Hydrogeochemical characteristics of underground waters in the suture zone of the Ufa brachyanticline and the Pre-Urals foreland basin
Authors:   Perm Federal Research Centre of the Ural Branch of RAS, KAZANTSEVA Alyona Sergeevna , KADEBSKAYA Ol’ga Ivanovna ,   Perm Federal Research Centre of the Ural Branch of RAS, DUBLYANSKIY Yuriy Viktorovich ,   Leopold-Franzens-Universität Innsbruck, KATAEV Valeriy Nikolaevich ,   Perm State University
Published: December 2020

During the period of long-term research, since the end of the XIX century, a large hydrogeochemical material has been accumulated within the suture zone of the Ufa brachyanticline and the Pre-Urals foreland basin. There are very few works on studying the conditions of natural water formation from the perspective of modern methodologies based on the study of variations in the isotope ratios of hydrogen and oxygen within the study area. The main goal of the work is to establish the conditions for the formation of the isotopic and chemical composition of groundwater of the Lower Perm aquifer complex, which is distributed within the suture zone of the Ufa brachyanticline and the Pre-Urals foreland basin, which belongs to the Kishert karst region. The features of the formation of the chemical and isotopic composition of groundwater in the suture zone of the Ufa brachyanticline and the Pre-Urals foreland basin in the Kishert region are analyzed based on data obtained in the period 2017–2018. In the Western part of the region, there is a watered zone associated with tectonic disturbances, where karst water is discharged. The chemical composition of the karst waters of the Kishert region has been studied quite fully. Data on the isotopic composition (deuterium and oxygen–18 content), which has been studied to a lesser extent, were used for a detailed study of the conditions for the formation of groundwater composition. In addition, the chemical and isotopic composition of precipitation and river water is considered. It is shown that the source at the Nizkoe village, discharging near the contact of carbonate-sulfate and terrigenous rocks, is characterized by the НСО3 –SO4 –Ca–Mg composition and mineralization 550,0–738,0 mg/dm3 , the source at the Zuevo village, which unloads within distribution of terrigenous rocks of the Kungurian stage, has a SO4 –Ca composition and high mineralization of 1623,0-2110,0 mg/dm3 . The isotopic composition of the two sources varies within rather narrow limits and is lighter than the weighted average value of atmospheric precipitation, which indicates that these sources are primarily recharge by light snow waters of the winter and spring periods. The waters of the lakes Molebnoe and Proval mainly НСО3 –Ca composition, they are characterized by vertical hydrochemical zonality associated with a change in chemical parameters. An increase in the mineralization of lake water indicates a groundwater inflow from sulfate (Proval lake) and carbonate (Molebnoe lake) sediments of the Kungurian stage. Lake waters have the heaviest and relatively stable composition due to the processes of evaporation from the surface and discharge of deep waters at the bottom of the lakes. The relationship between atmospheric precipitation, river waters and the waters of Proval lake and the source of the village of Nizkoe was established, and for the Zuevsky source only with river waters. A weak correlation was revealed for the Molebnoye lake with precipitation (r = 0,25) and river waters (r = 0,12).