Seben–Kesenözü low-temperature geothermal prospect, NW Turkey: study of an advective geothermal system

The Kesenözü 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 Hamamboğazi Creek, in northwestern Anatolia. The reservoir comprises a steeply dipping fracture zone and deep, feeding aquifers hosted by limestones and conglomerates of the Kesenözü 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.