Subject. The ideas of plume tectonics became active and developing only several years later than the theory of plate tectonics. But in the Urals, the question of plume tectonics, contrary to plate tectonics, was not raised, with rare exceptions, until the latest decade. It is explained by great difficulties in revelation of plumes in any ancient foldbelt, because seismic tomography is not applicable, and magmatic complexes are partly covered by younger sediments, partly eroded, and, additionally, undergone distortion, connected with continental break-ups and drift, subduction and fold-and thrust deformations. Materials and methods. However in recent years, among the magmatic complexes of the Urals (mostly in its western areas), Pay-Khoy and Novaya Zemlya, thanks to precise definition of magmatic formations ages, study of their geodynamically conditioned petrochemistry and their correlation with other regions, the author identified ten levels of probable manifestations of plume/superplume events. Results. It is assumed that in the modern Urals the relics of the following plumes: Navysh (Lower Riphean), Mashak (Middle Riphean), Arsha and Kiryabinka (Terminal Riphean), Mankhambo (Cambrian), Kidryas (Lower-Middle Ordovician, Ushat (Late Ordovician-Lower Silurian), Kola-Dniepr (Devonian), Stepninsk (Permian), Ural-Siberian (Lower-Middle Triassic) had remained.

Introduction. The ground of the rheological Earth’s crust model with a barrier zone between its upper and middle parts is given. The zone is impermeable to fluids radically changes present-day understanding of the upper part lithosphere structure. A critical generalizing review for, earlier models of the continental crust structure and geological nature of K₁ geophysical interface, which proposed by different authors, are is commited for consideration. Metods. The information regarding the middle crust watering is presented. The data on electromagnetic deep probing indicate that in the middle and lower crust and, possibly, in the upper mantle the content of free water makes up about 1% in volume. Therefore, there is some kind of block which does not allow for the whole water to squeezed up into the upper part of the Earth’s crust, where an open crack-pore space is filled with water under hydrostatic pressure. So, clearly expressed hydrodynamic zoning exists in the continental Earth’s crust. This universal continental Earth’s crust zoning now is confirmed by geophysics and super-deep drilling, but it is not yet enough realized by a great number of geologists and geophysicists. Discussion. In the upper crust the rocks become harder with deepening, as the effective pressure increases and stronger and stronger press down them. Geophysical studies mark this fact by the growth speed of seismic wave spreading and the decrease of electrical inductance. Lower of the pores and cracks closing horizon (lower of the barrier) the picture sharply changes. Effective pressure is falling and rocks lose fully their hardening, becoming even less hard than at the day surface. Consequently, lower of the hardest upper crust bottoms under a dense impenetrable zone extremely weakened water-containing rocks are located. The earth crust turns out to be sharply stratified into (zones) not only by the water-presence, but even more contrastingly - by rheological (hardening) properties. At any even miserable mechanical movements and deformations at the boundary of hard and weak storeys disruptions and motions is inevitably occured. Conclusions. The importance of suggested model of the crust structure for the tectonics, petrology, ore-formation, hydrogeology, oil geology, seismicity as well as for the nuclear wastes and others is considered.

Subject. Analysis of lithogeochemical proxies in the Upper Vendian mudstones reveals little if any variation in depositional environment for the Redkinian, Belomorian and Kotlinian regional stages in the east, northeast and north of East European Platform. The coeval macrobiota, in contrast, demonstrates significant macroevolutionary and macroecological transformations. Thus, the Avalon-type ecological association consisting of frondomorphs and vendobionts evolved in low-energy inner shelf during the Redkinian, the Belomorian Stage is characterised by diversification of frondomorphs, migration of vendobionts into relatively high-energy depositional settings (shoreface and prodelta), and emergence of tribrachiomorphs and bilateralomorphs, where as the Kotlinian Stage is marked by a sharp decline in taxonomic diversity of soft-bodied organisms (the Kotlinian Crisis). We don’t know to what degree, if at all, depositional parameters as palaeogeodynamics, palaeoclimate, sediment composition, volcanic activity influenced the Ediacaran biota, but these agents were not responsible for the above mentioned biotic transformations. Materials and methods. We suggest that intrinsic factors such as ecological interactions could be the primary trigger of the Kotlinian crisis. This conclusion has been reached based on the study of composition of major rock-forming oxides, rare- and trace elements in fine-grained aluminosiliciclastic rocks (argillites, shales and silt-rich mudstones). Geological samples were collected in outcrops of the Asha Group of South Urals and Sylvitsa Group of Central Urals, as well as from the drill core of the Keltma-1 (Vychegda Trough) and Tuchkino-1000 (Southeast White Sea area) boreholes. We also used the data on chemical composition of mudstones from the Staraya Russa and Vasil’evsky Ostrov formations form the southern slope of the Baltic Shield. Results. With this information in hand we could assess, with varying degree of confidence, such parameters as a degree of recycling of the material supplied into the late Vendian Mezen Basin; sediment provenance; composition of the substrate that microbial mats and soft-bodied organisms lived on in different parts of the basin; and palaeogeodynamic environment at the time when different groups of soft-bodies organisms were emerging.

