Contributions for the Understanding of the São Pedro do Sul (North of Portugal) Geohydraulic and Thermomineral System: Hydrochemistry and Stable Isotopes Studies

São Pedro do Sul thermomineral aquifer system is located in the North of Portugal. Hydrogeochemistry and isotopic studies were conducted in order to improve knowledge of this groundwater system, known since ancient Roman times for their therapeutic properties. One thermomineral spring (NT) and three boreholes (AC1, SDV1 and SDV2) have a mean temperature around 68 °C. Currently, these waters are mainly used in thermal spas and for geothermal energy supply. Major cations and anions were used to identify and characterize different water types and sub-systems. Stable isotopes composition, δ18O and δ2H, have been used to determine the origin and have been used as a first approach to estimate the mean preferential recharge altitude of thermomineral water. The results suggest a single aquifer system with a relative composition of cations and anions and similar mineralization values. δ18O and δ2H values indicate a meteoric origin with no significant evaporation before infiltration. Besides, the isotopic composition points to recharge areas located at altitudes of about 1000 m a.s.l. This suggests a recharge area in the Freita/Arada mountains located NW of the thermomineral poles.

[1]  Chenhua Li,et al.  Hydrogeochemical Characteristics of Hot Springs and Their Short-Term Seismic Precursor Anomalies along the Xiaojiang Fault Zone, Southeast Tibet Plateau , 2021, Water.

[2]  C. Cardellini,et al.  The Role of Faults in Groundwater Circulation before and after Seismic Events: Insights from Tracers, Water Isotopes and Geochemistry , 2021, Water.

[3]  M. Barbieri,et al.  Understanding the Origin and Mixing of Deep Fluids in Shallow Aquifers and Possible Implications for Crustal Deformation Studies: San Vittorino Plain, Central Apennines , 2021, Applied Sciences.

[4]  D. Newell,et al.  Structural Controls on Crustal Fluid Circulation and Hot Spring Geochemistry Above a Flat‐Slab Subduction Zone, Peru , 2020, Geochemistry, Geophysics, Geosystems.

[5]  Harun Aydin,et al.  Hydrogeochemistry of geothermal waters in eastern Turkey: Geochemical and isotopic constraints on water-rock interaction , 2020 .

[6]  J. Paredes,et al.  Hydrogeochemistry, isotopes and geothermometry of Ixtapan de la Sal–Tonatico hot springs, Mexico , 2019, Environmental Earth Sciences.

[7]  E. Dotsika,et al.  Chemical, isotopic and geotectonic relations of the warm and cold waters of the Galatro and Antonimina thermal areas, southern Calabria, Italy , 2019, Marine and Petroleum Geology.

[8]  P. Carreira,et al.  Revision of the hydrogeological conceptual models of two Portuguese thermomineral water systems: similarities and differences , 2019, Sustainable Water Resources Management.

[9]  G. Courrioux,et al.  Topographic and Faults Control of Hydrothermal Circulation Along Dormant Faults in an Orogen , 2018, Geochemistry, Geophysics, Geosystems.

[10]  A. Trota,et al.  Reservoir Considerations and Direct Uses of São Pedro do Sul Hydromineral and Geothermal Field, Northern Portugal , 2017 .

[11]  I. Matiatos,et al.  USE OF STABLE ISOTOPES IN THE DETERMINATION OF THE MEAN ALTITUDE OF RECHARGE AND THE INVESTIGATION OF FUNCTION MECHANISM OF SPRING WATERS IN ARGOLIS PENINSULA (GREECE) , 2017 .

[12]  P. Koeniger,et al.  Stable isotopes of precipitation and spring waters reveal an altitude effect in the Anti‐Lebanon Mountains, Syria , 2016 .

[13]  J. Cruz,et al.  Using stable isotopes to characterize groundwater recharge sources in the volcanic island of Madeira, Portugal , 2016 .

[14]  H. Chaminé,et al.  Assessment of mixing between shallow and thermal waters using geochemical and environmental isotope tracers (N Portugal): a review and reinterpretation , 2014, Environmental Earth Sciences.

[15]  P. Carreira,et al.  Carbon isotopes and geochemical processes in CO2-rich cold mineral water, N-Portugal , 2014, Environmental Earth Sciences.

[16]  L. Araguás‐Araguás,et al.  Isotopic Patterns in Modern Global Precipitation , 2013 .

[17]  M. Morais.  Sistemas hidrominerais nos terrenos graníticos da Zona Centro-Ibérica em Portugal Central : perspectivas químicas, isotópicas e genéticas sobre as águas sulfúreas , 2013 .

[18]  B. Mayer,et al.  Isotopic and hydrochemical data as indicators of recharge areas, flow paths and water-rock interaction in the Caldas da Rainha-Quinta das Janelas thermomineral carbonate rock aquifer (Central Portugal) , 2013 .

[19]  J. Carvalho,et al.  Defining the dynamics of groundwater in Serra da Estrela Mountain area, central Portugal: an isotopic and hydrogeochemical approach , 2011 .

[20]  P. Carreira,et al.  Hydrothermal alteration of Hercynian granites, its significance to the evolution of geothermal systems in granitic rocks , 2010 .

[21]  P. Carreira,et al.  A 15-year record of seasonal variation in the isotopic composition of precipitation water over continental Portugal , 2009 .

[22]  A. Ord,et al.  Faulting and fluid flow in porous rocks and sediments: implications for mineralisation and other processes , 2009 .

[23]  R. Large,et al.  Factors controlling free thermal convection in faults in sedimentary basins: implications for the formation of zinc–lead mineral deposits , 2004 .

[24]  J. Fontes,et al.  The altitude effect on the isotopic composition of tropical rains , 2001 .

[25]  L. F. Gomes,et al.  Protection areas of the São Pedro do Sul Spa, Portugal , 2001 .

[26]  L. Araguás‐Araguás,et al.  Deuterium and oxygen‐18 isotope composition of precipitation and atmospheric moisture , 2000 .

[27]  James P. Evans,et al.  Fault zone architecture and permeability structure , 1996 .

[28]  K. Różański,et al.  Relation Between Long-Term Trends of Oxygen-18 Isotope Composition of Precipitation and Climate , 1992, Science.

[29]  W. Giggenbach.  Geothermal solute equilibria. Derivation of Na-K-Mg-Ca geoindicators , 1988 .

[30]  M. Schoonen,et al.  Geochemical studies in the drainage basin of the Rio Vouga (Portugal): II. A model for the origin of hydrothermal water in the Vouzela region , 1985 .

[31]  D. B. Clarke.  The mineralogy of peraluminous granites; a review , 1981 .

[32]  H. Craig.  Isotopic Variations in Meteoric Waters , 1961, Science.

[33]  Arthur M. Piper,et al.  A graphic procedure in the geochemical interpretation of water-analyses , 1944 .

[34]  P. Carreira,et al.  Recharge Conceptual Model and Mineralization of Groundwater in a Semi-arid Region; Essaouira Basin (Morocco) , 2017 .

[35]  P. Carreira,et al.  Preliminary Geochemical and Isotopic Results in Thermal and Cold Waters of Graciosa Volcanic Island (Azores) , 2017 .

[36]  I. Clark.  Stable Isotope Geochemistry , 2011 .

[37]  Mark A. Knackstedt,et al.  Principles of Structural Control on Permeability and Fluid Flow in Hydrothermal Systems , 2001 .

[38]  P. Domenico,et al.  Physical and chemical hydrogeology , 1990 .