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The Camlidere prospect is located about 100 km NW of Ankara in northern Central Anatolia. Thermal springs discharge in volcanic terrain, often in clusters, along faults in 5 separate areas. The spring discharge temperatures are between 11 and 28 °C. Artesian flow of 4 wells (depths ranging from 100 to 1367 m) discharges Na-HCO3 and Ca-Na-HCO3 type thermal waters with temperatures changing between 27 and 42 °C. Cold springs at the fringe of the field are of Ca-HCO3 type. Constituents of minor elements (F, B, Fe, Ba, Rb, Cs, As and Sr) are incorporated in the thermal waters during deep water-rock interactions. Saturation indices indicate that mineralisation of the thermal waters involves dissolution of silicates, carbonates and ion exchange reactions. Mixing with surface waters and shallow groundwaters in the discharge areas modifies the geochemical character of the thermal waters. Isotopic data of Camlidere thermal waters (δ18O, δ2H, 3H) reflect their deep-circulating meteoric origin and indicate recharge areas between 1494 and 1833 m a.s.l. Such levels are supported by structural data and suggest that Camlidere thermal waters are recharged from the Aluc Mt. in the east and the Mahya Mt. to the west of Camlidere. Isotopic values also indicate a common recharge area (elevation) for deep groundwaters, but suggest different pathlengths required to account for variations in conductivity. Chemical geothermometry (K-Mg, quartz), alteration mineral assembleges and lack of δ18O enrichment indicate reservoir temperatures between 100 to–150 °C for the Camlidere area. The observed SiO2 values and inferred T(K-Mg) data indicate some advective (terrain controlled) shallow flows involving SiO2 re-equilibration of mixed thermal fluids. Long circulation time of meteoric waters within the basement rocks is also indicated by low tritium values of the thermal and mineral bicarbonate waters, although thermal waters do not achieve thermodynamic equilibrium. The Camlidere prospect hosts a low temperature, fracture-zone system with limited convective up-flow and dominant conductive heat transfer from a resource base in the upper crust to the surface. Based on acquired data, a conceptual model of the geothermal system of Camlidere is proposed.

The Taskesti–Sariot study area is located in northwest Turkey, about 23 km NW of Mudurnu town in the Bolu province. The thermal waters of the Taskesti–Sariot were investigated by means of field measurements, chemical analyses and isotope investigations. An area of 20 km2 was geologically mapped around the spa and characteristics of thermal and cold-waters were determined. The Taskesti-Sariot thermal waters, (T °C = 63, and flowrate of 1.70 L/sec) emanates along a secondary fault in the North Anatolian Fault Zone (NAFZ). Geothermal water reservoirs are present within fractured limestone, micaschists, diorite, tonalite, serpentinite, gabbropegmatites and graywacke which have the secondary porosity and permeability. Based on the main consitituents, the thermal waters can be classfied as Na(Ca)SO4 types, whereas the cold and stream waters were characterized as a Ca(Mg)HCO3 type waters. Geochemical processes responsible for the genesis of the hydrochemical features of the waters include dissolution, mixing, oxidation and loss of energy by heat conduction. Chemical geothermometers suggest deep temperatures close to 100 °C for the deepest geothermal well (SK-1: 63 °C at the surface) water in the region and thus the Taskesti-Sariot geothermal system can be classified as a low temperature resource. These thermal waters are of meteoric origin that circulate and restores heat through the fault zone due to the geothermal gradient and discharge to the surface. The thermal waters are derived from advective flow as indicated by the δ2H and 18O isotope data, which plot on the meteoric water line showing a significant downward shift if compared with a local reference point thus indicating recharge by infiltration derived from a high standing (colder) terrain. The recharge area for the thermal waters is estimated to be nearly 1000 – 1600 m from the northeast part of the study area. Moreover, there is no evidence for isotope exchange between hot waters and reservoir rock. Tritium data confirm the deep origin of the thermal waters. Finally, a conceptual geochemical model of the geothermal system is proposed.

