A multi-isotope study of the Castrocaro mineral waters (Northeastern Apennines, Italy).

An applied multi-isotope approach (?2H, ?18O, ?11B, ?13C, ?15N, ?34S), coupled with chemical evidence, allowed us to constrain a conceptual hydrogeological model for the Castrocaro sulfureous groundwater system that is composed of fresh, brackish, and saline components. In this model, the meteoric recharge enters the turbidite sequence of the Marnoso-Arenacea Fm., undergoing chemical and isotopic modifications by interaction with fine grained pelite rocks, mixing with fossil seawater, and biochemical reactions. The groundwater then rises into a biocalcarenite unit, which acts just as a reservoir from which the resource is finally exploited by wells feeding the Castrocaro Terme spa.