For the first time in podiform chromitites, a mineral of the humite group, titanium–containing hydroxylclinohumite, belonging to natural dense water-containing magnesian silicates (DHMS phases), was found. The find was made in chrome ores of the Paity plateau, located in the northern part of the Voikaro-Synyinsky ultramafic massif of the Polar Urals. Chromitites are deposited in the dunite body, which is located at the contact of apoharzburgite amphibole-olivine-antigorite and amphibole-enstatite-olivine metamorphic rocks containing relics of non-serpentinized harzburgites. According to optical data and chemical composition, the mineral belongs to titanium-containing hydroxylclinohumite, since it contains TiO2 (up to 5.64 wt.%), in the complete absence of fluoride. The presence of OH-grouping in the mineral is confirmed by the Raman spectrum, which generally corresponds to the standard of hydroxylclinohumite. The results of geothermometry show that this mineral was formed in chromitites of the Polar Urals at a temperature of 668–740º with and, probably, a pressure of 20–25 kbar. It follows from this that the formation (or recrystallization) of chromite ores occurred under high-pressure conditions, i. e. ore occurrences of chromites in the northern part of the Voikaro-Synyinsky massif were formed, apparently, in a suprasubduction environment.

Dating of zircons from eclogites and amphibolite in metamorphic rocks of the Eastern Mugodzhar zone (terminal south of the Urals) is conducted. Of four eclogite samples, close (and the oldest ones of 520 ± 4 Ma) concordant age values are obtained in three samples, and these ages probably correspond to the age of the protolith. Concordant dates of 472 ± 3 and 379 ± 3 Ma correspond to the main stages of metamorphism in the East Mugodzhar Range: the former marks the time of high-pressure metamorphism, whereas the latter corresponds to the metamorphism of amphibolite facies. The presence of ancient and at the same time varied-age zircons (probably carrying rounding signatures) indicates the primary sedimentary nature of the amphibolites studied. The youngest zircons from eclogites of the Mugodzhar Range are of 282 ± 2 Ma in age, corresponding to the stage of collision. The obtained data show that the metamorphic complexes of the Mugodzhar Range are not units of Early Proterozoic or Riphean age (as was previously believed), but represent Lower–Middle Paleozoic complexes from the middle of the Earth’s crust. Thus, these metamorphic rocks belong to the deep part of an island-arc system that had been located in the eastern sector of the Urals, which later was drawn to the near-surface level when some regions of the Urals underwent uplift and erosion.

Composition and age of unserpentinized harzburgites found as boudins and relict bodies in the Voikar–Synya massif in the olivine–antigorite fields have been studied. Rock and mineral structure and composition, as well as REE distribution and Sm–Nd absolute dating (≈2330 Ma) make it possible to consider these unserpentinized harzburgites as mantle fragments and the earliest ultramafic rocks of the Voikar–Synya massif. Silicates of these harzburgites are characterized by higher chromium which turns into chrome spinellide in different subsequent processes. Based on the data obtained, the resources of chromium mobilized during the transformation of primary ultramafic rocks have been evaluated.

Natural studies of the South Urals hydromineral deposits, as well as the results of study of the ion and gaseous composition of underground waters, show that the liquid run-off from massive sulfide deposits of the region are promising serious deposits of secondary raw materials. The dump waters are mineral resources for rare metals, the contents of which are comparable with the average content of ores.