The results of lithological and geochemical study of the Hirnantian deposits on the western slope of the Subpolar (Ko-BKB and Ko-108/01 sections) and Northern (BK-2 section) Urals are presented. At the beginning of the Hirnantian the regression in the Timan-northern Ural region on the outer zone of the carbonate platform margin (eastern sections of Ko-BKB - the Bad’yashor Fm in the Kozhym River, Subpolar Urals and BK-2 - pack 1 of the Verkh Ruchej Fm in the Ilych River basin, Northern Urals) was manifested in the formation of breccias, erosion surfaces with pockets, carbon and oxygen isotope excursions. In the inner zone of the platform margin (western section Ko-108/01 - pack 1 of the Yunkoshor Fm) was formed bioclastic sands, erosion processes have been significantly weaker. In the late Hirnantian existed shoals with crinoidal-sand facies (sections Ko-BKB - the Kamennaya Baba Fm and BK-2 - pack 2 of the Verkh Ruchej Fm) and more quiet water conditions of lower intertidal zone (section Ko-108/01 - pack 2 of the Yunkoshor Fm). The difference in the sedimentation was due to the existence of paleouplifts and paleodepressions (raised and lowered blocks of composite basement) on the carbonate platform. The similar environments in the sedimentary basin are revealed in the mid-Hirnantian by the negative excursion of carbon and oxide isotope curves clearly expressed in all sections. This shift reaching in the δ¹⁸О to 4.7‰ fixed in the section Ko-BKB. Such expressive isotope excursion can apply as the regional geochemical marker of the mid-Hirnantian deposits. This time interval characterizes an abrupt shallowing, intense continental runoff, and influence of fresh-water due to short-term extensive regional regression in the Timan-northern Ural marine basin. For the Hirnantian Stage in stratigraphic scheme of the Western Urals on the basis of sections completeness it is necessary to allocate the “Kozhym” Regional Stage with the stratotype sections in the Kozhym River on the Subpolar Urals, which must be located above the Kyr’ya Regional Stage corresponding to the upper Katian.

Object . The results of geochronological and isotope-geochemical studies of the Arsentyevsky titaniferous gabbro-syenite massif of the Western Transbaikalia, which previously referred to the gabbro-syenite series of a two-phase structure are presented. The rocks of the massif contain an increased concentration of titanomagnetite, ilmenite, magnetite and in some cases apatite and are considered as complex iron-titanium ores. Methods. The studies were performed by silicate analysis me­thods, XRF and ICP-MS; age determination for zircons was carried out by LA-ICP-MS and SHRIMP-II methods. The composition of minerals on the X-ray microarray analyzer MAP-3 and electron microscope LEO-1430 was studied. Results. In the basites, a standard trend is observed for the evolution of compositions from melanocratic to terminal leucocratic differen­ces with an increase in the content of silica, alumina, and sodium, and a decrease in magnesium and calcium. Syenites differ from anorthosites in the content of impurity elements including rubidium, niobium, strontium and REE The geochronological studies of rocks of Arsent’evsky gabbro-syenite massif, showed a significant time gap in the formation of gabbroids rela­tive to syenites. The U-Pb age of the gabbroids was 279.5 ± 2.0 Ma, alkali feldspar syenites have age 229.4 ± 2.8 Ma, and biotite syenites - 226 ± 2.4 Ma. Conclusion. The obtained results by age and data on the geochemical features of the rocks made it possible to conclude that there was no genetic relationship between basites and syenites. Petrochemical and geochemical features of biotite and alkali-feldspar syenites proved to be close to the rocks of the Mesozoic Kunaleisky complex.

