Resumo

SANCI, Romina; PANARELLO, Héctor O.  e  OSTERA, Héctor A.. Carbon dioxide flux in the eastern flank of Peteroa volcano, Southern Andes. Rev. mex. cienc. geol [online]. 2010, vol.27, n.2, pp.225-237. ISSN 2007-2902.

This work reports the first results of CO₂ flux associated to the volcanic activity of the Planchón-Peteroa volcanic complex, Mendoza province, Argentina. The survey was carried out in the valley of arroyo Los Baños, in the eastern lank of the Peteroa volcano, where evidence of volcanic activity is found (Termas o Baños del Azufre). The CO₂ fluxes were quantified applying the so-called dynamic closed chamber method, wich was previously calibrated in the laboratory. CO₂ luxes ranged from 6 g/m²day to 114 g/m²·day; they were log-normally distributed and they were fitted to a logarithmical model with nugget effect when the variograms were applied. The cumulative probability plot showed three different flux populations with means of 13 g/m²·day (background soil gases) and 29 g/m²·day and 83 g/m²·day (anomalous gases). These anomalous values, which correlated positively with the land temperature, would be related to the magmatic degassing of the complex, since they were registered in the same topographic level that the hot springs, wich showed total dissolved inorganic carbon (TDIC) -δ¹³C between -11.7 ‰ to -9.6 ‰, corresponding to the interaction of the water with fluids associated to gases of magmatic origin. Isotope data of δ¹⁸O (~ -14 ‰) and δ²H (~ -106 ‰) of these water samples indicated a main contribution of meteoric waters; this suggests that in the valley of arroyo Los Baños, melt waters infiltrate into the ground and are warmed up by hot subsoil gases. In this valley, the ascent of CO₂ gives rise to two manifestations as follows: direct emissions through the hot springs and diffuse emissions through the alluvial deposits.

Palavras-chave : CO₂ fluxes; surface diffuse emissions; stable isotopes; hot springs; Planchón-Peteroa volcanic complex.