Using the X-ray phase method, the mineral composition of modern mineral sediments of Lake Salda in Turkey was studied. It has been established that the deposits are represented by hydromagnesite Mg5(CO3)4(OH)2×4H2O, guntite CaMg3(CO3)4 and a mechanical admixture of enstatite Mg2Si2O6. The role of organic components (cyanobacteria and diatoms) in the formation of carbonate mineral sediments is noted.

The findings of pyrite in the Novoafonskaya cave and its environs were studied using X-ray phase and mass spectrometric analyses. Pyrite oxidized from the surface, forming a coating of goethite on the outside. The pyrite of the Sushka village area is associated with marcasite. Sulfur (δ34S ‰) of pyrite is enriched in the light isotope; the isotopic composition varies from -14.21 to -34.86 δ34S ‰, CDT. According to these parameters, pyrite corresponds to the sulfur isotopic composition of ancient sedimentary pyrites from the stage of diagenesis of marine chemogenic sediments. Pyrite from the area of the Novoafonskaya cave cave was enriched in the light sulfur isotope as a result of fractionation during biogenic sulfate reduction at the stage of early sediment diagenesis and subsequently did not undergo epigenetic transformations.

The development of the housing and communal complex is focused on ensuring guaranteed access of the Russian population to high-quality drinking water. Due to the deterioration of drinking water quality, the mineral composition of sediments in the heating and hot water supply systems of the towns of Apatity and Kirovsk (the Murmansk region) has been studied. It has been established that sediments in the heating system mainly consist of iron oxides and oxyhydroxides: magnetite, goethite and lepidocrocite. All these mineral phases are products of active oxidation (corrosion) of steel pipes and heating system equipment. No mineral phases of ferrous forms of iron have been found in the sediment, which indicates sharply oxidizing environment in the heating system. The presence of sulfur-containing mineral phases, namely, anhydrous calcium sulfate - anhydrite and elemental sulfur, has been recorded in the heating system of the Apatity combined heat and power plant. Indirectly, the presence of such sulfur-containing phases may indicate the possible presence of microflora (bacteria) in the heat-transfer agent, in the metabolic processes of which sulfur and sulfur-containing compounds are involved.

Subject. The aim of the work is to study the mechanism and sources of water formation, as well as the peculiarities of carbonate mineralization in the aquifer of the Kyndyg thermal water deposit. Materials and methods. The samples of water (8) and deposited carbonates (15), collected at different seasons at three sites, characterized by different temperatures and distances from the source, were investigated. pH, Eh, and electrical conductivity were determined by an electrochemical method. For the determination of HCO3 – , Cl– , SO4 2–, titrimetric, mercurymetric and turbidimetric methods were used. Trace element composition was determined by ICP-MS (NexION 300S); strontium isotopic composition – by MC-ICP-MS (Neptune Plus) using the bracketing technique after Sr chromatographic separation. Results. The chloride-calcium hydrochemical type prevails in the studied waters. A number of trace elements in water exceeds the clarke concentrations for groundwater in the supergene zone of mountain landscapes. 87Sr/86Sr isotope ratios (0.7065–0.7072) in thermal waters suggest that their composition is determined rather by the isotopic characteristics of the rocks through which water drains than by the influence of sea water. Among the newly formed carbonates, aragonite prevails. In contrast to thermal water, the concentrations of most metals in carbonates are below the clarke values; only Sr and Se are increased, which content is significantly increased in water as well. Deposited carbonates are characterized by 87Sr/86Sr values (0.7028–0.7074), which are lower than in the source thermal waters. Conclusions. On the basis of hydrogeological, hydrochemical and geochemical data, it can be assumed that the waters of this aquifer complex are formed mainly due to fresh fractured karst waters of lower Cretaceous limestones with submerged monocline dipping into the zone of slow circulation and mixing with sedimentogenic sodium chloride waters. The geochemical data and the presence of scandium anomaly suggest that the underlying Jurassic volcanogenic rocks also participate in water exchange.