Relevance of the research is caused by the need of detailed petrological studies of numerous potentially mineralized mafic-ultramafic massifs of the Kan block of the Eastern Sayan to improve the correlation of regional schemes, and to identify in them Pt-Cu-Ni mineralization. The main aim of the study is to proof the substantial similarity of Talazhinsky and Argysuksky massifs and their possible inclusion in a single formational type. The methods used in the study: petrographic characteristics on the polarizing microscope AxioScope Carl Zeiss, petrochemical composition of rocks by RFA, and rare earth elements by ICP-MS, the chemical composition of minerals on the scanning electron microscope Tescan Vega II XMU, equipped with energy-dispersive spectrometry (with a semiconductor Si (Li) detector INCA x-sight) INCA Energy 450 and wave-dispersive spectrometer INCA Wave 700. The results. The authors have studied the petrological and geochemical features of Talazhinsky and Argysuksky massifs of the Kansk block of the Eastern Sayan and revealed their high similarity. They admit that further detailed studies of these objects allow combining them into a single formation complex when improving regional schemes of correlation. It was assumed that both massifs are a unified intrusive body, which was formed under the conditions of the island arc from original high-alumina olivine-basalt melt. The emergence of foci of the initial melt occurred from tholeiitic basalts of oceanic plateau at their melting in the subduction zone. The subsequent evolution of the melt is conditioned by its movement in the earth's crust, accompanied by contamination of the host rocks. Stratification of intrusion, is obviously caused by magmatic crystallization and differentiation in the magma chamber. Both massifs are classified as promising objects for identifying copper-nickel mineralization.