Soil CO2 flux baseline in Planchón - Peteroa Volcanic Complex, Southern Andes, Argentina - Chile

The Planchon´- Peteroa Volcanic Complex exhibits two active degassing areas: Peteroa crater, PC, and peripheralhydrothermal areas, analyzed in three sampling sites, namely Valle Banos~ del Azufre, VBA, Valle del Pen~on, ´ VPand Valle Valenzuela, VZ. This prospective study was designed to investigate the soil diffuse emissions of CO2 atthis volcanic complex. The survey consisted of 560 measurements of CO2 soil diffuse flux and temperaturecarried out at PC, VBA, VP. The results of this work show that diffuse CO2 is emitted at PC through two welldefined diffuse degassing structures and flux distribution that can be modeled by combining two log-normalpopulations. Here, the main source of soil CO2 is a shallow aquifer recharged by steam condensation andmeteoric fluids that interact with rising magmatic gases. The carbon isotopic signature reveals that CO2 diffusedegassing is affected by secondary soil processes during its ascent. The total diffuse CO2 output at the surveyedarea of PC, which covers 77,000 m2 around the crater fumarolic field, is 6.49 ± 0.32 td- 1. Soil diffuse emissionsat the hydrothermal peripheral sites, VBA and VP, were studied covering a total area of 590,000 ? m2. Theseemissions are characterized by poorly defined diffuse degassing structures and flux distributions that can bemodeled by combining three log-normal populations, which suggest that multiple sources feed CO2 diffuseemissions. In concordance, the isotopic analysis also suggests a mixed source of CO2 and degassing affected bysecondary processes that modify the original isotope composition. CO2 soil degassing at VZ shows a clear relationwith the vegetated areas of the soil. The minimum endogenous CO2 output estimation here proposed for thePlanchon´- Peteroa Volcanic Complex is that of PC, -6.5t d- 1. The thermal energy release was computed for PC,and the estimation is 2.57 ± 0.53 MW.