Kizilcahamam geothermal area is one of the most important geothermal fields in the Galatean Volcanic Province northern Central Anatolia of Turkey. Kizilcahamam geothermal field is liquid-dominated system that have been developed in the rugged terrain, and usually consists of a geothermal systems that occur commonly associated with terrestrial volcanism. This field is characterized by thermal and mineralized springs, travertine, with wide alteration zones. Thermal waters are issue through the faults and fracture zones of the volcanics. The temperatures of the wells in the Kizilcahamam town center varies between 42 and 81 °C, whereas the temperature of thermal and mineralized water springs in the area of Acisu Stream and Seyhamam varies between 23 and 43 °C. Electrical conductivity values for thermal waters are between 1029 and 3700 μS/cm. Thermal waters in Kizilcahamam area are mainly Na-HCO 3 -Cl and Na-Ca-HCO 3 type, with high salinity, while cold groundwater is mostly of Ca (Na, Mg)-HCO 3 type, with lower salinity. Both waters of Kizilcahamam town center and Acisu Stream appear to be derived from a deeper reservoir fluid, whereas Seyhamam thermal waters are compatible with shallow cold waters heated by steam absorbing high temperatures. High contents of some minor elements in thermal waters, such as F, B, Li, Rb, Sr and Cs probably derive from enhanced water–rock interaction. The isotopic values of thermal water (δ 18 O, δ 2 H, δ 3 H) indicates their deep-circulating meteoric origin and allow estimation of infilitration altitude ranging between 1350 and 1750 m.a.s.l.This datum, supported by structural data, suggests the Isikdag and Alucdag Mountains as the recharge area of the system. As frequently observed in many geothermal systems positive I8 O shifts of Kizilcahamam thermal waters relative to the local meteoric line were considered to be primarily due to interaction with host rocks at elevated temperature (T > 150 °C) and from CO 2 exsolution of thermal and mineral springs. In this system, geothermal waters are heating by an intrusive-cupola and geothermal gradient, followed by the waters rising to the surface along faults and fractures that act as hydrothermal conduits. A conceptual hydrogeochemical model was developed for a hydrogeological flow system in the Kizilcahamam Region.

Faults related to the neotectonic stress regime of Eastern Anatolia permit the rise and outflow of thermal waters in the Zilan Valley located 30 km north of the Ercis, Van province. Thermal springs discharge in a volcanic terrain, often in clusters, along faults in two separate areas: In the vicinity of Taskapi (Sorkoy) and Gergili villages, which lie in the north of the area; and in the area of Hasanabdal (Doganci) thermal springs that lie to the south of the Zilan Valley. Temperatures of the springs range from 20 to 78 °C, with discharge rates of 4−20 L/s. Thermal waters of the Zilan region are of different types, from Na−HCO3 to Na-Cl, with dissolved ion concentrations varying over a wide range between 484–4572 mg/L. Calcite dissolution and silicate hydrolysis are the dominant water-rock interactions. Constituents with minor and trace element concentrations reinforce conclusions drawn from major-ion composition that the major hydrogeochemical processes are: mixing between cold-shallow and hot-deep waters, loss of energy by heat conduction, and steam-heating of perched-aquifers. The cold spring and Zilan Creek waters are of the Ca−HCO3 and Na−HCO3 type respectively, and their dissolved ion concentrations are low. Hydrogeochemical processes for the cold waters involve carbonate dissolution and silicate weathering reactions. Chemical geothermometers are used to estimate the temperature of the deep fluids using the chemical composition of the less modified fluids. They indicate that fluids emerging from volcanic rocks in the Zilan valley reach temperatures of around 150 °C. Thermal waters, generated through conductive heat transfer or the input of geothermal vapor or gases from below, delineate the extent of the geothermal reservoir(s) at depth. Deuterium and oxygen-18 signatures of thermal waters indicate that they are at least partially derived from thermally heated water through a process of 18O enrichment owing to interaction with the marine limestones through which the water passes to the surface springs. Both geochemical and isotope data indicate that the Zilan Valley hosts a low temperature, fracture-zone system with aconvective up-flow and dominant conductive heat transfer from a resource base in the upper crust to the surface. Ore deposits in the Zilan Valley, hydrothermal alteration in the Sorkoy lava, and high concentrations of As, Au, Hg, Zr, Ba, Ni, Sb and other trace elements that are present in the travertine is the evidence for a heat source formed at a shallower depth. A conceptual model of the geothermal system of Zilan is proposed based on adata gathered.

