Fluid circulation in a complex volcano-tectonic setting,inferred from self-potential and soil CO2 flux surveys: The Santa María–Cerro Quemado–Zunil volcanoes and Xela caldera (Northwestern Guatemala) |
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| Authors: | Laura Bennati Anthony Finizola James A Walker Dina L Lopez I Camilo Higuera-Diaz Claudia Schütze Francisco Barahona Rafael Cartagena Vladimir Conde Renan Funes Cristobal Rios |
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| Institution: | 1. Risk Frontiers, Faculty of Science, Macquarie University, Australia;2. Commonwealth Scientific and Industrial Research Organisation, Australia;1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an, China;2. Shaanxi Provincial Key Laboratory of Accelerator Mass Spectrometry Technology and Application, Xi''an AMS Center, Xi''an, China;3. University of Chinese Academy of Sciences, Beijing, China;4. Beijing Normal University, Joint Center For Global Changes Studies (JCGCS), Beijing, China;1. Dipartimento di Scienze della Terra, SAPIENZA Università di Roma, P.le A. Moro, 5, 00185 Roma, Italy;2. IGAG-CNR Istituto di Geologia Ambientale e Geoingegneria, Area della Ricerca Roma 1, Via Salaria km 29.300, 00016 Monterotondo Stazione Roma, Italy;3. ISPRA, Istituto Superiore Istituto Superiore per la Protezione e la Ricerca Ambientale, Via Vitaliano Brancati, 48, Roma, Italy;4. Istituto di Scienze Marine, ISMAR-CNR, Via Gobetti 101, 40129 Bologna, Italy;5. Dipartimento di Ingegneria Civile, Edile e Ambientale, SAPIENZA Università di Roma, Via Eudossiana 18, 00184 Roma, Italy;1. South Andes Volcano Observatory, Geological and Mining Chilean Service, Rudecindo Ortega 03850, Temuco, Chile;2. Departamento de Ciencias Físicas, Universidad de la Frontera, casilla 54-D, Temuco, Chile;1. School of Earth Sciences, Wills Memorial Building, University of Bristol, Queens Road, Bristol BS8 1RJ, United Kingdom;2. Department of Geological and Mining Engineering and Sciences, Michigan Technological University (MTU), 630 Dow Environmental Sciences, 1400 Townsend Drive, Houghton, MI 49931, United States of America;3. Instituto Nacional de Sismología, Vulcanología, Meteorología e Hidrología (INSIVUMEH), Edificio Central, 7a. Avenida 14-57 Zona 13, Guatemala, Guatemala;4. Dipartimento di Scienze della Terra, Università degli studi di Torino, Via Valperga Caluso 35, 10125 Torino, Italy |
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| Abstract: | The region encompassing Santa María, Cerro Quemado, and Zunil volcanoes, close to Quetzaltenango, the second largest city of Guatemala, is volcanically and tectonically complex. In addition, the huge Xela caldera, about 20 km in diameter, crosses this area and links up to the important Zunil fault zone located between the three volcanoes. Two highly active geothermal sites, named Zunil-I and Zunil-II, are also located between these three volcanic edifices at the southeastern boundary of Xela caldera. In order to determine the permeability variations and the main structural discontinuities within this complex volcano-tectonic setting, self-potential and soil CO2 flux measurements have been coupled, with a step of 20 m, along a 16.880 km-long profile crossing the entire area. Two shallow hydrothermal systems, with maximum lateral extensions of 1.5 km in diameter, are indicated by positive self-potential/elevation gradients below Santa María and Cerro Quemado volcanoes. Such small hydrothermal systems cannot explain the intense geothermal manifestations at Zunil-I and Zunil-II. Another minor hydrothermal system is indicated by self-potential measurements on the flank of Santa María along the edge of the Xela caldera. CO2 flux measurements display slight variations inside the caldera and decreasing values crossing outside the caldera boundary. We hypothesize the presence of a magmatic body, inside the southeastern border of Xela caldera, to explain the deeper and more intense hydrothermal system manifested by the Zunil-I and the Zunil-II geothermal fields. This magmatic system may be independent from Santa María and Cerro Quemado volcanoes. Alternatively, the hypothesized Xela magmatic system could have a common magmatic origin with the Cerro Quemado dome complex, consistent with previous findings on regional gas emissions. Sectors bordering the Cerro Quemado dome complex also have high amplitude minima-short wavelength anomalies in self-potential, interpreted as preferential rain water infiltration along faults of major permeability, probably related with the most recent stages of Cerro Quemado dome growth. |
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