Equilibrium of soda groundwater of coal beds of Naryksko-Ostashkinskaya area (Kuzbass) with minerals of containing rocks

In this article, on the example of the groundwater of Naryksko-Ostashkinskaya area of the central part of Kuzbass, are given the geological structure, hydrogeological features, chemical composition of waters and results of calculation of equilibrium with the most common carbonate and aluminosilicate minerals of containing rocks most spread in the geological section of the studied territory. In the Naryksko-Ostashkinskaya territory there is a direct vertical hydrodynamic division according to the intensity of water exchange into two distinct zones: the active and slowed-down water exchange. Water of both zones differ in chemical and gas composition and submit to direct vertical hydrogeochemical zoning. Of particular interest is the slowed-down water exchange zone, not only its higher salinity (from 1 and less often 0.4-1.2 to 10-19, g/l), but also the composition of water. It is almost universally soda water (HCO ₃-Na), characteristic for all Kuzbass with a pH of 7.5 to 9.9. Thermodynamic calculations of water showed non-equilibrium with primary (endogenous) minerals which they dissolve, but at the same time equilibrium with clays and carbonates that precipitate in water. Almost all water is supersaturated with respect to calcite and siderite, to dolomite and magnesite in part. Therefore, in these conditions feldspars, pyroxene, epidote and hornblende are actively dissolved, i.e. primary minerals which are unstable in these conditions and respectively act as a source of Ca, Mg, Na, Fe, K, Si, Al, etc. Water is in equilibrium with albite because of high value of рН and high concentration of Na, therefore, it does not dissolve it. Thus, water filtered through rocks dissolves endogenous minerals (except albite) which are not in equilibrium and is enriched respectively with Na, Ca, Mg, K, Si, Al and other elements. Some elements are out of the solution immediately and become secondary deposits: oxides and hydroxides, clays, carbonates which do not dissolve under these conditions but are formed. Carbonates connect Ca, Mg, Fe, C, clay minerals - Al, Si, Ca, Mg, Fe, partially Na and K, albite - Na, Al, Si, potash feldspar - K, Al, Si, oxides and hydroxides - Fe, etc. Na less of all becomes a secondary deposit; therefore, it continues to concentrate in water and the composition of water remains soda. A part of minerals remains in nonequilibrium with water all the way of its movement and continues to be dissolved. First of all, it is Ca, Mg and Fe aluminosilicates of endogenous genesis, water is always in non-equilibrium with them.

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