The Kesenozu thermal springs are located in northwestern Turkey, about 10 km south of Seben. The springs emerge from a fracture zone created by strike-slip faulting that strikes north–northwest, along the Hamambogazi Creek, in northwestern Anatolia. The reservoir comprises a steeply dipping fracture zone and deep, feeding aquifers hosted by limestones and conglomerates of the Kesenozu Formation. Eight springs and one shallow well discharge thermal water at a total rate of about 44 l/s with temperatures between 42 and 78 °C. The waters are of neutral pH, NaHCO3 type. The meteoric origin of the spa waters is evident from their chemical and isotopic (18O, 2H, 3H) compositions. The thermal system is driven by deep-reaching advective flows where rainwater becomes heated on descent, and after deep paths ascend along fractures that act as hydrothermal conduits. It can be described as an advective geothermal system. Silica (chalcedony) geothermometry indicates equilibrium temperatures between 89 and 94 °C. A recently drilled deep well encountered similar temperatures at about 2 km depth. The minimum heating power potential (direct use) of the fracture zone reservoir is about 10 MWth.

The Diyadin Geothermal area, located in the eastern part of Anatolia (Turkey) where there has been recent volcanic activity, is favorable for the formation of geothermal systems. Indeed, the Diyadin geothermal system is located in an active geodynamic zone, where strike-slip faults and tensional cracks have developed due to N–S regional compression. The area is characterized by closely spaced thermal and mineralized springs, with temperatures in the range 30–64 °C, and flowrates 0.5–10 L/s. Thermal spring waters are mainly of Ca(Na)-HCO 3 and Ca(Mg)-SO 4 types, with high salinity, while cold groundwater is mostly of Ca(Na, Mg)-HCO 3 type, with lower salinity. High contents of some minor elements in thermal waters, such as F, B, Li, Rb, Sr and Cs probably derive from enhanced water–rock interaction. Thermal water samples collected from Diyadin are far from chemical equilibrium as the waters flow upward from reservoirs towards spring vents and possibly mix with cooler waters. The temperatures of the deep geothermal reservoirs are estimated to be between 92 and 156 °C in Diyadin field, based on quartz geothermometry, while slightly lower estimates are obtained using chalcedony geothermometers. The isotopic composition of thermal water (δ 18 O, δ 2 H, δ 3 H) indicates their deep-circulating meteoric origin. The waters are likely to have originated from the percolation of rainwater along fractures and faults to the deep hot reservoir. Subsequent heating by conduction due to the presence of an intrusive cupola associated with the Tendurek volcano, is followed by the ascent of deep waters to the surface along faults and fractures that act as hydrothermal conduits. Modeling of the geothermal fluids indicates that the fluid is oversaturated with calcite, aragonite and dolomite, which matches travertine precipitation in the discharge area. Likewise, the fluid is oversaturated with respect to quartz, and chalcedony indicating the possibility of siliceous precipitation near the discharge areas. A conceptual hydro-geochemical model of the Diyadin thermal waters based on the isotope and chemical analytical results, has been constructed.

