ИЗОТОПНЫЕ ОТНОШЕНИЯ СТРОНЦИЯ 87Sr/86Sr В ВОДЕ РЯДА РЕК ЮЖНОГО УРАЛА

Abstract

87Sr/86Sr isotopic ratios are widely used to identify strontium sources and study strontium behaviour in (bio)geochemical cycles. 87Sr/86Sr in surface waters can reflect the average composition of bioavailable (i.e. available for further absorption by plants and animals) strontium in the catchment specific area. Based on those 87Sr/86Sr ratios, the regional maps of the bioavailable strontium distribution (strontium isoscapes) can be compiled. A complex block structure characterizes the Ural mountain system. Individual parts (blocks) are composed of rocks of various ages, genesis and geochemical characteristics, which can radically change at a distance of several tens of kilometres. Such variability would be reflected in strontium isotopic ratios, thus making it possible to determine the local isotopic signatures of bioavailable strontium. This work aimed to study 87Sr/86Sr in the water in the rivers of the Southern Urals. We determined the contents and isotopic ratios of strontium in river water samples collected from the territories of the Orenburg and Chelyabinsk regions and the Republic of Bashkortostan in 2019-2020. For the first time in the surface water of the rivers in the Southern Urals (Ural, Belaya, Tobol, Karagaily-Ayat, Sim, and others), the 87Sr/86Sr isotopic ratios have been determined, and their variations have been analyzed. 87Sr/86Sr values vary in the range 0.70666-0.71063 (average 0.70908) for the rivers of the Urals basin, 0.70749-0.71058 (average 0.70924) for the Kama-Volga basin, 0.70946-0.71176 (average 0.71071) for the Tobol basin. Such features of the strontium isotopic composition may be due to the influence of underlying rocks of the catchment area drained by river water. The data obtained can be used to identify the sources of strontium input into the water system during hydrological and environmental studies; to confirm the authenticity of food products of plant and animal origin; to carry out comparisons in the studies of the migration of ancient people and animals, as well as to determine the raw material areas for the production of vegetable and woollen textiles and wooden products in antiquity. © 2022 Institute of the Earth's Crust. All rights reserved.