Deep-Circulating Salty-Fluids in Cambrils del Pirineu (Pyrenees, NE Iberian)

Salt springs in Cambrils del Pirineu (Pyrenees, NE Iberian Peninsula) are related to diapirism of Triassic (Keuper) evaporite-bearing deposits. Such brines, which are close to NaCl saturation, have been used at least since s. XVIII to produce non-marine table salts. The present research aims to study the hydrogeological system in a high salinity spring water from mountain source in the southern Pyrenees using geochemical study of water and its association with local geology. The research includes total conductivity, major anion and element analyses by means of HPLC and ICP-OES and water flow measurements for one-year period. Sampled waters include a salty spring and nine closer freshwater springs. Conductivity of the salt water is close to 44 mS/cm, chloride is about 17% and Na is close to 10%, with minor amounts of sulphate, K, Ca, Mg and Sr. Water flow is about 4 L/min (July 2021 to June 2022). Minor increase in the flow rate is related to superficial inflows during last metres of brine circulations before outcropping. Freshwater springs have HCO3-Ca compositions but show a slight Mg-SO4 enrichment due to nearby Triassic evaporites. Eh of brine at source is only of 12 mV, thus evidencing its reductive behaviour. Local geology suggests large brine circulation along Triassic-Cretaceous contact until surface discharge. This model differs from previous interpretations, which pointed to more superficial recharge and fluid circulation.