Thermal energy release by using CO2 diffuse degassing in the geothermal area of the Copahue ? Caviahue Volcanic Complex

LAMBERTI, M.; CARDELLINI C; CHIODINI G.; AGUSTO M.R.; SZENTIVANYI J.; FORINO P.; NOGUES V.; - CASELLI, A.T.

PUERTO VARAS

Congreso; CITIES ON VOLCANOES 9; 2016

SERNEAGEOMIN

The Copahue ? Caviahue Volcanic Complex (CCVC) is located on the Argentinean ? Chilean border hosting an important magmatic ? hydrothermal system. The development of a project of utilization of a renewable energy, such as the geothermal energy available in this area, could constitute a great benefit for the region around this volcanic complex.In order to contribute to this eventual project, a carbon dioxide soil diffuse degassing survey has been performed over an area of about 1 km2. 1819 measurements were collected over three campaigns carried out in the summers of 2014, 2015 and 2016. The data were elaborated using the Graphical Statistical Approach and the Sequential Gaussian Simulations method (GSA and SGS respectively). By means of the GSA, four log-normal populations were defined at CCVC geothermal field. Out of the entire dataset, 9% of the measured fluxes belong to a population with a CO2 flux mean value of 1421 g m-2 day-1, and it is interpreted to represent a population fed by an endogenous, hydrothermal source. A large uncertainty is associated with this mean value, probably due to the relatively low number of samples available to define this high flux population. The other three populations are interpreted as background populations: with low mean values, 54.5, 6.6 and 4 g m-2 day-1, the CO2 flux related to them is probably related to soil respiration processes. The SGS method was applied in order to map the diffuse degassing structures present in the Caviahue Caldera and to obtain estimates of the total CO2 release. Carbon dioxide anomalies were registered at three out of the four geothermal sites located in the Argentinean side of the CCVC, which are called Las Máquinas, Las Maquinitas and Copahue town. This last locality shows the greatest CO2 soil emissions of the entire surveyed area. The total amount of CO2 released by the whole area of the geothermal field is 208.5 t d-1. Preliminary results by using CO2 as a tracer of the original vapor phase indicate a natural thermal release of up to 100 MW.