Isotope and chemical assessment of geothermal potential of Kos Island, Greece

The island of Kos is located in the southern part of the Aegean volcanic arc[ Between 0880 and 0882\ water and gas samples were collected from cold and thermal springs and from several water drill!holes[ The maximum surface temperature of 34>C is associated with Fokas spring water\ which consists of a seawater modi_ed by interaction with sedimentary rocks in the NW part of the island[ Two distinct groundwater circulations develop in the sedimentary and volcanic rocks^ these are meteoric waters dominated by HCO2 ions that have ions formed by interaction with the calcite present in the rocks as primary or secondary mineral[ Addition of CO1 from an external source to the groundwaters locally leads to the formation of aggressive waters and a water rock interaction characterised by the leaching of CaSO3 and partial attain! ment of mineral:~uid equilibrium[ The gas compositions suggest the presence\ at depth\ of a CO1!producing high!temperature system in its waning stage[ On the basis of chemical solute geothermometry\ temperatures higher than 009>C appear unlikely at relatively shallow depths[ 0888 CNR[ Published by Elsevier Science Ltd[ All rights reserved