Chemical and isotopic characterization of the thermal fuids emerging along the North-Northeastern Greece

Hydrochemical and isotopic characteristics of fuids from major geothermal felds of middle/low temperature in N/NE Greece are examined [basins: Strymon River (SR), Nestos River Delta (ND), Xanthi-Komotini (XK), Loutros-Feres-Soufi (LFS) and Rhodope Massif]. The geodynamic context is refected to isotopic/chemical composition of fuids, heat fow values and elevated CO2 concentrations in emitted fuids. B and Li are derived from leaching of the geothermal systems hosting rocks. delta18OH2O, delta18OSO4, delta13CCO2 values and chemical compositions of Cl, B and Li of geothermal discharges suggest two distinct source fuids. Fluids in SR exhibit high B/Cl and Li/Cl ratios, suggesting these constituents are derived from associated magmas of intermediate composition (andesitic rocks). Geothermal discharges in LFS exhibit low B/Cl and Li/Cl ratios, implying acid (rhyolitic) magmatism. delta13CCO2 and CO2/(CO2 + ¬105 He) ratios in the west part, suggest fuids afected by addition of volatiles released from subducted marine sediments. For the eastern systems, these ratios suggest gas encountered in systems issued from mixing of crustal and mantle-derived volatiles. Isotopic geothermometers refect, for the same direction, equilibrium processes more (LFS, XK) or less (SR) pronounced and discriminate the geothermal feld from low to middle [SR, ND (Erasmio)] and middle to high enthalpy [ND (Eratino), LFS, XK].