩的最可能来源，