The paper presents the results of geological, geochemical and isotope geochronological studies of Early-Middle Devonian volcanogenic-sedimentary strata of the NW Rudny Altai, which host Devonian VMS-type (volcanogenic massive sulphide) deposits. The study provides a solution to the problems of identification and correlation of volcanic formations, study of their structural and lithological-facial features, which is traditionally a necessary element in the reconstruction of ore-magmatic systems. The aim of the study is to reconstruct the volcanic sequence in the Early-Middle Devonian and to evaluate the contribution of volcanogenic formations of riftogenic and supra-subduction nature to which VMS-type deposits are genetically related. Isotopic U-Pb dating of zircons from representative tuffs is consistent with an age of ~390 Ma. The formation of the volcanogenic strata occurred in a tectonic setting associated with the opening of the sea basin, corresponding to the initial stage of riftogenesis in the Rudny Altai. In terms of geochemical characteristics, the rocks of the lower section are similar to those of the ensialic arcs. The petrogenesis of such magmas should be associated with fluid-saturated conditions of partial melting of crustal substrates and under the control of dehydration of the subducting plate. In the upper section, the volcanic rocks are geochemically similar to bimodal formations from riftogenic settings behind the ensialic arc. This is confirmed by analyses of the genetic type of the formation community (magmatic, sedimentary and ore-bearing) and is consistent with the geochemical type of the volcanic rocks, which is similar to that of riftogenic settings. The conceptual geodynamic scenario corresponds to the formation of the Rudny Altai ore deposits in the transition zone between the island-arc and the back-arc basin, similar to the riftogenic settings of the Eastern Asian margin.

A unique Mn-, Cd-bearing sphalerite from quartz-calcite veins in the coal-bearing series (Visean C1v) marine sediments in a 50 km segment of the middle course of the Silova-Yakha River in the Arctic zone of the European part of Russia (Pai-Khoi Ridge) has been studied. The veins have a conformable and cross-cutting occurrence in two types of rocks: gray limestones and black siliceous-carbonaceous shales, the area is known as the Goniatite occurrence. The sulfide content in vein samples ranges from 0.1 to 2 vol.%. The chemical composition of 27 monomineral samples of Mn-, Cd-bearing sphalerites was studied, 82 points were analyzed. Correlations between typomorphic elements-impurities were revealed and correlation matrix was constructed. Cu, V, Ga, In, Sn, As, Sb, Bi, Pb, Tl, Se, Ag, Au, Ni are positively correlated with each other; Cd, Mn and Ge are negatively correlated with each other. The hydrothermal fluid involved in crystallization of sphalerite is characterized by low temperature (164-211 °С) and average salinity of 5-6 wt.% eq. NaCl. An updated “portrait” of typomorphic features (composition and properties) of sphalerite of the Pai-Khoi province was obtained. The features allowing to determine the type of impurity entering the sphalerite structure – in the form of isomorphic impurity or in the form of microinclusions of paragenetic association minerals – have been established. Submicron inclusions of sulvanite and colusite, invisible by other methods, were detected in sphalerite (by LA-ICP-MS method).The cathodoluminescence data of sphalerite from the Pai-Khoi province were typified. In contrast to other provinces, ZnS crystals here are characterized by almost complete absence of isomorphic iron. This allowed us to study pure isomorphism schemes of ZnS↔MnS, ZnS↔CdS, namely cathodoluminescence and other types of luminescence. The presence of a rare wurtzite-4H polytype in assemblage with sphalerite was revealed. High contents of strategic metals Cd, Ga, In, Ge in the ZnS matrix, as well as sulvanite (V, Cu) in a single paragenesis were found. A serious reassessment of the potential for industrial use of this mineralization will be required.