Geothermal potential of karacasu (Aydin) province

The study area is around Karacasu, located approximately 70 km southeast of Aydın province. The study aims to determine the geothermal potential of the region, the hydrochemical properties of the hot waters in the area, and their origin, as well as to identify the recharge areas. There are five formations in the area, consisting of bedrock, Dandales, Karacaören, and Karacasu Formations, and alluvium. Ten samples were taken from hot water wells, cold water wells, and springs in the study area. The temperature of the cold waters is 18-19 °C, pH is 7.9, EC values are 450-470 µS/cm, TDS value is 200-230 ppm, the temperature of the hot waters is 24-29 °C, pH is 8, EC values are 510-1100 µS/cm, and TDS is between 250-270 ppm. The springs and boreholes around Karacasu are located within the lithology of coarse-grained alluvial fans, with aquifer thickness exceeding 180 meters, extending down to lagoonal facies and lacustrine deposits. In the Schoeller diagram, the lines connecting the ions are approximately parallel and are of the same origin in the Ca, Mg, HCO3 facies. Hot water sources have similar feeding and reservoir rock types. The reservoir rock temperature is 160-430 oC, and the cold water mixing ratio is 85-98%. Rainwater that filters down to the bedrock and collects in permeable units filters deep into the ground and heats up due to the high geothermal gradient there. The heated water rises along faults and fracture systems, mixing with colder groundwater at shallower depths and cooling conductively as it ascends toward the surface. The hot and cold waters in the study area, except for the Yeşilköy spring, Yeşilköy fountain, and Geyre borehole, are saturated with aragonite, calcite, and dolomite minerals and have precipitating properties. All waters are not saturated with anhydrite, gypsum, halite, and sylvite minerals and have dissolving properties. According to Giggenbach's (1988) diagram, the hot waters in the study area remain in the immature raw water zone. The geological, hydrogeological, and hydrogeochemical characteristics of the Karacasu graben are suitable for geothermal potential. Within the BMG, numerous geothermal wells have been drilled around the Karacasu graben, and several geothermal power plants have been in operation for a long time