ABSTRACT

Composite volcanoes can progressively weaken through hydrothermal alteration, which may lead to volcano collapse, forming far-reaching debris avalanches. This work reviews and synthesises the type and extent of hydrothermal alteration on Mt. Ruapehu, New Zealand, from rock mechanical, mineralogical, hyperspectral imaging and aero-magnetic studies for input into the first debris avalanche models of Mt. Ruapehu. Mt. Ruapehu shows surface weathering processes, forming goethite, hematite and phyllosilicate assemblages, and hydrothermally altered rock, with phyllosilicate, Fe- oxides and sulphates, pyrite, jarosite, alunite, anhydrite and sulphur. The surface alteration mapped by hyperspectral remote sensing is linked to the deep-seated (≤500 m) alteration by aero-magnetic inversion modelling. Textural analysis and mapping show that alteration weathering and porosity distribution are a result of the both the primary lithology, age, and location relative to active or fossil hydrothermal systems. The synthesis of the aero-magnetic data, previous magnetotelluric models, hyperspectral and hydrothermal mapping, and rock mechanics studies enabled the construction of a schematic model to provide inputs for modelling potential flank failure zones. These models suggest that the southwest and west flanks of Mt. Ruapehu have the highest probability of collapsing and generating debris avalanches.

摘要

复合火山可以通过热液蚀变逐渐减弱，这可能导致火山坍塌，形成影响深远的碎片雪崩。这项工作回顾和综合了山上热液蚀变的类型和程度。新西兰鲁阿佩胡，来自岩石力学、矿物学、高光谱成像和航空磁学研究，用于输入 Mt. 的第一个碎片雪崩模型。鲁阿佩胡。公吨。Ruapehu 显示出地表风化过程，形成针铁矿、赤铁矿和页硅酸盐组合，以及热液蚀变岩石，含有页硅酸盐、Fe-氧化物和硫酸盐、黄铁矿、黄钾铁矾、明矾石、硬石膏和硫磺。高光谱遥感测绘的地表蚀变与航磁反演建模的深部（≤500 m）蚀变有关。结构分析和绘图显示蚀变风化和孔隙度分布是主要岩性、年龄和相对于活动或化石热液系统的位置的结果。航磁数据、以前的大地电磁模型、高光谱和热液测绘以及岩石力学研究的综合使得能够构建示意图模型，为潜在的侧翼破坏区建模提供输入。这些模型表明 Mt. 的西南和西侧。Ruapehu 坍塌和产生碎片雪崩的可能性最高。高光谱和热液测绘以及岩石力学研究能够构建示意图模型，为潜在的侧翼破坏区建模提供输入。这些模型表明 Mt. 的西南和西侧。Ruapehu 坍塌和产生碎片雪崩的可能性最高。高光谱和热液测绘以及岩石力学研究能够构建示意图模型，为潜在的侧翼破坏区建模提供输入。这些模型表明 Mt. 的西南和西侧。Ruapehu 坍塌和产生碎片雪崩的可能性最高。