Thermodynamic constraints on the origin of iron in ground water: the water supply of Tomsk, West Siberia, Russia

摘要

A significant part of the Russia territory is a province of Fe-rich ground water. We investigated the Fe sources in ground water of the Tomsk water supply (West Siberia).The range of Fe content of this water is generally 2-10 mg/l, and up to 19 mg/l. The major source is from the aquifer minerals, mainly aluminosilicates of the pyroxene and hornblende groups. According to lithological and mineralogical analyses, all terrigeneous rocks of this multi-layer artesian system contain these minerals. High concentrations of Fe in the fresh non-sulfate waters result from dissolution of aluminosilicates in the aquifers, and simultaneous formation of secondary phases with continuous concentration of compounds, which are mobile in this geochemical environment, as indicated by thermodynamic modelling. The high Fe concentrations in water are controlled by siderite, Fe-rich montmorillonites or illites, which precipitate Fe from the solution as saturation is reached.