Fluid circulation and structural discontinuities inside Misti volcano (Peru) inferred from self-potential measurements |
| |
Authors: | Anthony Finizola Jean-Franois Lnat Orlando Macedo Domingo Ramos Jean-Claude Thouret Francesco Sortino |
| |
Institution: | a Laboratoire Magmas et Volcans, Université Blaise Pascal et CNRS, OPGC, IRD, 5 rue Kessler, 63038, Clermont-Ferrand, France;b Instituto Geofísico del Perú, Urbanización La Marina B19, Cayma, Arequipa, Peru;c Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Via Ugo La Malfa, 153, 90144, Palermo, Italy |
| |
Abstract: | 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 CO2 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 CO2 upward. Significant CO2 emanations are thus observed on the lower flanks but are absent above the hydrothermal zone. |
| |
Keywords: | Misti volcano self-potential audio– magnetotelluric electrical resistivity structural discontinuity hydrothermal system Peru |
本文献已被 ScienceDirect 等数据库收录! |
|