The study of granites in the basement of the Western Siberian platform is highly relevant since they are associated with hydrocarbon deposits, which are located not only above the granite massif, but also within the metasomatically altered upper layer of granites. At the same time, granites are most easily and reliably dated by zircon, which makes the geological structure of the area easier to examine, especially when the latter is overlapped by a thick sedimentary cover. The composition of granitoids from the basement of the Traigorod–Kondakovskii licensed site of the Western Siberian megabasin, located in the northwestern part of Tomsk Region, near the border with the Khanty-Mansi Autonomous Okrug, about 40 km east of the village of Aleksandrovskoye, has been studied. This license area is located within the Aleksandrovskii arch, which is bounded by the Ust-Tymsk Depression in the southeast and the Koltogorskii Trough in the northwest. The Aleksandrovskii Arch has a complex structure, which includes the large Krivolutskii granite batholith enclosed in the Carboniferous–Devonian sedimentary (mainly carbonate) rocks and Ordovician–Silurian shales. It has been established that batholith rocks are leucogranites and granites of normal alkalinity and have undergone metasomatic alterations in the form of propylitization and argillization. Granites belong to the I-type and were probably formed from the island arc substrate. Their age, according to the results of U–Pb zircon dating, is approximately 268 Ma; i.e., the generation and intrusion of granites took place during the beginning of the formation of the Koltogorsk–Urengoi Rift, the central rift of Western Siberia (which, according to Ar–Ar basalt dating, was also formed 268 million years ago).

The article covers the U-Pb dating of minerals belonging to the pyrochlore group from the rare-metal ore deposits of Ilmeny-Vishnevogorsky carbonatite-miaskite complex (South Urals). Individual pyrochlore crystals were dated through a new technique of in-situ U-Pb dating using SHRIMP-II, which was developed at VSEGEI (St.Petersburg). The U-Pb dating of high-uranium pyrochlore (more than 2.5 wt % UO2) was carried out employing laser ablation and ICP-MS. The U-Pb systems of studied pyrochlore samples indicate a multi-stage formation of rare-metal niobium mineralisation. The earliest age of ore formation (378 ± 4.9 ma) is yielded by the U-Pb systems of U-bearing pyrochlores from the carbonatites of the Potanino deposit. This period of ore formation is probably associated with the final stages in the crystallisation of the alkaline-carbonatite magmatic system. The next periods of ore formation (230 ± 1.5 Ma) are widely manifested in the Vishnevogorsky and later in the Potanino deposit (217.2 ± 1.9 Ma), which is probably associated with the remobilisation and redeposition of alkaline-carbonatite and rare-metal substances at the post-collision stage in the evolution of Ural carbonatite complexes.

Research subject. This article is devoted to the formation features of the Ural-Timan-Paleo-Asian segment of Eurasia. Materials and methods. The research was based on the authors’ data and those obtained following a review of available publications on the geology of segmentation. The Timan region was investigated using the geological information obtained by V.G. Olovyanishnikov.Results. A geodynamic map of the Ural-Timan-Paleo-Asian segment with a scale of 1 : 2 500 000 was compiled, which allowed further research into the structure and formation of the north-western part of the Eurasian area. This part was found to be mostly composed of geodynamic associations of orogens, orogenic systems and orogenic belts of the Upper Proterozoic (Riphean) and Paleozoic time intervals, as well as by elements of the Mesozoic-Cenozoic neoplate. These processes were supplemented by the formation of tectonic systems of superimposed depressions and protoplate protrusions. The formation of orogens, orogenic systems and orogenic belts is associated with the development and subsequent transformation of paleooceanic basins under the conditions of accretion and collision. The terranes of the ancient continental crust also participated in the formation of the segment’s geodynamic elements, for which a typification scheme was proposed. The articles present new data on the formation conditions of the segment’s orogenic elements and the relationship of the orogeny with global reconstructions, including the problem of closing the surrounding oceanic space.

