Chemical and isotopic composition of nitrogen thermal waters of the Kuldur Deposit (JAR, Russia)

Abstract

The article presents the results of the hydrogeochemical study of thermal groundwaters from the Kuldur spa (Jewish Autonomous Region, Russia). The main characteristics of these groundwaters are high temperature (73 ᵒС), low TDS (up to 0,38 g/l), and alkaline (pH 9). The dominated cation is sodium, and the anion is hydrocarbonate. Water is enriched with fluorine, silicon, aluminum, tungsten, molybdenum, and some other anionic elements. This study provides detailed data on the chemical and mineral composition of host rocks and sources of solutes. Isotopic data from bubbling gases show that the main component of the gas phase (N2) comes from an atmogenic source, while CH4 and CO2 are biogenic. Argon and oxygen are also derived from air, while helium is predominantly radiogenic. The ϬD and Ϭ18О in the aqueous phase indicate the undoubtedly meteoric genesis of groundwater with an extended circulation period. Our results suggest that the studied groundwaters are results of the penetration of meteoric waters to 4 km depth and heating up to 100 ᵒC. The solutes come to aquifer via the dissolution of rocks, but since groundwater circulates within the poorly soluble rock (granitoids), respectively, the water TDS remains low.