Structural controls on fluid circulation at the Caviahue-Copahue Volcanic Complex (CCVC) geothermal area (Chile-Argentina), revealed by soil CO2 and temperature, self-potential, and helium isotopes
Author
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Roulleau, Emilie
Author
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Bravo, Francisco
Author
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Pinti, Daniele L.
Author
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Barde Cabusson, Stéphanie
Author
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Pizarro, Marcela
Author
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Tardani, Daniele
Author
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Muñoz, Carlos
Author
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Sánchez, Juan
Author
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Sano, Yuji
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Takahata, Naoto
Author
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Cal, Federico de la
Author
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Esteban, Carlos
Author
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Morata Céspedes, Diego
Admission date
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2019-05-29T13:30:12Z
Available date
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2019-05-29T13:30:12Z
Publication date
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2017
Cita de ítem
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Journal of Volcanology and Geothermal Research 341 (2017) 104–118
Identifier
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03770273
Identifier
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10.1016/j.jvolgeores.2017.05.010
Identifier
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https://repositorio.uchile.cl/handle/2250/168915
Abstract
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Natural geothermal systems are limited areas characterized by anomalously high heat flowcaused by recent tectonic
ormagmatic activity. The heat source at depth is the result of the emplacement ofmagmabodies, controlled
by the regional volcano-tectonic setting. In contrast, at a local scale a well-developed fault-fracture network favors
the development of hydrothermal cells, and promotes the vertical advection of fluids and heat. The Southern
Volcanic Zone (SVZ), straddling Chile and Argentina, has an important, yet unexplored and undeveloped geothermal
potential. Studies on the lithological and tectonic controls of the hydrothermal circulation are therefore important
for a correct assessment of the geothermal potential of the region. Here, new and dense self-potential
(SP), soil CO2 and temperature (T) measurements, and helium isotope data measured in fumaroles and thermal
springs from the geothermal area located in the north-eastern flank of the Copahue volcanic edifice, within the
Caviahue Caldera (the Caviahue-Copahue Volcanic Complex - CCVC) are presented. Our results allowed to the
constraint of the structural origin of the active thermal areas and the understanding of the evolution of the geothermal
system. NE-striking faults in the area, characterized by a combination of SP, CO2, and Tmaxima and high
3He/4He ratios (up to 8.16±0.21Ra,whereas atmospheric Ra is 1.382 × 10−6), promote the formation of vertical
permeability preferential pathways for fluid circulation.WNW-striking faults represent low-permeability pathways
for hydrothermal fluid ascent, but promote infiltration of meteoric water at shallow depths, which dilute
the hydrothermal input. The region is scatteredwith SP, CO2, and Tminima, representing self-sealed zones characterized
by impermeable altered rocks at depth, which create local barriers for fluid ascent. The NE-striking
faults seem to be associated with the upflowing zones of the geothermal system, where the boiling process
produces a high vapor-dominated zone close to the surface, whereas the WNW-striking faults could act as a
boundary of the Copahue geothermal area to the south.
Structural controls on fluid circulation at the Caviahue-Copahue Volcanic Complex (CCVC) geothermal area (Chile-Argentina), revealed by soil CO2 and temperature, self-potential, and helium isotopes