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HYDROTHERMAL SYSTEMS (NW-PORTUGAL): A GEOCHEMICAL AND ISOTOPIC ASSESSMENT

 

rei3Bica Spring – Gerês thermomineral system. RIGHT Schematic representation of the conceptual circulation model of Gerês thermomineral groundwater system (adapted from Guerra, 2015).A comparative study based on geochemical and environmental isotope data was conducted in three low-temperature aquifer systems located in the north of Portugal (Monção, Caldelas and Gerês hydrothermal systems), in order to demonstrate the role of combined hydrogeological tools to improve knowledge on the conceptual circulation models. Environmental isotopes (2H and 18O) were used as natural tracers to estimate the origin and altitude of the recharge areas of these thermomineral aquifer systems, and in the characterization of groundwater flowpaths. The tritium (3H) content was used in issues related to the dynamics of the groundwater flow systems and identification of mixing processes between different aquifer units. Carbon isotopes, 13C and 14C, allowed the determination of the main sources of the total carbon dissolved in the aqueous system and estimation of the apparent groundwater age of these thermomineral groundwater aquifers. Based in this information conceptual circulation models were proposed: 1. recharge areas located at higher elevations; 2. the meteoric waters infiltrates at depth through major fractures and faults in the granitic massive; 3. water-rock interaction is enhanced, and therefore the TDS in water increases, being temperature dependent.

 

 


Contact persons:

Paula Carreira ()

Dina André ()

 

References:

Carreira, P.M.; Marques, J.M.; Carvalho, M.R.; Nunes, D.; Antunes da Silva, M. (2014) - Carbon isotopes and geochemical processes in CO2-rich cold mineral water, N-Portugal. Environmental Earth Sciences, 71: 2941-2953. DOI 10.1007/s12665-013-2671-x

Marques, J.M.; Matos, C.; Carreira, P.M.; Espinha Marques, J.; Teixeira, J.; Chaminé, H.I. (2014) – Assessment of mixing between shallow and thermal waters using geochemical and environmental isotope tracers (N Portugal): a review and reinterpretation Environmental Earth Sciences,72: 2557-2567. DOI:10.1007/s12665-014-3162-4.

Carreira, P.M.; Carvalho, M.R.; Nunes, J.C.; Grassa, F.; Capasso, G.; Marques,  J.M. (2017) - Preliminary geochemical and isotopic results in thermal and cold waters of Graciosa volcanic Island (Azores). Procedia Earth and Planetary Science 17: 630-633. doi: 10.1016/j.proeps.2016.12.169

Marques, J.M.; Carreira, P.M. (2017) - Questions and answers ascribed to Chaves CO2-rich thermal waters conceptual model (N Portugal): a review. Procedia Earth and Planetary Science 17: 654-657. doi: 10.1016/j.proeps.2016.12.175