Interaction of thermal waters with carbonate and aluminosilicate minerals: A case study of Bang mineral hot spring, Central Vietnam

Results of the studies of water-rock interactions for the Bang thermal water system (Bang Mineral Hot Spring) in Kuang Binh province, Central Vietnam, are presented for the first time. It was established that the thermal waters (62.1-97.1 °C) with total mineralization of 255-659 mg/dm³ of HCO₃-Na composition are supersaturated with respect to carbonate minerals (calcite, magnesite, and dolomite) and saturated with respect to albite, microcline, laumontite, and glaucophane. The waters with the outlet temperature of 24.3-34.5 °C, with mineralization 44-87 mg/dm³ and composition HCO₃-Cl-Na-Mg are unsaturated with respect to carbonates and are in the fields of stability of clay minerals: kaolinite, illite, Na-, Ca-, and Mg-montmorillonite. Theseresults are in good agreement with the results of the isotope composition analysis of the hydrothermal vents (δD, δ¹⁸O and ³H), according to which the time of water circulation for the first-group is higher than 60 years and may reach more than 1000 years, while for the second-group water it does not exceed 50 years.