Object. In the article presents the the results of mineralogy, geochemistry and isotope-chronological investigation of zircons from gabbro Nurali massif. Materials and methods . Amphibole gabbro is the fine-grained and massive texture rock, which cosists of hornblende, the base plagioclase and epidote. The contents of REE in the gabbro significantly exceeds their content in associated ultramafites of the massif. The content of REE and trace elements in zircons was determined by the method of secondary ion mass spectroscopy on the CAMECA-IMS-4F device. U-Pb date of zircons was obtained on the SHRIMP II microprobe. Results. Different variants of complex multiphase zonal structure of gabbro zircons are established. Along with the well known classical fine- and coarse-zonal kinds, a new type of zoning - “polygenic” - is distinguished. It combines the features of both primary growth and superimposed processes. The basis of the material evolution of zircons is progressive process of growth of their refining, reduction of U, Th and REE in later generations. These changes do not go beyond the boundaries of a single geochemical space, due to the connection with a single source. The mechanism of formation of successive zircon generations reflects the anatectic origin of gabbro. The age of zircons from gabbro is 410.5 ± ± 1.1 Ma for the duration of the process of crystallization of rock - 2.0-2.5 Ma. There is on 30-35 million years younger than the zircon from lherzolites of the massif. Conclusion .We consider that this indicates a lack of genetic links between them. The history of the development of gabbro is not associated with the formation of the ultramafic massif.

Object. This study firstly evaluates Hf-isotope characteristics of zircons from wehrlite of the platinum-bearing Feklistov massif, which is closely associated with platinum coastal placer deposits. Materials and methods. In-situ Hf-isotope data were collected on the dated spots within zircon grains using a New Wave LUV213 laser-ablation microprobe attached to a Nu plasma MC-ICP-MS. Resuts. Significant variations of¹⁷⁶Hf/¹⁷⁷Hf_i (0.28241-0.28312) and εHf(t) (from -4.8 ± 1.1 to 20.3 ± 0.6) in Paleozoic zircons indicates interaction of a ‘juvenile’ mantle source (εHf(t) ≈ 15) with distinct magma sour­ces, possibly equivalent to a subcontinental lithospheric mantle and/or a continental crust (εHf(t)от -5 до +5). Proterozoic and Late Archean zircons from the Feklistov massif are characterized by less pronounced¹⁷⁶Hf/¹⁷⁷Hf_i (0.28107-0.28224) and εHf(t) (from -4.8 ± 0.4 to 8.1 ± 0.6). Conclusion . Hf-isotope features for majority of Precambrian zircons from the Feklistov massif (εHf(t)from -3.8 ± 0.5 to +2 ± 0.5) are consistent with their xenogenic nature and inheritance from basement rocks of the Siberian Craton.

Object. The article describes a new geological and geochemical data for Permian host rocks and copper sandstones (CS) in Orenburg’s Pre-Urals. Methods . X-ray fluorescence, atomic absorption for Au and Ag, and ICP-MS analysis were used during investigations. Results. The cupriferous sandstones are enriched in a quite broad range of microelements: Cu, Ag, Au, Cd, Сr, Ni, Mn, Co, V, U, Sc, and Pb, compared to the average values of the upper crust. The Co/Ni ratio in the CS is very low, which is typical of low-thermal fluids of meteoric origin. The CS are characterized by a REE spectrum without Eu-minima and maxima, which is close to the chondrite spectrum. Like in the host rocks, the “cerium” group of REE dominates in the CS over the “yttrium” and “scandium” groups. The spectra of REE of the CS and the host rocks have definitely similar morphology. The δCe and δEu combination indicates that CS was formed under oxidizing conditions. On geological and genetic characteristics and geochemical indicators installed the similarity of the CS in the southern Pre-Urals deposits and the Manto-type Cu-Ag deposits of Chile and Iran, and also with the CS of Iran and Cu-shales of Kupferschiefer. Conclusion. Proposed geological-genetic model of CS, points to possible high rise development of the Cu-Ag mineralization at depth as in the fields of the Manto-type copper deposits in Chile and Iran. Geochemical data show that accommodating the Permian strata could serve as a source of REE and other trace elements for ore-forming fluids. Perm CS of Pre Urals can be considered as a very promising new (“old”) source of raw materials for the development of the copper industry of the region. The obtained results can be used to predict new ore fields in the Eastern Russia region.

