Isotopic identification of CO2 from a deep origin in thermomineral waters of southeastern Spain

Abstract

The overexploitation of the Alto Guadalentín detrital aquifer has led to an unusually high gas content in the waters, which is released as the hydrostatic charge decreases. The predominant gas proved to be CO . Isotopic studies show that d182 O values are in the range y8.8 to y6.5‰ SMOW, d D ranges between y45 and y40‰ SMOW, excess deuterium lies between q8.0 and q27.4, and d13C values lie between y8.1 and y3.8‰ PDB. This reveals that there is an enrichment in 18O as well as mixing processes between meteoric and deep circulating waters. Tectonic and seismotectonic studies indicate crustal thinning in the studied region and numerous normal, reverse and strike-slip faults marked by positive thermal anomalies. There is also evidence of present day tectonic activity.