Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue–Caviahue Volcanic Complex (Argentina)

Abstract

The north-western sector of Caviahue caldera (Argentina), close to the active volcanic system of Copahue, is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions, anomalous soil diffuse degassing of CO 2 and hot soils. In March 2014, measurements of soil CO 2 fluxes in 5 of these sites (namely, Las Máquinas, Las Maquinitas I, Las Maquinitas II, Anfiteatro, and Termas de Copahue) allowed an estimation that 165 t of deeply derived CO 2 is daily released. The gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges. Gas equilibria within the H-C-O gas system indicate the presence of a large, probably unique, single phase vapor zone at 200-210°C feeding the hydrothermal manifestations of Las Máquinas, Las Maquinitas I and II and Termas de Copahue. A natural thermal release of 107 MW was computed by using CO 2 as a tracer of the original vapor phase. The magmatic signature of the incondensable fumarolic gases, the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the Caviahue caldera.

Spatial and Depth‐Dependent Variations in Magma Volume Addition and Addition Rates to Continental Arcs: Application to Global CO2 Fluxes since 750 Ma

“…Using these broad assumptions, we can estimate global arc CO 2 fluxes since 750 Ma using MARs, published estimates of global continental arc lengths and a range of arc widths (Figure 4). We also note that mantle CO 2 degasses not solely through volcanic craters but also diffusely through extensional fault systems , through large hydrothermal areas (Werner & Brantley, 2003) and on the flanks and hydrothermal areas of volcanic systems (e.g., Chiodini et al, 2015;Salazar et al, 2004). Overall, diffuse degassing through faults has long been recognized as efficient and significant contribution to the global mantle-derived CO 2 budget (Mörner & Etiope, 2002).…”

“…Blundy et al (2010) used arc melt inclusion CO 2 contents and degassing and crystallization modeling to obtain initial magma CO 2 contents of ≥1.5 wt.%. We also note that mantle CO 2 degasses not solely through volcanic craters but also diffusely through extensional fault systems , through large hydrothermal areas (Werner & Brantley, 2003) and on the flanks and hydrothermal areas of volcanic systems (e.g., Chiodini et al, 2015;Salazar et al, 2004). Using these broad assumptions, we can estimate global arc CO 2 fluxes since 750 Ma using MARs, published estimates of global continental arc lengths and a range of arc widths (Figure 4).…”

Structural architecture releasing deep-sourced carbon dioxide diffuse degassing at the Caviahue – Copahue Volcanic Complex

“…A detailed diffuse degassing survey had already been done in the thermal areas of this volcanic complex and its results were published in Chiodini et al (2015). The results of this paper shed new light on the efflux of CO 2 over the surface not only of the thermal areas, but of a bigger zone that encompasses all thermal sites and represents a high conductivity zone of hot fluid circulation (JICA-EPEN, 1992).…”

Source model for the Copahue volcano magma plumbing system constrained by InSAR surface deformation observations

“…Copahue's high 3 He/ 4 He and CO 2 / 3 He ratios suggest that it is influenced by its extensional setting, with magmas reflecting mantle asthenospheric upwelling and subducted sediments [ Agusto et al ., ]. The high fumarolic gas flux beneath the NE flank of Copahue and the broad area affected are compatible with a large magmatic source beneath this area [ Chiodini et al ., ]. This activity has led to extensive hydrothermal alteration, suggesting that edifice flank instability is a potential hazard [ Varekamp et al ., ].…”