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-de grees-C and chloride-rich fluids; and (b) a shallow aquifer, with a ch loride content close to that of sea water and temperatures in the rang e 170-255-degrees-C. The vapor phase boiled from the shallow aquifer f eeds the fumarolic vents in the southern half of the Lakki plain and i ts liquid phase flows northeast and southwest, contributing to the the rmal springs located along the northern and southern coasts of the isl and. This conceptual hydrogeochemical model of Nisyros Island can be u sed to reconstruct past hydrothermal eruptions and to estimate the ris k of such events happening again in the future.