The Incapillo Caldera geothermal system: Implications for geothermal resources in the Southern Central Andes, Argentina

Abstract

The Incapillo Caldera, located along the Ojos del Salado–San Buenaventura volcanic lineament (Southern Central Andes) exhibits limited surface geothermal manifestations, yet multiple independent datasets suggest the persistence of a residual hydrothermal system at depth. This study integrates hydrochemical, stable isotope (δ18O–δ2H), mineralogical, structural, and thermal modeling data to evaluate the geothermal potential of this poorly expressed volcanic system. Hydrochemical signatures, particularly from Corona del Inca Lake, indicate the condensation of geothermal gases into surface waters, producing acidic, sulfate-rich compositions. Stable isotope data reveal variable mixing between meteoric and magmatic fluids, especially at the Los Baños thermal springs, where inferred paleotemperatures of up to ∼90 °C suggest sustained hydrothermal circulation. Mineral assemblages, including silica sinter, evaporitic phases, and low-temperature alteration minerals, record progressive cooling and increasing meteoric recharge. Microfossilized microbial communities further provide independent evidence of higher past thermal conditions. Structural analysis highlights the possible role of fault-controlled permeability along the Ojos del Salado–San Buenaventura volcanic lineament, which may provide pathways for fluid circulation in a blind geothermal system. Thermal modeling suggests the persistence of residual magmatic heat associated with the most recent eruptive episode, capable of sustaining long-lived hydrothermal activity. Although current surface temperatures are moderate, the integrated dataset indicates that the Incapillo Caldera remains thermally and tectonically non-inert, warranting further multidisciplinary exploration.