Object. The article considers the results of geochemical studies of ore-bearing effusive and intrusive rocks of the Nikolaevka gold deposit, located in the zone of the Main Uralian fault in the Southern Urals. The deposit belongs to the gold-porphyry type which unconventional for the Urals and poorly studied here. Methods. The rock composition was determined by chemical analysis (IG UFRC RAS), mass-spectrometry with inductively coupled plasma on the ELAH 9000 quadrupole mass-spectrometer (IGG UB RAS) and X-ray fluorescence analysis on the VRA 30 spectrometer (IG UFRC RAS). Results. It is established that gold-porphyry mineralization associated with an island-arc volcanic-intrusive complex that unites plagiophyric and pyroxene-plagiophyric basalts, their tuffs, gabbro intrusions and ore-bearing series of dikes plagiophyric dolerite-porphyrites and gabbro-diorite-porphyrites. The rocks of the complex, including ore-bearing dikes, have normal alkalinity, tholeitic and transition from tholeitic to calc-alkaline composition. Among the volcanogenic formations, faunistically dated in the zone of the Main Ural fault in the Southern Urals, by a number of geochemical parameters (for example, the ratios of Zr/Nb and Nb/Th) the effusive and intrusive rocks of the deposit are the closest to the volcanics of the pyrite-bearing Baymak-Buribay Formation (D₁e₂), lying at the base of the section of the Magnitogorsk island arc, and, in all probability, are their age analog. At the same time, the gold-bearing complex differs from the Baymak-Buribay Formation by a general increased iron and titanium content, with a reduced magnesia of all rock types, as well as the absence of boninites and acid volcanics, the predominance of porphyry rock types, which can be due to the geodynamic conditions of its formation. Conclusion. Geodynamic analysis of geochemical data using diagrams (La/Sm)N-TiO₂ and V-Ti/1000 suggests that the Nikolaevka deposit was formed in the articulation zone of the island arc and the back-arc basin. Gold-porphyry mineralization associated with the Late Emsian volcanic processes was isolated in the Southern Urals for the first time.

Object . The zonal pyrite nodules and metacrystals from siliceous siltstones of ore-bearing horizon of the Second ore body from the Yubileynoe massive sulfide deposit are studied. Materials and methods . We used 9 samples and 15 polished sections of siliceous siltstones with pyrite mineralization. Analysis of chemical composition minerals was determined by Tescan Vega 3 with an energy dispersive microprobe Oxford Instruments X-act (Institute of Mineralogy UB RAS, Miass). Quantitave LA-ICP-MS analysis of pyrite for major and trace elements was carried out using New Wave Research UP-213 laser microprobe coupled to an Agilent 7500 quadrupole ICP-MS housed (University of Tasmania, Australia). Results. Microtopochemistry was established that the diagenetic core of the nodule is characterized by trace elements of typical poikilites of quartz (Si) and alumosilicates (Si, Al, Mg, V, Cr, K, Na, Ca), rutile and titanite (Ti), inclusions of chalcopyrite (Cu), sphalerite (Zn), galena (Pb, Sb, Bi), tetrahedrite-tennantite (As, Sb), native gold, petzite, hessite (Au, Ag, Te), tellurobismuthite, altaite, and coloradoite (Te, Bi, Pb). Cobalt and Ni substitute for Fe²⁺. The rim of subhedral pyrite is depleted in most trace elements except for Ni and As. Subhedral pyrite became rich in chalcophile (Au, Ag, Sb, Bi, Cu, Zn, Hg) and lithophile (Ca, K, Na, Cr) elements at the final stage of growth of the nodule. Similar mineralogical and geochemical zonation is typical of the pyrite metacrystals, where a micro-grained core concentrates Pb, Bi and Te, and a rim of subhedral pyrite is depleted in most trace elements. Similarly to the nodules, the outer rim of pyrite metacrystals is enriched in most trace elements (Pb, Au, Ag, Sb, Cu, As, Mo, Cr, etc.). The nodules and metacrystals were formed from diagenetic micronodule of poikilite pyrite. Conclusions. It is suggested that mineralogical and geochemical differences in pyrite metacrystals and nodules are caused by the greater degree of development of rims of subhedral pyrite.