Groundwaters on the island of Salina (Aeolian Archipelago, Italy): geochemical aspects and genetic considerations

The groundwaters of the island of Salina belong to two main, overlying aquifers: a cold, shallow one characterised by mineral waters with a salinity around 2-3 g/l and a deep one with warmish waters whose composition ranges from saltwater to actual seawater. The compositions are similar in terms of their fundamental components, both of the Na-Cl type, linked to supply which is both indirect (cyclic salts, sea spray) and direct (deep marine groundwaters), respectively. The variations, in terms of both chemical characteristics and temperature, in the deep aquifers (in the range 28-38°C) are predominantly linked to variable dilution with cold, phreatic surface waters. Considerations of a geothermometric nature suggest deep temperatures not greater than 50-60°C, while the presence of a modest anomaly in H₃BO₃, HCO₃^- and SO₄^2- could indicate even a minor but significant convective heat supply, carried by hot rising fluids, probably along tectonic lines with a predominantly N-S trend.

Keywords: hydrochemistry; thermal waters; island of Salina; volcanism