Vol 73, No 4 (2018)

Volcanogenic massive sulfide deposits contain not only Cu, Zn, and Pb, but Sb, Bi, Te, Se Ag, Co, other metals, and variable amounts of Ag and Au. In some of these, gold reserves exceed 100 t, while the gold grade reaches several dozens ppm. An original database was used to establish statistically meaningful criteria for identification of deposits with large gold reserves and/or that are anomalously enriched in gold. Some peculiar features of deposits with high Au grades were investigated, including their distribution in geological history and among the principal metallogenic provinces, as well as association with volcanogenic formations and paleovolcanic structures, geochemical and mineralogical features, and factors that caused enrichment in gold.

The composition and origin of the Callovian–Oxfordian deposits of the Sudak Bay were characterized on the basis of the generalization and analysis of our own results, as well as published and unpublished data. The botanical future was first implemented for the geological mapping of the Oxfordian deposits.

The water ecosystem of the Vyshny Volochek Reservoir is characterized based on the study of the distribution of heavy metals speciations in the solid phase and pore waters of bottom sediments. Using the sequential extraction procedure, it is shown that Mn is mainly present in exchangeable and carbonate-bound forms; significant roles for Fe, Zn, Pb, and Co are played by forms that are bound to iron and manganese hydroxides and Cu and Ni are mainly bound to organic matter. Thermodynamic calculations have established the prevailing share of the following forms in pore waters: free ions for Zn, Ni, Co, and Cd, carbonate complexes for Pb, and fulvic complexes for Cu. It has been revealed that the speciation forms of heavy metals in bottom sediments depend on the lithological features and content of organic matter in sediments.

The ore mineralogy of the largest quartz vein, Osinovaya, at the Kedrovskoe gold deposit has been studied. Three stages of mineral formation, namely, marcasite–pyrrhotite–pyrite, gold–polysulfide, and hypergenic stages are identified. Native gold is attributed to the gold–polysulfide stage and is represented by two generations. The earlier high fineness generation (600–870, 780–820 prevails) cements the fragments of pyrite grains or forms inclusions in pyrite, and the later low fineness generation (520–580, 540–580 prevails) is associated with sphalerite–chalcopyrite–galena veinlets in pyrite. The disappearance of arsenious pyrite, the increase in iron content of sphalerite, and the change in pyrite to pyrrhotite with depth is recorded.