Hydrochemistry and environmental isotope study of the geothermal water around Beypazari granitoids, Ankara, Turkey

摘要

Hydrochemical analysis results suggest four different water types: bicarbonate dominant water (facies-I), sulfate dominant cold brine water (facies-Ⅱ), sodium-bicarbonate dominant thermal water and thermal and mineralized water (facies-Ⅲ), and sulfate-chloride dominant thermal and mineralized water (facies-Ⅳ). The mineral content/salinity of the water is related to the ions that these waters dissolve from the minerals on the rocks during infiltration and circulation in the saturated zone. Gypsum cover units that exist on the granitoids in the region is the main factor for the ion increase in the facies Ⅲ geothermal water similar to the cold brine water (facies Ⅱ). Isotopic analyses indicate that the thermal springs (Dutlu bath spring, Ayas, bath well, Qoban bath well and Kapullu bath spring) are of meteoric origin and receive recharge from precipitation in the Beypazari granitoids and around gypseous formations with elevations of about 950-1,150 m. Karakaya bath well and Ilica bath spring thermal water points are recharged from the Bilecik limestone hills, Tekke volcanics and Incedoruk Formations. Karakoca mineral spring of thermal and mineralized water is recharged from out of the study area. According to oxygen-18 (SO_4~(2-)) and sulfur-34 (SO_4~(2-)) contents, sulfate in water samples from Ayas and Dutlu resorts as well as Qoban bath is derived from the gypsum of Kirmir Formation as the primary source. Sulfates of the Kapullu bath water and Karakoca mineral water originate from secondary sources such as pyrite oxidation and bacteriological reduction.