Temperature estimation of the Nevado del Ruiz Volcano geothermal reservoir: Insight from western hot springs hydrogeochemistry

Geochemical surveying is one of the techniques of geothermal exploration that include geothermometry to estimate the temperature of deep reservoirs. This work provides the temperature estimation of geothermal resources, geochemical analysis, and a conceptual model of the geothermal reservoir located to the western flank of the Nevado del Ruiz Volcano (NRV), a mayor geothermal target for energy production in Colombia. Hydrogeochemical data (pH, temperature, electrical conductivity, major, minor, and trace elements) were obtained from water samples collected at several hot springs located to the west of the NRV between 2017 and 2019. The data available from the Colombian Geological Survey database were also included in the analysis to better characterize the hot spring behavior. The hydrogeochemical tools Liquid analysis Powell and Cumming and GQAnalyzer software were used to draw ternary diagrams and to use geothermometers. The results allowed separating the hot springs into two groups, according with their chemical characteristics and spatial location: Nereidas 1, Nereidas 2, Nereidas Pozo, and Chorro Negro hot springs belong to Group 1 (G1), located closer to the NRV; on the other hand, Geysers, El Bosque-La Piscina, Quebrada Negra, and Rio Claro, which are located further from NRV, belong to Group 2 (G2). The latter is made of mature and chloride waters, indicating a water-rock equilibrated interaction with most of ions. The results of this study contribute to the future Colombian geothermal development, and the methodology and analysis can be applied to geothermal systems with similar geological characteristics to infer a conceptual model useful for geothermal exploration.