Research subject. In this research, we carried out Sm-Nd- и Rb-Sr-dating of pyrochlore carbonatite from the Vishnevogorsky niobium deposit, Ilmeno-Vishnevogorsky Alkaline Complex, Southern Urals. IVC is located in the Ural fold region and is a carbonatite complex of the linear type. Rare metal (Nb-Zr-TR) deposits and occurrences are related to IVC. The age and the duration of IVC deposits formation remains a matter of debate. To determine the age of IVC carbonatites and related niobium ore, we measured Sm-Nd and Rb-Sr isotopic compositions and concentrations of the elements in the minerals (pyrochlore, calcite, apatite, biotite) and bulk sample of pyrochlore carbonatite. Materials and methods. The Sm and Nd isotopic compositions and concentrations were determined on a Finnigan MAT-262L (RPQ) seven-collector mass spectrometer in the static regime at the Geological Institute of the Kola Scientific Center, Apatity, Russia. The Sr and Rb isotopic compositions and concentrations were determined on thermos-ionization mass spectrometer Triton Plus (“Geoanalitik”, IGG UD RAN, Ekaterinburg, Russia). Results. Age of pyrochlore carbonatites from ore zone 140 (Vishnevogorsky deposit, IVC) defined by Sm-Nd and Rb-Sr isotopic methods. Mineral Sm-Nd-isochron (5 points) indicated age 229 ± 16 Ma, mineral Rb-Sr-isochron (5 points) showed similar age 250.5 ± 1.2 Ma. Conclusions. Results Sm-Nd и Rb-Sr dating indicate that the pyrochlore сarbonatites of ore zone 140 crystallized ≈ 250 Ma ago, at the stage of the postcollisional extension, possibly, in connection with exhumation complex, which was accompanied by decompression, partial melting of rocks, involving fluids, dissolution and precipitation of Ordovician-Silurian alkaline-carbonatitе complex. Thus, the formation of the IVC carbonatites and related Nb-ore, which began in Silurian (S), continued in Permian (P) and Triassic (T1-2) and was associated with the post-collision stage of tectonic activity in the Ural Fold Belt.

A clinoenstatite rim occurs in many refractory forsterite-rich objects; however, specialized studies of it have not been carried out. The first data from the study of refractory forsterite-rich objects by electron backscatter diffraction (EBSD) are reported. It is shown that the clinoenstatite rim in refractory forsterite-rich inclusions has a reactionary nature and was formed as a result of nebular processes. The rim is almost entirely composed of clinoenstatite. Forsterite grains have a block internal structure with a maximum misorientation angle of 10° within a single crystal.

The 40Ar/39Ar dating of metamorphic schists from the basement of the West Siberian Platform exposed by Lenzitskaya well no. 77 on the Taz Peninsula was performed. The samples collected at depths of 3503 and 3515 m yielded age dates of 251.6 ± 3.5 and 271.2 ± 3.5 Ma. The age of ~271 Ma reflects the age of metamorphism of schists, which was induced by a strong tectonomagmatic event, associated with the onset of emplacement of rift zones and outflow of basalts in the Permian–Triassic. The age of ~252 Ma coincides with the period of the most intense emplacement of submeridional rifts in the basement of the West Siberian Platform. This process was accompanied by extension and thinning of the Earth’s crust in this region, which resulted in the exhumation of rocks from the mid-crystal level. The age boundary of ~250 Ma was established in the metamorphic and intrusive complexes of western Siberia and the Urals. This age is fixed almost everywhere and is correlated with the age of formation of the Siberian Trap Province.

Fluorcalciobritholite and fluorbritholite-(Ce)-rare-earth minerals from the apatite supergroup-have been found in the course of the study in monzogabbro from the pre-Jurassic foundation of the Novoportovskoye oil and gas exploration area (southern part of the Yamal Peninsula). They form short-prismatic small individuals around fluorapatite crystals and belong to the primary mineral (magmatic) assemblage. This first finding of these minerals in gabbroids significantly expands our understanding of their occurrence in the nature.

This paper reports on the first U–Pb dating of zircons from dacites of the volcanic paleo-edifice of the andesite–dacite complex of the Eastern Zone of the Middle Urals orogen. The Eastern Zone involves the retroshariage and sheet-folded structural subzones. The volcanic complex, which includes vent and peri-vent facies, lies in the sheet-folded subzone among flyshoid and carbonate deposits with Middle Devonian fauna. This subzone forms the easternmost border of the orogen. The age of zircon grains is 389 ± 5.6 Ma, which is also in accordance with the Middle Devonian. Therefore, the sedimentary and volcanic complexes were formed around the same time, but based on their composition and structure, in different facial conditions. The sedimentary deposits were accumulated in shallow basins; the volcanic deposits were likely formed in the subaerial conditions surrounded by a shallow sea basin. We suppose that the manifestation of andesite–dacite volcanism in association with the sediments of shallow basins most likely points to the spatial and age-related displacement of the geodynamic and facial conditions of volcanism to the eastern periphery of the orogen.

The amount of hydrocarbon deposits per unit area of Yamal Peninsula is more than 100 times as much as the global average. The hydrocarbon deposits are generally situated in areas with high current geodynamic activity. According to the data of seismic tomography, in the Yamal area, the mantle structure is abnormal. The southern part of the Kara Sea, the Yamal Peninsula, and the western part of the Gydan Peninsula are involved into the large positive anomaly of the heat flow density, the epicenter of which occurs in the vicinity of the Rusanovskoye deposit. Almost all hydrocarbon deposits of Yamal are situated on the flanks of the West Siberian rift system and, simultaneously, in the gradient zones of the heat flow density.

