SOIL CO2 FLUX AND TEMPERATURE FROM A NEW GEOTHERMAL AREA IN THE CORDÓN DE INACALIRI VOLCANIC COMPLEX (NORTHERN CHILE)

This paper deals with the first geochemical data from an unexplored sector of the Cordon ´ de Inacaliri VolcanicComplex (Central Andes, Chile). The site is located at ~5,150-5,200 m a.s.l., inside the Pabelloncito grabenwhere, at about 9 km NW of the studied area, the only currently working geothermal power plant of SouthAmerica, named Cerro Pabellon, ´ occurs. Diffuse soil CO2 and soil temperature measurements were carried out tounravel the structural control on the rising fluids and estimate the total CO2 output, the heat flow rate and theheat flux, aimed at assessing a preliminary evaluation of the geothermal potential of the area. The study area ischaracterized by a pervasive hydrothermal mineralogical alteration, CO2 flux values of up to ~4,400 g m-2 d-1and soil temperatures up to the boiling point of water at that altitude. All these features are likely related to anendogenous source. Spatial distribution of both soil CO2 flux and temperature depict an ENE-striking lineament,whose intersection with the NW-striking Pabelloncito graben forms a favourable structural setting for thedischarge of hydrothermal fluids. The total CO2 output emission of the studied area (~0.0179 km2) was ~0.53 td-1, with an associated discharge of steam of 6.45 t d-1 (CO2/H2O ratio = 0.08). An electric capacity potential of1.08 MWe km-2 was computed from the heat flow rate and heat flux values. Our results suggest that this part ofthe Pabelloncito graben is an interesting geothermal prospect and a good candidate for further explorationstudies.