Gültekin Tarcan

Water geochemistry of the Seferihisar geothermal area, İzmir, Turkey

Abstract The Na–Cl thermal waters of Seferihisar have measured temperatures of 30–153°C, and conductivities of 7400–55200 μS/cm. They issue from Upper Cretaceous to Paleocene Bornova melange rocks, which are made up of sandstone–shale intercalations, conglomerate, mafic submarine volcanics, limestone lenses, serpentinite and limestone bodies, and their complexes, through the intersection of faults. The clay-rich zones of the overlying Neogene terrestrial sediments cap the system. The heat source is the high geothermal gradient caused by graben tectonics of the area. Na and Cl ions mainly dominate the chemistry of thermal waters, thus thermal waters of the Seferihisar area appear to be mixtures of groundwaters and seawater. The seawater contribution in thermal waters varies from 10% to 80%. Assessments from empirical chemical geothermometers, mineral equilibria and silica-mixing model applied on the thermal waters of the Seferihisar geothermal area suggest that the temperatures of the reservoir systems vary between 60 and 180°C. The Seferihisar geothermal area has been physically divided into five main groups and estimated reservoir temperatures provided by the entire methods give the increase as: Doganbey Burnu, Karakoc spa, Doganbey, Tuzla and Cumali spa areas in ascending order of reservoir temperature. Hydrogeochemical assessments indicate that thermal waters were mixed with cold waters before and/or after heating at depth in different proportions. The results of mineral equilibrium modeling indicate that the thermal waters of Seferihisar are undersaturated with respect to gypsum and amorphous silica, oversaturated with respect to calcite, dolomite and aragonite, and undersaturated or oversaturated with respect to quartz, chalcedony and anhydrite.

Hydrogeochemistry of the Simav geothermal field, western Anatolia, Turkey

Thermal waters hosted by Menderes metamorphic rocks emerge along fault lineaments in the Simav geothermal area. Thermal springs and drilled wells are located in the Eynal, Citgol and Nasa locations, which are part of the Simav geothermal field. Studies were carried out to obtain the main chemical and physical characteristics of thermal waters. These waters are used for heating of residences and greenhouses and for balneological purposes. Bottom temperatures of the drilled wells reach 163°C with total dissolved solids around 2225 mg/kg. Surface temperatures of thermal springs vary between 51°C and 90°C. All the thermal waters belong to Na–HCO3–SO4 facies. The cold groundwaters are Ca–Mg–HCO3 type. Dissolution of host rock and ion-exchange reactions in the reservoir of the geothermal system shift the Ca–Mg–HCO3 type cold groundwaters to the Na–HCO3–SO4 type thermal waters. Thermal waters are oversaturated at discharge temperatures for aragonite, calcite, quartz, chalcedony, magnesite and dolomite minerals giving rise to a carbonate-rich scale. Gypsum and anhydrite minerals are undersaturated with all of the thermal waters. Boiling during ascent of the thermal fluids produces steam and liquid waters resulting in an increase of the concentrations of the constituents in discharge waters. Steam fraction, y, of the thermal waters of which temperatures are above 100°C is between 0.075 and 0.119. Reservoir pH is much lower than pH measured in the liquid phase separated at atmospheric conditions, since the latter experienced heavy loss of acid gases, mainly CO2. Assessment of the various empirical chemical geothermometers and geochemical modelling suggest that reservoir temperatures vary between 175°C and 200°C.

The Effects of Colemanite Deposits on the Arsenic Concentrations of Soil and Ground Water in Igdeköy-Emet, Kütahya, Turkey

The hydrochemical study of the area surrounding the Hisarcık (Emet-Kütahya) colemanite mine shows extremely high arsenic contamination in ground water between 0.07 to 7.754 mg L-1. This contamination in and around the Igdeköy village of Emet was caused by naturally occurring arsenic dissolution from a borate bearing clay zone due to the leaching of arsenic bearing minerals. The arsenic concentration in the ground water varies locally from spring to spring and is related to the mineralogical and geochemical compositions and lithofacies of the contaminant aquifer. The Neogene borate-bearing clay unit, which contains some arsenic minerals such as realgar (AsS) and orpiment (As2S3) observed in colemanite (Ca2B6O11⋅5H2O) nodules, is responsible for the arsenic contamination in ground waters in the study area. Soil geochemical analyses show unremarkable concentrations, varying from <0.01 to 7.11 mg kg-1.

