CO2-rich thermomineral groundwater in the Betic Cordilleras, southeastern Spain: Genesis and tectonic implications

The CO2-rich thermal groundwater in the Betic Cordilleras in Spain has been studied with regard to the geological and hydrogeological setting, physica l and chemical characteristics, and C-13-isotope content. The study area is about 60 km northeast of Almeria city, in southeastern Spain. The thermomi neral waters are plentiful and are related to regional geothermal anomalies . Temperatures of 20-41 degrees C, high bicarbonate concentrations (183-182 4 mg/L), and high amounts of PCO2 (< 1.1 bar) characterize the groundwater. CO2 spatial variations are related to proximity to the Carboneras, Palomar es, and Guadalentin fault systems, which may be the surface representation of the zone of crustal thinning and magmatism. delta(13)C values probably i ndicate a deep source for the CO2, either the mantle or perhaps carbonate r ocks in the metamorphic substratum. The high amount of CO2 in the groundwat er causes problems in wells and severely restricts water usage. The hydroth ermal features of this area are probably related to neotectonic activity.