Концентрация месторождений углеводородов на единицу площади на Ямале более чем в 100 раз превышает среднемировую. Месторождения углеводородов обычно располагаются в районах с высокой современной геодинамической активностью. Структура мантии в районе Ямала по данным сейсмической томографии имеет аномальные черты. Южная часть Карского моря, Ямал и западная часть полуострова Гыдан лежат в области большой положительной аномалии плотности теплового потока с эпицентром вблизи месторождения Русановское. Практически все месторождения углеводородов Ямала расположены на флангах Западно-Сибирской рифтовой системы и одновременно в градиентных зонах плотности теплового потока.

New data on the material composition of the Severny Kolchim meteorite, found in the Perm region territory in 1965, is presented. It is established that the cosmic substance is composed of forsterite, enstatite, diopside, plagioclase (oligoclase, bitovnite), glass, chromite, magnetite, ilmenite, rutile, iron and nickel metals (kamasite, taenite and tetrataenite), sulphides (troilite, pentlandite), chlorapatite and merrillite. Some minerals, namely the diopside, tetrataenite, chlorapatite and merrillite, were determined in the Severny Kolchim meteorite first time. The data on the chemical composition of minerals and the trace element composition are given. It was verified that this meteorite is a nonequilibrium stone chondrite and belongs to the petrological type H3.

Приводятся результаты впервые выполненного U-Pb-датирования цирконов из дацитов вулканической палеопостройки андезит-дацитового комплекса Восточной зоны среднеуральской части Уральского орогена, состоящей из ретрошарьяжной и покровно-складчатой структурных подзон. Вулканогенный комплекс, включающий жерловые и прижерловые фации, залегает среди флишоидных и карбонатных отложений с фауной среднего девона в покровно-складчатой структурной подзоне, образующей крайнее восточное ограничение орогена. Возраст зёрен циркона составил 389 ± 5,6 млн лет, что также отвечает среднему девону. Следовательно, формирование осадочного и вулканогенного комплексов происходило в близком возрастном интервале, но, судя по их составу и строению, в разных фациальных условиях. Осадочные образования накапливались в мелководных бассейнах, а вулканические формировались, по-видимому, в субаэральных условиях в окружении мелководного морского бассейна. Предполагается, что проявление андезит-дацитового вулканизма в ассоциации с осадками мелководных бассейнов, скорее всего, свидетельствует о пространственном и возрастном смещении к восточной периферии орогена геодинамических и фациальных условий вулканизма.

Проведено U-Pb датирование минералов группы пирохлора из редкометалльных месторождений ильмено-вишневогорского комплекса Южного Урала. Для измерения возраста отдельных кристаллов пирохлора была использована новая методика локального U-Pb датирования на вторично-ионном масс-спектрометре SHRIMP-II, разработанная в ЦИИ ВСЕГЕИ (г. Санкт-Петербург). U-Pb датирование высокоурановых пирохлоров (с содержанием окислов урана более чем 2.5 мас. %) проводилось с помощью лазерной абляции и масс-спектрометра с ИСП-МС (DUV-19 и LA-ICP MS). U-Pb система изученных образцов пирохлора свидетельствует о многоэтапном формировании редкометалльной ниобиевой минерализации ильмено-вишневогорского комплекса. Наиболее древний возраст (378 ± 4.9 млн лет) фиксируется изотопными U-Pb системами уранпирохлоров ранних карбонатитов Потанинского месторождения. Этот этап рудообразования, возможно, отражает завершающие стадии кристаллизации щелочно-карбонатитовой магматической системы. Следующие этапы рудообразования широко проявлены на Вишневогорском (230 ± 1.5 млн лет) и позднее на Потанинском (217.2 ± 1.9 млн лет) месторождениях и, вероятно, связаны с ремобилизацией и переотложением щелочно-карбонатитового и редкометалльного вещества на постколлизионном этапе эволюции карбонатитовых комплексов Урала.

The heterogeneous assemblage of zircons was identified in metamorphic schists of the Karabash site of the West Siberian Plate. Based on the U–Pb (SHRIMP II) isotope data, zircon varies in age from the Archean–Paleoproterozoic boundary to the early Permian. The Precambrian age data obtained for the study area reflect the erosion of the Precambrian complexes in the framework of West Siberian Plate (with subsequent redeposition of the ancient detrital material within the West Siberian megabasin). Our results make it possible to clarify the history of the formation and evolution of metamorphic rocks in the basement of the West Siberian Plate.