Fluid geochemistry of Nisyros island, Dodecanese, Greece

Two distinct hydrothermal aquifers are present beneath the Lakki plain: (a) a deep aquifer, characterized by temperatures higher than 290°C and chloride-rich fluids: and (b) a shallow aquifer, with a chloride content close to that of sea water and temperatures in the range 170–255°C. The vapor phase boiled from the shallow aquifer feeds the fumarolic vents in the southern half of the Lakki plain and its liquid phase flows northeast and southwest, contributing to the thermal springs located along the northern and southern coasts of the island. This conceptual hydrogeochemical model of Nisyros Island can be used to reconstruct past hydrothermal eruptions and to estimate the risk of such events happening again in the future.