Hydrogeochemical Investigation of Geothermal Springs in Erzurum, East Anatolia (Turkey)

Environmental Earth Sciences (2018) 77:802 https://doi.org/10.1007/s12665-018-7986-1 ORIGINAL ARTICLE Hydrogeochemical investigation of geothermal springs in Erzurum, East Anatolia (Turkey) Mine Alacali1 Received: 2 May 2018 / Accepted: 3 December 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Geothermal water sources located within The Erzurum province were identified and hot water samples were taken from four different geothermal areas. The results of in situ and hydrogeochemical analyses of these hot water samples were interpreted and the properties of hot water, water–rock associations, estimated reservoir temperature and hot water usage areas were determined. The temperatures of the samples collected from the study area vary between 26.2 and 57.7 °C, while pH values change from 6.09 to 7.33, EC values obtained from in situ measurements are between 1829 and 9480 µS/cm and Eh values are (− 190) to (26.3) mV. Total dissolved solids of the hot waters have a range from 838.7 to 3914.1 mg/l. The maximum estimated reservoir temperature is calculated as 250 °C by applying chemical geothermometers. However, considering the actual temperatures of Pasinler, Köprüköy, Horasan and Ilıca thermal waters and wells, the most reliable temperature range depending on the applied geothermometers’ results indicate minimum and maximum reservoir temperatures 85–158.9 °C, respectively, taking in account the errors. According to the isotope analysis, the waters circulating within the geothermal system are of meteoric origin and modern waters. In addition, two samples taken from clayey levels observed in the field were analyzed and the mineralogy of the clays was evaluated. Keywords Geothermal · Erzurum · Geochemistry · Geothermometer Introduction identified. These provinces are recorded as Aegean, Ankara, Kayseri, Amanos, Erzurum and Diyarbakır (Erentöz and The Anatolian Plate is geologically active, thus Turkey Ternek 1969). has a great potential in geothermal energy. Erzurum City, In the Erzurum Province, there are 12 known hot water where the investigated springs occur, is located on the points within the boundary of Erzurum City. These are eastern region of Turkey (Fig. 1). Geothermal systems of Uzunahmet, Pasinler, Pasinler–Asboğa, Köprüköy, Ilıca, high temperature waters are mostly located along the gra- Dumlu–Akdağ, Tekman–Gökoğlan, Tekman–Meman, Tek- bens of western Turkey due to the active tectonics. Most man–Hamzan, Horasan–Çermik (Gökçeköy), Çat-Hölenk of the geothermal fields are liquid-dominated geothermal and Olur geothermal fields. Most of the geothermal explo- systems; thus, these geothermal areas are studied intensely ration studies in this region have been carried out by MTA. by many researchers (Akan 2002; Şimşek 2003; Köse 2005, Geothermal energy is one of the alternative energy 2007; Karamanderesi and Ölçenoğlu 2005; Alacalı 2006, sources among the renewable and sustainable energies, 2013; Tarcan et al. 2009; Magri et al. 2010). Geothermal which consumers can benefit by using in space heating, researches in Turkey were initiated by the General Direc- balneological purposes, greenhouse heating and electricity torate of Mineral Research and Exploration (MTA) in Tur- generation. To decide the consumption type of geothermal key in the 1960s and six geothermal energy provinces were water, one needs to know the hydrogeochemical charac- teristics of these resources such as temperature, pH, and major ion and cation values, total dissolved solids (TDS) * Mine Alacali [email protected]; [email protected] and temperature of the reservoir. Within this paper, Pasinler, Köprüköy, Horasan and Ilıca geothermal fields have been 1 Department of Petroleum and Natural Gas Engineering, studied to have an understanding of the geothermal waters Atatürk University, Faculty of Earth Sciences, Erzurum, located in the region. Turkey Vol.:(0123456789)1 3 802 Page 2 of 13 Environmental Earth Sciences (2018) 77:802 Materials and methods the equations of: D/H (SMOW) = 1.050 D/H (NBS-1) and 18O/16O (SMOW) = 1.008 18O/18O (NBS-1), where NBS-1 Within the scope of the study, detailed field studies were is the standard used in the National Bureau of Standards in carried out taking into account the geological maps, geo- America. Negative values characterizing the water sample logical reports and studies formerly recorded for the area. refer to isotopic depletion and positive values refer to the The water samples taken from the determined points were isotopic enrichment with regard to the standard (IAEA examined by means of hydrogeochemistry and the results 1981). were evaluated. During the field studies, four samples from four different geothermal fields have been collected on 2 July, 2014. In situ, hydrogeochemical