Abstract
The Şavşat (Artvin, Turkey) Geothermal Field (ŞGF) is located on the northeastern border of Turkey. This field is characterized by thermal and mineralized springs and travertine. The temperature of the thermal water is 36 °C, whereas that of the mineralized spring in the area is approximately 11 °C. The Na–HCO3–Cl-type thermal water has a pH value of 6.83 and an EC value of 5731 µS/cm. The aim of this study is to characterize the geothermal system by using geological, geophysical, and hydrogeochemical data and to determine its hydrochemical properties. A conceptual hydrogeological model is developed for the hydrogeological flow system in the ŞGF. According to the hydrogeological conceptual model created by geological, geophysical, and hydrogeochemical studies, the reservoir comprises volcanogenic sandstone and volcanic rocks. The cap rock for the geothermal system is composed of turbiditic deposits consisting of mudstone–siltstone–sandstone alternations. An increase in the geothermal gradient is mainly due to Pleistocene volcanic activity in the field. The isotopic values of thermal water (δ18O, δ2H, δ3H) indicate a deeply circulating meteoric origin. The estimated reservoir temperature calculated by silica geothermometers is 100–150 °C, and the mixing rate of cold groundwater with geothermal waters is approximately 70%. It may be possible to obtain warmer fluids from a 300-m-deep borehole cutting through a fracture zone identified by geophysical studies. Heating by conduction via the geothermal gradient resulting from young volcanic activity drives geothermal waters upwards along faults and fractures that act as hydrothermal pathways. The positive δ13CVPDB value (+ 4.31‰) indicates a metamorphic origin for the thermal water. The 34SCDT value (~ 10‰) shows that the sulfur in the geothermal water is derived from volcanic sulfur (SO2).
Highlights
The Şavşat Geothermal Field (ŞGF) is located in northeast Turkey on the border with Georgia (Fig. 1)
The Şavşat (Artvin-Turkey) Geothermal Field contains outcrops of volcanic, volcano sedimentary, and sedimentary units formed during the late Cretaceous to the Pliocene– Pleistocene time periods
The artesian water recharging from a 120-m-depth borehole in the ŞGF has a temperature of 38 °C, an electrical conductivity (EC) value of 5731 μS/cm, and a pH of 6.83
Summary
The Şavşat Geothermal Field (ŞGF) is located in northeast Turkey on the border with Georgia (Fig. 1). Geological and geophysical studies and hydrogeochemical and isotope techniques have been widely used elsewhere to determine the hydrodynamic structure of geothermal systems in recent years (Tarcan et al 2005; Piscopo et al 2006; Schaffer and Sass 2014; Yurteri and Şimşek 2017; Uzelli et al 2017). In this geothermal field, there has not been any study that employs a conceptual approach based on hydrogeological and hydrogeochemical studies, such as hydrochemical facies compositions, isotopic features, water–rock interactions, mixing processes, and reservoir temperature. Establishing a hydrogeologic conceptual model can further help to determine flow paths, including recharge through flow–discharge processes, as well as mixing behavior
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