Trace elements in highly alkaline water in the Chulymskaya well ("Omega", Tomsk Region)

In the article the spatial distribution, geological and hydrogeological conditions, the unique chemical composition of groundwater of the Chulym basin are investigated. Uniqueness of them is that they are very fresh (salinity 0.25-0.6 g/l), but highly alkaline (pH 9.110.3). Such alkaline water is known in some parts of the world and is associated with igneous rocks. It is shown that alkaline water in the basin of the Chulym distributed in sedimentary rocks: sands, sandstones and siltstones of the Ilekskaya suite. Here, in the Cretaceous and Jurassic deposits, at depths of 600-1300 m the hydrogeological conditions are favorable for the formation of fresh groundwater: flow of fresh fractured water of the Altai-Sayan mountain framing in the deep faults zone towards the basin, large capacities of sandstones with high porosity, absence of pronounced aquiclude. The composition of water in the Chulymskaya well is studied in most detail, where the drinking medicinal table water "Omega" is got. This water is highly alkaline, sodium, infiltration by genesis; they circulate in the zone of active water exchange, which was confirmed by the chemical, gas and isotopic compositions. By the composition these water are similar to the nitrogen therms of Zabaikalye. Also we studied the published data of the chemical composition of 12 wells in the area, where water similar in composition was found at depths of 300-2000 m: fresh sodium with relatively alkaline reaction (pH 8 to 9). It is the first time that we have studied the trace elements of water by the mass spectral method of analysis (ICP-MS) based on the three samples analyzed in two different organizations: in the chemical analysis center Plazma (Tomsk) and in the Laboratory of Geosciences and Environment of Toulouse (CNRS, France). The result confirmed the origin of water as infiltration, the previous conclusion had been made by the results of isotopic and chemical analyzes. All elements, except Na, Si, Sc, I, Ga and As, do not exceed the average value on waters of the hyper-genesis zone. Elements such as Ti, Co, Ni, Se, Nb, Ag, Ta, Re, Nd, Eu, Gd, Yb, Lu, Th are present in the contents below the detection limit. In such alkaline conditions anionic elements migrate better, which explains the excessive Si, I and As. Cationic elements and complex elements in migrate worse the alkaline environment. Exceptions are Sc and Ga. The excess of scandium is by 50 times, the study of the reasons of this phenomenon will be the next stage of the research of these unique waters.

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