The first results of 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic–geochronological results of a comparative study of 12 samples of volcanic rocks of the Bashkirian Meganticlinorium, which were previously dated by zircons from these samples using the U‒Pb SHRIMP-II method showing the predominance of the Paleozoic ages among three stratigraphic levels with Riphean magmatic events in the South Urals, are presented. New 147Sm‒143Nd and Rb‒Sr ID-TIMS isotopic data showed that the volcanic rocks evolved as a result of crustal–mantle interaction. The Nd model ages (TDM) (2302–2540 Ma) of volcanic rocks of the Taratash Anticlinorium represent the ages of the protolith characterized by εNd(t) values from –17.4 to –20.5. The TDM value (2033 Ma) of the Paleozoic volcanic rocks of the Yamantau Anticlinorium indicates a younger (Paleoproterozoic) substrate. The minimum Nd model ages (TDM = 1160–1233 Ma) are determined for the volcanic rocks, which are spatially related to metabasalts of the Igonin magmatic event (707‒732 Ma) in the Tirlyan Syncline. The smallest εNd(t) values (–3.2, –0.9, –0.7) indicating a decrease in the amount of a crustal component relative to the mantle material are determined for the Paleozoic metabasalts in the Tirlyan Syncline in the eastern wing of the Bashkirian Meganticlinorium, which is probably related to the activation of plume processes in the eastern part of the orogen. The Rb‒Sr and 147Sm‒143Nd ID-TIMS isotopic systematics of the studied volcanic rocks expands our understanding of mantle–crustal interactions within three stratigraphic levels with Riphean magmatic events of the South Urals.

Research subject. The deposits of the Uk Formation of the Upper Riphean (Karatavian) in the Alatau anticlinorium (Southern Urals) were studied in the section of the right bank of Basu river and its tribute Manaysu located to the east of the Kulmas settlement.Results. The structure of the sections of Uk Formation along Basu River (Kulmas) in the Alatau anticlinorium and its stratotype at the Yuryzan river near town of Ust-Katav in the Suleimanovo anticline is identical: the Lower Uk Subformation is represented by irregular alternation of sandstones, siltstones and shales with rare layers of limestones and dolomites with Patomella kelleri Raaben and Tungussia bassa Kryl. stromatolites and microphytolites of the IV complex, while the Upper Uk – by limestones with Linella ukka Kryl. and Linella simica Kryl. stromatolites and microphytolites of the IV complex. However, the sandstones and siltstones of the Lower Uk Subformation in the stratotype at the Yuryuzan river (Ust-Katav) are polymictic, while in the reference section along Basu river (Kulmas) they have mostly quartz composition. These petrographic features may be a result of different provenance. In the rocks of Uk Formation in the Basu section (Kulmas), the epigenetic processes (dolomitization and silicification) are strongly manifested. In the limestones of the Upper Uk Formation the caverns and fractures along with layers enriched by a bitumen (?) are observed.Conclusions. The reference section of the Uk Formation along the river Basu (Kulmas) is proposed as a hypostratotype, in which the deposits of the lower subformation of the Uk suite are most fully represented in comparison with the stratotype along the river Yuryuzan (Ust-Katav). Cavernous-fractured limestones of the Uk Formation with layers enriched by a bitumen (?), may be regarded as an interesting search object for hydrocarbons, taking into account that a large hydrocarbon deposit has been discovered in the silicified cavernous-fractured dolomites of Kamovskaya Formation of the Upper Riphean of the Siberian platform.

A humite group mineral, Ti-bearing hydroxylclinohumite, referred to natural compact water-containing magnesian silicates (DHMS phases) was found for the first time in podiform chromitites. The finding was made in chrome ores of the Paity Plateau located in the northern part of the Voikar–Synya ultramafic massif of the Polar Urals. Chromitites deposited in the dunite body located at the contact of apoharzburgite amphibole–olivine–antigorite and amphibole–enstatite–olivine metamorphic rocks containing nonserpentinized harzburgite relics. According to the optical data and chemical composition, this mineral belongs to Ti-bearing hydroxylclinohumite, because it contains TiO2 (up to 5.64 wt

