Fluids Geochemistry from Planchón-Peteroa-Azufre volcanic Complex, Southern Volcanic Zone

SALTORI O.; AGUILERA F,.; AGUSTO M.R.; BENAVENTE O.; TASSI F.; CASELLI A.T.; GUTIERREZ F; PIZARRO D.

Antofagasta

Congreso; XIII Congreso Geológico Chileno; 2012

Peteroa is a composite stratovolcano located at the border between Chile and Argentina (35 º 31'W-70 ° 14'S-4,107 m a.s.l.) and belongs to the Planchon-Peteroa- Azufre Volcanic Complex. Peteroa presents 4 craters hosting acidic lakes and 3 of them with fumarolic activity. Several thermal springs, occasionally associated with bubbling gases, were recognized in the surrounding of the volcano. Gas geochemistry suggests the presence of a shallow hydrothermal system, constituted by vapor separated from a boiling aquifer at temperatures from 275°C to 340°C, which is affected by input of deep magmatic species (e.g. SO2, N2 and 3He). A mix of hydrothermal and meteoric end members characterizes surrounding thermal springs, although magmatic input cannot be ruled out. Crater lakes have acidic SO4 2+ waters, whereas the thermal springs located within the Gendarmería, El Azufre and External valleys, have a HCO3 - -Na+ and Cl--Na+ composition.