and isotope Geological setting chemistry analyses were applied to the collected samples. Temperatures (T), hydrogen ion concentrations (pH), The investigated area is located in the eastern part of the redox potential (Eh) and electrical conductivity (EC) were belt, which is defined as Pontides by Ketin (1966). Şaroğlu obtained using WTW Cond 330i and 340i field kit, and the and Yilmaz (1986) reported in their studies titled “Geologi- amount of dissolved oxygen in the liquid (O2) was meas- cal Evolution and Basin Modeling in the Neotectonic Period ured using an oximeter (WTW Oxi340). Total dissolved in Eastern Anatolia” that folds, strike-slip, strike-slip faults solids (TDS) were determined by the in situ analyses of and widening cracks developed during the Neotectonic the samples whose location coordinates were measured. period in Eastern Anatolia that is characterized by compres- The collected samples were stored in 100 ml polypropyl- sion tectonic regime. Under the control of these, two types ene bottles. The water samples were acidified by adding of basins were formed in between the intermontane and the HNO3 (%0.2) to ensure pH < 2, for preserving the cation pull-apart, and they stated that Erzurum–Pasinler–Horasan concentrations of the waters on transfer to the labora- basin is a kind of intermontane basin where the strike-slip tory. The collected samples were analyzed to determine faults are also effective. the major ions, δ18O, δ2H and tritium values. For cations The prevailing tectonic lines in the study area match 2+ 2+ + + 2+ 2+ 2+ 2+ 2+ 4+ (Ca , Mg , Na , K , Fe , Pb , Zn , Cu , Al , Si , with the general direction of the Tauride tectonic assem- 2+ 2+ 2+ + Sr , Ba , Mn , Li ) optic emission spectrometer, for blage in the east–west (Gedik 1985). The study area located − 2− − − + 2− anions (Cl , SO4 , NO3 , NO2 , NH4 , PO4 ) spectro- in Eastern Anatolia is under the influence of compression − 2− photometric method, for ions HCO3 and CO3 titrimet- tectonics and strike-slip faults are observed consequently. ric analyses methods were used. The isotopes of δ2H and The directions of the faults are generally in the NE–SW and δ18O were analyzed using mass spectrometer and 3H was ESE–WNW directions (Boynukalın and Tokgöz 1985). In analyzed using liquid scintillation counting method. These the area where Pasinler, Köprüköy, Horasan and Ilıca hot analyses’ results have been subjected to AquaChem (Calm- water springs are located on a fault line, the oldest unit dis- bach 1997) computer program in order to determine the tinguished is Jura aged sandstone, conglomerate, limestone hydrogeochemical features of the waters. Chemical geo- and claystone (Anonymous 1989). Jura–Cretaceous aged thermometers were applied to the samples to estimate the breccia, sandstone and limestone overlie this unit. A unit reservoir temperature. Silica geothermometers (Fournier comprising serpentine and limestone of the Upper Creta- 1977) and quartz geothermometers (Arnorsson et al. 1983) ceous, limestone and marl of Eocene, gypsum, sandstone were used for the water samples. Also, SolGeo computer and limestone of Miocene is observed in the upper parts program was used to estimate the reservoir temperatures. (Arpat 1965; Anonymous 1989). This sequence is covered SolGeo is a computer program for solute geothermom- by volcanic rocks and lacustrine sediments of Pliocene. The eters which calculates the reservoir temperatures and rep- dominant rocks are basalt and andesite flows. The Gelinkaya resents the results with error estimations, resulting from formation comprising lacustrine sediments overlies the vol- the calculations, measurements (Verma et al. 2008) and canic unit. On the top, a thick aged sequence and Quaternary sampling (Pandarinath 2011). Major anion and cation aged alluvial fans, talus, debris cone and travertines occur. analyses of the water samples were carried out at the Following the closure of the southern part of the Neotethyan JEOSER Earth Sciences Services, Isparta; isotopic analy- Ocean, neotectonic features developed due to the continental ses were done at the Isotech Laboratories of Isothermal collision of Arabian and Anatolian plates, and in the whole Technology Limited, UK, and whole rock analyses were region due to the N–S compression, strike-slip fault sys- done at the ACME Laboratory, Canada. For the interpre- tems developed and in the weakness zones, such as opening tation of the isotope chemistry, evaluation of the analy- cracks, associated with these; volcanic lavas and pyroclastics ses was done according to the standard mean ocean water related to the collision occur (Keskin 1998). In Pasinler geo- (SMOW) stated by Craig (1961). This definition refers to thermal field, Pliocene aged Horasan formation comprises

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