Characterisation of the Khoy geothermal area/NW Iran based on isotope and chemical investigations

The Khoy geothermal system is located in the extreme northwest of Iran, about 30 to 40 km from the Turkish border and about 30 km southwest of the city of Khoy. The main thermal and mineral springs are observed along an approximately 2 km long segment of the north bank of the Qotur Chay (Qotur River). In this Khoy - Qotur thermal area several cold and hot springs are observed. The naturally out flowing highly mineralised waters (electrical conductivity in the range of 3000 to 5000 μS) are of Na-HCO3 type with big excess of CO2 and yield temperatures between 18 and 58 deg. C. The study area is located in a active tectonic area in which different geological formations are set close together. The pressure direction is north south (normal to Qotur valley direction). In this area several horst and graben systems parallel to the valley exist. The Qotur valley itself is filled with clastic sediments. The deep Qotur valley has been formed by a fault. The formation of hot water reservoirs are most probably related to the occurrence of this Qotur fault system. By the interpretation of the analysed samples of the main spring outflows, an artesian borehole and the water of the Qotur river upstream and downstream of the investigated thermal area as also some cold springs of low mineralised water a first characterisation of the hydrogeological features is possible and will be presented in this publication based on isotope analyses of 2H, 18O, 3H, 13C, 14C, and of the results of chemical analyses