The Kozakli-NevAYehir geothermal field extends a long a NW-SE direction at SE of the Centrum of Kozakli. The area is not rugged and average elevation is 1,000 m. The Kozanozu Creek flows towards north of the area. In the Kozakli thermal Spa area, thermal waters are manifested along a valley with a length of 1.5 km and 200 m width. In this resort some hot waters are discharged with no use. The thermal water used in the area comes from wells drilled by MTA. In addition, these waters from wells are also utilized by hotels, baths and motels belonging to City Private Management, Municipality and private sector. The measured temperature of Kozakli waters ranges from 43-51A degrees C in springs and 80-96A degrees C in wells. Waters are issued in a wide swampy area as a small group of springs through buried faults. Electrical conductivity values of thermal spring and well waters are 1,650-3,595 mu S/cm and pH values are 6.72-7.36. Kozakli cold water has an electrical conductivity value of 450 mu S/cm and pH of 7.56. All thermal waters are dominated by Na+ and Cl-SO4 while cold waters are dominated by Ca+2 and HCO3 (-). The aim of this study was to investigate the environmental problems around the Kozakli geothermal field and explain the mechanisms of karstic depression which was formed by uncontrolled use of thermal waters in this area and bring up its possible environmental threats. At the Kozakli geothermal field a sinkhole with 30 m diameter and 15 m depth occurred in January, 17th 2007 at the recreation area located 20 m west of the geothermal well which belongs to the government of NevAYehir province. The management of the geothermal wells should be controlled by a single official institution in order to avoid the creation of such karstic structures affecting the environment at the source area.

The Terme and Karakurt thermal resorts are located in the center of KirAYehir city in central Anatolia. Thermal waters with temperatures of 44-60A degrees C are used for central heating and balneologic purposes. Paleozoic rocks of the KirAYehir Massif are the oldest units in the study area. The basement of the Massif comprises Paleozoic metamorphic schist and marbles which partly contain white quartzite layers of a few tens of cm thickness. The metamorphic schists which are cut by granites of Paleocene age are overlain by horizontally bedded conglomerate, sandstone, claystone, and limestone of upper Paleocene-Eocene age. Among the thermal and cold waters collected from the areas of Terme and Karakurt, those from thermal waters are enriched with Ca-HCO3 and cold waters are of Ca-Mg-HCO3 type waters. The pH values of samples are 6.31-7.04 for the thermal well waters, 6.41 for thermal spring, 7.25 and 7.29 for the cold waters, and 7.52 for the Hirla lake water. EC values are 917-2,295 mu S/cm for the thermal well waters, 2,078 mu S/cm for thermal spring, and 471 and 820 mu S/cm for the cold springs. The lowest TDS content is from water of T10 thermal well in the Terme area (740.6 mg/l). The hot and cold waters of Terme show very similar ion contents while the Karakurt hot waters at western most parts are characterized by distinct chemical compositions. There is ion exchange in thermal waters from the T5 (5), T6 (6), T12 (7), and T1 (8) wells in the Terme area. The thermal waters show low concentrations of Fe, Mn, Ni, Al, As, Pb, Zn and Cu. Waters in the study area are of meteoric origin, and rainwater percolated downwards through faults and fractures, and are heated by the geothermal gradient, later rising to the surface along permeable zones. delta C-13(VPDB) values measured on dissolved inorganic carbon in samples range from -1.65 to +5.61aEuro degrees for thermal waters and from -11.81 to -10.15aEuro degrees for cold waters. Carbon in thermal waters is derived from marine carbonates or CO2 of metamorphic origin while carbon in cold waters originates from freshwater carbonates.

In the Kozakli geothermal province, thermal waters are manifested along a valley 1.5 km long and 200 m in width. Thermal waters utilised by the resort and some other hotels are mostly discharged from bore wells. The issuing temperatures of the thermal waters vary from 40-50 degrees C in thermal springs and 45-96 degrees C in bores and open wells. The geochemical and isotopic signatures of the thermal water suggest mixing of thermal waters with formation waters and cold near-surface groundwaters before emerging to the surface, and hence geochemical indicators fail to indicate the near true reservoir temperatures. However, the oxygen and hydrogen isotopic signatures strongly suggest a high temperature reservoir (>220 degrees C) in the crystalline basement rocks. Long circulation of meteoric waters within the basement rocks is indicated by low tritium values in the thermal waters. Major involvement of Miocene Marls in modifying the chemical signatures of the thermal waters is inferred from the trace element concentrations. (C) 2011 Elsevier B.V. All rights reserved.