Hydrogeochemical and hydrogeological investigations of thermal waters in the Emet area (Kütahya, Turkey)

Metamorphic rocks host the majority of the thermal waters of the Emet area. Only Dereli springs are hosted by nonmetamorphic carbonates and ophiolitic rocks. The carbonated rocks of the lower parts of the Neogene sequence are also secondary reservoir rocks. The measured surface temperatures of thermal waters are between 33 and 54 C. Most of the thermal waters are characterized as Ca–Mg–SO4–HCO3 type although there are a few Ca–Na–HCO3, Na–Ca– SO4 and Ca–Mg–HCO3 waters. Calcium concentrations in the thermal waters are 89–354 mg/kg. High SO4 contents of the thermal waters (up to 1309 mg/kg) are related to rocks and minerals in the Red Unit below the Emet borate deposits. Although the SO4 concentrations are high and SO4 is the major anion, gypsum and anhydrite are undersaturated for all of the thermal waters indicating that dissolution of SO4 is still taking place in the reservoir. Thermal waters are oversaturated at outlet conditions with respect to calcite, chalcedony, dolomite and quartz. According to the activity diagrams thermal waters are likely to form illite as an alteration product in the reservoir and Ca and Mg contents are controlled by exchange with smectite. Reservoir temperatures obtained by silica geothermometers and assessments of the saturation states of minerals are more appropriate for Emet geothermal waters. Assessments of the various geothermometers suggest that reservoir temperature is around 75–87 C.

Review of water and soil contamination in and around Salihli geothermal field (Manisa, Turkey)

The town of Salihli is situated in Gediz Graben in the western Anatolia. This region is important in terms of industry, mining, geothermal energy, water sources, and agricultural production. Geothermal flow and anthropogenic activities in Salihli threaten the surrounding environment due to the contamination of cold groundwater, surface water, and soil. The goal of the present study is to determine the environmental effects of the geothermal and anthropogenic activities in Salihli on soil, stream sediments, and water. Stream sediments and farm soil have been contaminated by substances derived from geothermal and industrial effluents. To this end, the quality review of the water was completed and the heavy metal levels in stream sediment samples were measured to determine the extent of contamination. The elements As, B, Br, Fe, and Ni are the major contaminants present in surface water and groundwater in the study area. The concentrations of these elements excess tolerance limits of international water standards. Gibbsite, K-mica, kaolinite, sepiolite, halite, sulfur, willemite, and Pb(OH)2 might be precipitated as scales at low temperatures on the soil; this could be interpreted as a resultant from soil contamination. The concentrations of 17 elements (As, Ba, B, Cd, Co, Cr, Cu, Fe, Hg, Li, Mo, Mn, Ni, Pb, Sb, Sr, and Zn) were measured in samples from stream sediments and surface soils. In the study area, especially geothermal and anthropogenic activities give rise to environmental pollution.

Hydrogeochemical study of the gümüşköy spa (Aydin) and its vicinity

Gümüşköy Kaplıcası Batı Anadolu Bölgesi’nde Büyük Menderes Grabeni’nin güneybatı kısmında yer almaktadır. İnceleme alanındaki termal suların kaynak çıkış sıcaklıkları 20-36 °C, pH değerleri 6.4-7.5 ve elektriksel iletkenlikleri (EC) 2000-11230 μS/cm arasındadır. Termal sular genel olarak Na-Cl su tipindedirler. Jeotermal sistemin rezervuar kayaçları Menderes Masifi’nin karstik mermerleri ve çatlaklı şist birimleridir. Neojen’in geçirimsiz birimleri jeotermal sistemin örtü kayalarını oluşturmaktadır. Sistemin ısı kaynağı ise tektonizmaya bağlı yüksek jeotermal gradyandır. Termal sular Giggenbach Diyagramı’na (1988) göre çoğunlukla ham sular sınıfındadır ve kimyasal jeotermometrelerle hesaplanan rezervuar sıcaklıkları 55-114 °C arasında değişmektedir. Ölçülmüş sıcaklıklardaki mineral doygunlukları, termal sularda genellikle kalsit, aragonit ve dolomit minerallerinin çökel oluşturduğunu gösterir. Suların jips, anhidrit, sölestin ve barit minerallerini ise çözündürücü özellikte oldukları görülmektedir. Termal suların üretim ve iletim hatlarında ve atık suların reenjeksiyonu sırasında kalsit, aragonit ve dolomit minerallerinin kabuklaşma riski oluşturacağı belirlenmiştir. Silis mineralleri ise kinetik özelliklerinden dolayı amorf silis özelliğinde çökelebilir. Gümüşköy Spa is located in southwest of the Büyük Menderes Graben in Western Anatolia. The thermal waters of the area have spring temperatures of 20-36 °C, pH of 6.4-7.5 and EC of 4960 to 5079 μS/cm. Water type of thermal waters is generally Na-Cl type. Reservoir rocks of geothermal systems are marble and fissured schist units of Menderes Massif. Impermeable units of Neogene are the cap rocks of geothermal systems. Heat source of system is also geothermal gradient connected with tectonism. According to Giggenbach Diagram (1988), thermal waters mostly fall into the immature fields and reservoir temperatures vary between 55-114 °C. Mineral saturation in outlet temperatures indicates that calcite, aragonite, and dolomite minerals are generally oversaturated in the thermal waters. However, it is seen that the thermal waters is undersaturated with gypsum, anhydrite, celestite, and barite. It is determined that calcite, aragonite and dolomite minerals will be created scaling risk in production and conduction line of the thermal waters and during the reinjection of waste water. Silica minerals may also precipitate amorphous silica due to kinetic properties.