Soil gas flux, hydrogeochemistry and multicomponent geothermometry of thermal springs in the La Escalera geothermal prospect, Mexico

Abstract

The La Escalera geothermal system, a southern region of the Sierra Mil Cumbres, Mexico, is considered a potential prospect for geothermal resources. Geochemical exploration techniques such as thermal water chemical analysis, soil gas flux measurements, mineralogy analysis, and geochemical modeling were applied to develop a conceptual model of the geothermal area. Thermal water samples were analyzed to examine their chemical features. The thermal waters are mainly near-neutral bicarbonate type with sodium as the major cation. A high variation of gas fluxes was observed, and the correlation of CO2 diffuse degassing with fault system in the La Escalera geothermal area is related to local failure stresses. The integrated multicomponent geothermometry method was performed to rebuild deep fluid chemical composition and estimate the optimal bottom temperature. Results show a bottom temperature of 120 °C where concentrations of Al, Mg, CO2, and selected minerals for geothermometry modeling are critical variables for successfully constraining the mixing processes. Geochemical modeling was performed to evaluate the water-rock equilibria. The chemical characteristics of the thermal waters indicate interaction with andesitic rocks, and the chemical processes governing the formed hydrothermal mineralogy include both cation exchange and hydrolysis reactions. The methodology of this study can be helpful for other potential geothermal areas with similar conditions.