We provide the results of studying the internal structure and composition of the rocks of the Semeitau and Delbegetei massifs located in Eastern Kazakhstan. It was previously believed that these massifs have different ages and were formed in different geodynamic settings. The U-Pb zircon age from the monzonites and quartz monzonites was determined to be 249 ± 2 Ma, which showed the same Early Triassic age of the massifs. Both massifs are composed of rocks of the same monzonite–granite series of rocks with a significant proportion of high-silica rocks (leucocratic granites). Intermediate rocks are formed due to the differentiation of subalkaline mafic magmas, and the felsic rocks (rhyolites and granites) are the result of partial melting of crustal substrates. The massif formation model assumes the intrusion of mafic magmas into the crust, their differentiation and mixing with crustal melts, and then the intrusion of various rocks into the upper crustal levels. Analysis of the geological position, age and composition of the rocks allows us to conclude that the Semeitau and Delbegetei massifs were formed in an intraplate geodynamic setting. The activity of the mantle plume is the most probable reason for their formation. The Semeitau and Delbegetei massifs can be included in the southern part of the range of the Early Triassic Siberian Large Igneous Province.

ГЕОХРОНОЛОГИЯ МЕТАМОРФИЧЕСКИХ ПОРОД КУРАЙСКОГО АККРЕЦИОННОГО КЛИНА (ЮГО-ВОСТОЧНАЯ ЧАСТЬ ГОРНОГО АЛТАЯ)

This study presents the results of an integrated petrographic and U-Pb geochronological investigation of Lower to Middle Carboniferous sandstones from the Volga-Ural petroleum province. The samples were obtained from drill cores collected in the South Tatar Arch and the northeastern flank of the Melekess Depression. The combined data reveal distinct provenance signatures for the Lower and Middle Carboniferous units. The Lower Carboniferous sandstones are characterized by a monomictic composition, dominated by well-rounded quartz grains. The heavy mineral assemblage consists primarily of ultra-stable minerals such as rutile, anatase, and zircon. U-Pb (LA-ICP-MS) dating of detrital zircons indicates a dominant Proterozoic age population, suggesting source areas associated with the Sveconorwegian and Svecofenian orogenic belts. In contrast, the Middle Carboniferous sandstones display a polymictic composition, comprising quartz, feldspar, and lithic fragments with moderate grain rounding. The heavy mineral suite is more diverse and includes both stable (rutile, anatase, zircon, spinel, garnet) and less stable minerals (biotite, amphibole, epidote). U-Pb geochronology reveals a dominant Paleozoic detrital zircon population, pointing to the Uralian orogen as the primary sediment source.

This paper presents new data on the age of the Mastodonsaurus tetrapod fauna (Middle Triassic) of the East European Platform. The analysis of the section a

This article presents the first data on U–Pb LA-ICP-MS radioisotope dating of the Mastodonsaurus tetrapod fauna (Middle Triassic). The radioisotope a

The radioisotopic dating of five stratigraphic levels within the Permian succession of the Kuznetsk Coal Basin refined the ages of the corresponding stratigraphic units and, for the first time, enabled their direct correlation with the International Chronostratigraphic Chart, 2024. The analysis revealed significant discrepancies between the updated ages and the previously accepted regional scheme (1982–1996). A comparison of regional stratigraphic units’ durations with estimated coal and siliciclastic sediment accumulation rates indicated that the early Permian contains the most prolonged stratigraphic hiatuses. The updated stratigraphic framework enabled re-evaluating the temporal sequence of regional sedimentological, volcano–tectonic and biotic events, allowing for more accurate comparison with the global record. Palaeoclimate reconstructions indicated that during the early Permian, the Kuznetsk Basin was characterised by a relatively warm, humid, and aseasonal climate, consistent with its mid-latitude position during the Late Palaeozoic Ice Age. In contrast, the middle-to-late Permian shows a transition to a temperate, moderately humid climate with pronounced seasonality, differing from the warmhouse conditions of low-latitude palaeoequatorial regions. The latest Lopingian reveals a distinct trend toward increasing dryness, consistent with global palaeoclimate signals associated with the end-Permian crisis.