Identification of a Potential Geothermal Resource at Aguas de Vichy Hot Springs, Colombia, Through Integrating Geoelectrical and Electromagnetic methods

The Aguas de Vichy thermal spring, identified by the Colombian Geological Service (SGC) and located in Santander, Colombia, represents a significant but underexplored geothermal resource. This study presents the first geophysical imaging of the system, integrating Electrical Resistivity Tomography (ERT), Induced Polarization (IP), and Time-Domain Electromagnetics (TDEM) to characterize its structure. Existing geochemical analyses reveal high salinity and elevated temperatures, indicative of energy potential and an advection-dominated thermal regime. The geological context is marked by north–south and northeast–southwest fault systems intersecting Cretaceous and Precambrian rocks, overlain by a Quaternary aquifer. Four ERT profiles and two TDEM soundings were acquired to characterize the geothermal system at Aguas de Vichy. ERT 1 and 2, crossing the main fault, revealed strong lateral resistivity contrasts (near 0 to > 1500 Ω·m) associated with clays, groundwater, and thermal anomalies, while the third ERT, located away from the fault, showed a predominantly resistive background suggesting limited geothermal influence. Complementary TDEM soundings extended the investigation to ~100m depth, identifying a low-resistivity anomaly interpreted as a geothermal reservoir and suggesting a fault-aligned hot-water plume feeding the aquifer. These findings support a convective flow driven by vertical fluid ascent along the fault zone in addition to the previous advection-based hypothesis. The integrated geophysical dataset highlights the complexity and geothermal potential of the system, providing critical insights for future exploration and contributing to Colombia’s energy transition roadmap.