| Abstract |
Varto, in the eastern part of Turkey, is settled around the conjunction point of the East Anatolian (EAF) and North Anatolian (NAF) Fault zones. The border of these tectonic zones constitutes seismic belts marked by young volcanic associations and active faults, the latter allowing circulation of waters as well as heat. For this reason, there are various geothermal systems having several hot water springs in the region. The distribution of hot water springs in the Varto Region roughly parallels the distribution of the fault systems and young volcanism. Samples from five hot water and two mineral water springs together with cold (peripheral) waters were collected. Hot water samples were assessed through geothermometers in terms of geothermal usage opportunities. All water samples were measured and analyzed for physical, chemical and isotopic compositions. Physical parameters such as pH, electrical conductivity (EC; µS/cm) and temperature (T; ºC) were measured in field. Primary (major ions) and secondary constituents (trace elements and heavy metals) and Oxygen 18 (18O), Deuterium (D), Tritium (3H) isotopic compositions were determined by mass spectrometry. Average discharges of hot water springs in the study area are between 1 - 5 L/sec. Surface temperatures of these springs vary 22.5 to 32ºC, electrical conductivity (EC) values 2100 to 5775µS/cm. Average discharges of mineral waters in that site are between 0.5 - 2 L/sec. Surface temperatures of them were measured as 13.2 and 14.8ºC. Their electrical conductivity values are also in the range of 719 - 751 µS/cm. The average discharges of cold water springs in the study area are between 1 - 150 L/sec. Surface temperatures of these springs change between 4.9 - 11.7ºC and electrical conductivity values 51 - 199 µS/cm. Regarding pH values, water samples belonging to the site are entirely distinguished into the pH range of ~5.4 - ~6.2 for hot and mineral waters, ~6.2 - ~7.7 for cold waters. Hot water springs have acidic character, whereas pH values of cold water springs change from slightly acidic to neutral and slightly basic. In the vicinity of the study area, volcanic and volcaniclastic rocks crop out. Groundwater flow in the volcanic rocks is also controlled by the presence of structural features as suggested by the alignment of the springs. Their cooling fractures extend several meters in depth, providing a good avenue for deep penetration and circulation of groundwater. According to the Piper diagram, springs fall into Na-HCO3-Cl type for thermal waters and Ca-HCO3 type for cold waters. Due to the fractures allowing deep circulation of groundwater and dominant Na-Cl component, the host rock is probably volcanic origin. Hot waters have the same recharge area with cold waters. The information on the fluid origin and the age of springs depicted by their 18O-D and T contents shows that they are all meteoric origin and hot water springs are older than 50 years. Reliable reservoir temperature ranges for hot waters were obtained with Li-Mg geothermometer and β-Cristobalite geothermometer as 44 - 66ºC and 54 - 80ºC, respectively. These values are also checked with Saturation Indices (SI) vs T diagrams. Results of SI vs T diagrams point out equilibration with calcite and aragonite minerals which gives comparable results with Li-Mg and β-Cristobalite geothermometers. It is possible to get 80°C reservoir temperature by drilling in this area with the help of field observations and the data obtained. The geothermal potential of the study area have not been used up to now. This geothermal district might make a considerable contribution to tourism and agriculture usages. |