Geochemical interpretation of thermal fluid discharge from wells and springs in Berlín geothermal field, El Salvador

Abstract

The Berlín geothermal field is located in a tectonically very active area due to the subduction of the Cocos plate under the Caribbean plate. The chemical composition of waters in the study area is governed by water rock interaction. In this study, the Cl-SO4-HCO3 and Na-K-Mg triangular diagrams and stable isotopes were used to classify the geothermal and cold spring waters and to study some processes in the geothermal system. The geothermal waters are sodium chloride type with a high content of boron and lithium, indicating reactions with basic and acidic volcanic rocks. The cold spring waters are bicarbonate waters and the hot spring waters chloride waters. The calculated quartz and chalcedony geothermometer values for the geothermal well waters indicate reservoir temperatures of 236-264°C, lower than values for cation geothermometers, probably due to the fast reaction rate of silica at high temperature. The Na-K-Ca and N-K geothermometers give mostly higher values for the wells, or 262-304°C. The gas geothermometers applied indicate temperatures of 232-295°C ...