Las aguas termales de Fitero (Navarra) y Arnedillo (Rioja). II. Análisis comparativo de la aplicación de técnicas geotermométricas químicas a aguas relacionadas con reservorios carbonatado-evaporíticos

Abstract

We have checked the geothermometrical technics for Fitero and Amedillo thermal waters. Both of them belong to low enthalpy systems and are associated to carbonatic-evaporitic reservoirs, where the basic asumption of equilibrium for most geothermometers is doubtful. So, Na-K, Na-K-Ca and Na-K-Ca-Mg geothermometers can't be applied because of their supposed equilibrium fails at depth. Some calibrates appear to be in good agreement with other geothermometers (e.g. silica-quartz) but this can be explained by an unsuitable relation between their basic equilibrium assumption and the waters used for calibrate them. The specific geothermometers calcite-dolomite and anhydrite-fluorite (Marini et al., 1986) developped for carbonatic-evaporitic environments are very influenced by reequilibration processes such as mixture phenomena and water-rock reactions during the rising of waters, and they must be handled with care. The good agreement between silica-quartz, K-Mg and Na-Li geothermomethers suggest the existence of a possible equilibrium between argillaceous minerals at depth.