Hydrogeochemical and isotopic monitoring of the Kestanbol geothermal field (Northwestern Turkey) and its relationship with seismic activity

Abstract

Kestanbol geothermal field is located in northwestern Turkey and is one of the highest temperature geothermal fields in the Biga Peninsula. In this study, one geothermal well, two geothermal springs and two cold springs were monitored for one year in Kestanbol geothermal field to determine hydrogeochemical and isotopic characteristics. Additionally, any possible relationship between seismic activity and variations in the hydrochemistry of geothermal water was investigated. The Kestanbol geothermal field is controlled mainly by the right-lateral strike-slip Kaplica fault with normal components. The distribution of the geothermal waters is roughly parallel to the fault. The temperature, electrical conductivity, salinity, and pH of the geothermal waters were within the range of 59.5 to 74.6 °C, 30300 to 35700 μS/cm, 19.6 to 23.3‰ and 6.13 to 6.83, respectively. The temperature interval was 11.2 to 25.4 °C for cold waters. The hydrochemical facies of the geothermal waters were Na-Cl type and the cold waters were the Ca-HCO 3 -Cl type. The high concentrations of As, Ba, Fe, Li and Mn in geothermal waters were mainly derived from prolonged water-rock interactions under high-temperature conditions. The δ 18 O and δ 2 H contents of cold waters indicated meteoric origin. The geothermal waters were enriched in δ 18 O and δ 2 H, and located on the mixing line between local groundwater and fossil seawater, indicating mixing processes. During our study period, 20 earthquakes with Mw 3.5 and above were recorded in the close surroundings of the Kestanbol geothermal field, and temporal variations in the physicochemical and chemical compositions of geothermal waters were observed. Concentrations Clof the geothermal waters exhibited decrease after the Tartisik-Ayvacik earthquake (Mw= 5.0), indicating more supplement of groundwater with shallow origin under the increase of tectonic stress.

Düşük Sıcaklıklı Bir Jeotermal Alanın İnsansız Hava Aracı Termal ve RGB Görüntüleri ile Modellenmesi: Kocabaşlar Jeotermal Alanı Örneği, Kuzeybatı Türkiye

“…Geothermal energy is independent of daily or seasonal weather fluctuations and the unpredictable fluctuations of international commodity prices (Jolie et al, 2021). Due to its geological and tectonic features, Türkiye has one of the highest geothermal energy potentials in the world, with more than 2000 geothermal and mineral springs (Vengosh et al, 2002;Şanlıyüksel Yücel et al, 2021). Monitoring geothermal springs is crucial for Türkiye to ensure the sustainable development of geothermal energy.…”