Geochemical characterization of groundwaters from the Hyblean aquifers, South-Eastern Sicily

摘要

Groundwaters hosted within unconfined aquifers were collected from sixty-five cold and slightly thermal springs and wells. The studied aquifers are mainly constituted of a thick sequence of carbonates, Meso-Cenozoic in age. Basic volcanic intercalations, occurring during several episodes, are also present. Except for the samples located near the coast where seawater contribution plays an important role, the chemical composition of studied groundwaters is controlled by water-rock interaction. The proposed geochemical mass balance model suggests that Ca+Mg/HCO_3 groundwaters evolve toward a Na-HCO_3 type due to interaction with volcanic rocks, thus forming secondary minerals. pCO_2 values up to 0.1 atm suggest a contribution of a CO_2-gas source. The 5~(13)C_(TDIC) values range between -15 to -8 per thousand vs PDB, indicating mixed organic-inorganic carbon sources.