Structural control on carbon dioxide diffuse degassing at the Caviahue ? Copahue Volcanic Complex, Argentina

LAMBERTI, M.C.; AGUSTO, M.; BARCELONA, H.; VIGIDE, N.; YAGUSPSKY, D.; VELEZ, M.L.; VENTURI, S.; WINOCUR, D.; TASSI, F.

Hamburgo

Conferencia; Latin-American colloquium of geosciences; 2019

Caviahue ? Copahue Volcanic Complex (CCVC) is located within the Andean Cordillera, in the Neuquén province, Argentina. This magmatic system lies within the northern termination of the Liquiñe ? Ofqui fault zone, a 1,200-km-long intra-arc strike-slip fault system. Fluid emissions at this active volcanic complex are fed by a hydrothermal reservoir located at 800 m depth, mostly recharged by meteoric water. The reservoir is heated by a magmatic body located at 5 km depth, which also provides the system with magmatic gases. Fluid emissions at the CCVC release over 200 tons per day of soil diffuse CO2. The aim of this study is to evaluate the control that the local structural scenario exerts on CO2 flow, from the hydrothermal reservoir to the surface. The correlation between diffuse degassing anomalies and geological brittle structures was evaluated by performing a spatial analysis with the use of geochemical and structural data. A total amount of 1,819 measurements of CO2 flux and soil temperature were performed, over an area of ~10 km2. CO2 flux data was processed in order to map the spatial distribution of diffuse emissions. The local structure was characterized by means of satellite images and digital elevation models interpretation.The geochemical analysis showed well-defined CO2 diffuse degassing anomalies in four hydrothermal sites within the CCVC. These anomalies follow clear linear trends that can be clustered in different domains regarding their orientations. The principal domain strikes NE-SW. The analysis of the satellite images and digital elevation models allowed discriminating three sets of structures. The main set is constituted by NE-SW lineaments; the second set is constituted by NW-SE lineaments; the third set is composed by E-W oriented lineaments. Two length-weighted rose diagrams were computed, plotting diffuse degassing anomalies directions and geological brittle structures directions. The similarity of these plots suggests that the main NE-SW structures constitute the preferential pathways for soil diffuse CO2. This also suggests that the two secondary sets act as fluids pathways as well.