Geoquímica de las aguas termales con CO2 del SE de las Cordilleras Béticas

Abstract

The hydrothermalism of the south-east peninsular Alpine zone has been studied under different points of view, such as the geological control, the definition and systematising of its chemistry types and base temperatures, among others, showing always its notable development and its connection with geothermal anomalies of regional character. One of the problems that seems to carry important genetic implications, as well as implications for the utilisation of this water, is the content in carbon dioxide. Twenty-seven physicalchemical parameters in twenty-two water points on a fifty inventory have been studied. High temperatures were recorded for almost all the sampling points, varying between 20 and 41°C. The waters have conductivity between 771 and 5,030 μS cm^-1 and increased to the east of the faults systems of Carboneras-Palomares-Guadalentín. In general, the concentration in bicarbonate was high, between 3 and 30 meq/l. The waters present high PC0₂, being arrived to measure values over 1.17 atmospheres and whose spatial variations are related to the proximity to the faults systems of Carboneras-Palomares-Guadalentín, the one which establishes a threshold between different thickness of the crust. Chemical equilibrium modelling shows that the waters are oversaturated in dolomite, in general saturated in calcite, and undersaturated in gypsum. The high content in CO₂, besides the process of dedolomititation caused by the addition of S04~ to the system, helps the formation of travertines in many of the studied points. Isotopic studies show that δ¹³C values are in the range -S.I to -3.1‰, and reveals that there is an insignificant CO₂ supply of deep origin The hydrothermal system of this zone is related to the proposed «C0₂ Alpine Belt», associated here with a series of grabens with seismic and neotectonic activities.