Environmental isotopic study of the Campi Flegrei (Naples, Italy) geothermal field

This paper presents the isotopic analyses of water and dissolved sulfate (H, O, T and S isotopes) from several thermal springs emerging from the volcanic cover in the Campi Flegrei area, sampled both in 1971 and 1975. Large chemical and isotopic variations with regard to sampling times have been observed in some manifestations as more negative isotopic contents of the dissolved sulfate and lower chloride and sulfate concentrations correspond to more negative water isotopic values and vice versa. The chemical and sulfate-water isotopic geothermometers in general do not reflect the real situation in the system. Only the spring fed by marine water and unaffected by mixing phenomena shows consistent equilibrium temperatures at depth