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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Fluid circulation and structural discontinuities inside Misti volcano (Peru) inferred from self-potential measurements
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Fluid circulation and structural discontinuities inside Misti volcano (Peru) inferred from self-potential measurements

机译：根据自势测量推断米斯蒂火山（秘鲁）内部的流体循环和结构不连续性

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摘要

One of the seven potentially active andesite stratovolcanoes in southern Peru, Misti (5822 m), located 17 km northeast and 3.5 km above Arequipa, represents a major threat to the population ( ～ 900,000 inhabitants). Our recent geophysical and geochemical research comprises an extensive self-potential (SP) data set, an audio-magnetotelluric (AMT) profile across the volcano and CO_2 concentrations in the soil along a radial profile. The SP survey is the first of its kind in providing a complete mapping of a large andesitic stratovolcano 20 km in diameter. The SP mapping enables us to analyze the SP signature associated with a subduction-related active volcano. The general SP pattern of Misti is similar to that of most volcanoes with a hydrogeologic zone in the lower flanks and a hydrothermal zone in the upper central area. A quasi-systematic relationship exists between SP and elevation. Zones with constant SP/altitude gradients (Ce) are observed in both hydrogeologic (negative Ce) and hydrothermal (positive Ce) zones. Transition zones between the different Ce zones, which form a concentric pattern around the summit, have been interpreted in terms of lateral heterogeneities in the lithology. The highest amplitudes of SP anomalies seem to coincide with highly resistive zones. The hydrothermal system 6 km in diameter, which extends over an area much larger than the summit caldera, may be constrained by an older, concealed collapse caldera. A sealed zone has apparently developed through alteration in the hydrothermal system, blocking the migration of CO_2 upward. Significant CO_2 emanations are thus observed on the lower flanks but are absent above the hydrothermal zone.
机译：秘鲁南部的米斯蒂（5822 m）是秘鲁南部的七个潜在活跃的安山岩平流层火山之一，位于东北17公里，比阿雷基帕高3.5公里，对人口（约90万居民）构成了重大威胁。我们最近的地球物理和地球化学研究包括广泛的自势（SP）数据集，横跨火山的声磁大地电磁（AMT）剖面以及沿径向剖面的土壤中CO_2浓度。 SP勘测是首次提供直径20 km的大型安第斯山平流层火山的完整地图。 SP映射使我们能够分析与俯冲相关的活火山相关的SP签名。 Misti的一般SP模式与大多数火山相似，大部分火山的下部侧面有水文地质区，而上部中央区域有热液区。 SP与高程之间存在准系统关系。在水文地质（负Ce）和热液（正Ce）区域均观察到具有恒定SP /高度梯度（Ce）的区域。已经根据岩性的横向异质性解释了不同Ce区域之间的过渡区域，这些过渡区域在山顶周围形成了同心圆型。 SP异常的最大幅度似乎与高阻带一致。直径为6 km的热液系统所延伸的区域比顶峰火山口大得多，它可能受到较旧的隐藏式坍塌火山口的约束。显然通过热液系统的变化形成了一个封闭带，阻止了CO_2向上迁移。因此，在下部侧面观察到了明显的CO_2散发，但在热液区上方却没有。

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