The results of study of the REE ID‒ICP‒MS, 86Sr/87Sr, and 147Sm‒143Nd AL ID-TIMS isotope systematics of spinel lherzolite from the Northern Kraka Massif, which is part of the largest (>900 km2) lherzolitic allochthon thrust over the bathyal and shelf deposits of the passive continental margin of the East European Platform, are reported. As a result, an isochron dependence (MSWD = 0.85) was revealed for the first time, which determines the age of 545 ± 26 Ma and the high value of the initial ratio (143Nd/144Nd)0 = 0.512390 ± 0.000054, corresponding to εNd = +8.9 within the model. The resulting REE, 87Sr/86Sr, and 147Sm–143Nd isotopic signatures indicate the melting of an already depleted protolith, which can be identified as a mantle source, with MORB-like parameters. The calculated isochron age of homogenization of the 147Sm–143Nd isotope system in combination with the available complex of geological and geochemical data allows us to place the Late Vendian phase (epoch) of folding and orogeny in the Urals in the interval of 545 ± 26 Ma. Comparison of these data with materials on the geology of Central and Western Europe allows us to correlate the Timanide structures formed as a result of this phase of folding with the Cadomian, which, based on global reconstructions of continents for the end of the Proterozoic, will ultimately authorize the hypothesis of the existence of the Cadomian orogeny on the periphery of Gondwana.

The authors summarize the available data on the structural-formational zonality of the Urals. Seven megazones of the Ural Fold Belt from west to east have been studied. The paleocontinental sector of the Urals, i.e., the former passive margin of the Baltica/Laurussia paleocontinent includes the Cis-Uralian Foredeep, the West Uralian and Central Uralian megazones. The paleo-island-arc sector, a collage of ophiolites, island-arc, and microcontinents (?), includes the Tagil–Magnitogorsk, East Uralian, and Transuralian megazones. These sectors are separate by the suture zone (the Main Ural Fault MUF). New data on the geochronology of the Bashkirian anticlinorium belonging to the Central Uralian Megazone are presented. Within the Central Uralian Megazone, the Paleozoic facies of the continental rise have been identified for the first time. The Tagil and Magnitogorsk island-arc terranes are correlated. The Tagil terrane began its development earlier and experienced two cycles of magmatism. The Magnitogorsk island arc is characterized by the shorter period of formation, gently dipping and less deep erosional downcut. The ideas, according to which the East Uralian megazone is considered a Madagascar-type microcontinent (Kazakhstan or Mugodzhary), are under discussion. The previously proposed Proterozoic age of the metamorphic rocks of the eastern segment of the Urals has remained unproven. The East Uralian Megazone, a rather young structure, is an integral part of the Ural Fold Belt and did not belong to hypothetical older megastructures. The main stage of folding, tectonic stacking, metamorphism, and granitization in the Ural Fold Belt are dated back to Late Paleozoic. It is shown that the observed latitudinal zonality of the Urals is determined by different present-day erosion depths. The vertical movements that determined the sublatitudinal zonality occurred mainly in the Middle–Late Triassic and were induced by north–south compression.

It is shown that the observed latitudinal zonality of the Ural Fold Belt is determined mainly by the different levels of erosion of different areas. Thus, the deep levels of the Magnitogorsk megasynclinorium were exposed in the southernmost part of the Urals, the West Mugodzhary zone, due to vertical uplift by about 5–8 km and the subsequent erosion of Paleozoic rocks of the Mugodzhary. The vertical movements, which created the sublatitudinal zonality of the Ural Fold Belt, occurred multidirectionally in the southern part of the region, in its western and eastern sectors. This could have led to the formation of faults with rotation along the Main Ural Fault. The differential uplifts in the different areas of the Urals occurred mainly in the Middle–Late Triassic and were probably caused by the north–south compression. This is confirmed by geological data and the results of analysis of the fission tracks in apatites and zircons. The sublatitudinal zonality of the Urals shows no direct link with the formation of any pre-Mesozoic minerals. Knowledge of the erosion depth in specific areas of the Urals is very important for assessing their metallogenic potential, in particular, for understanding the distribution of the youngest mineral deposits, in particular, oil and gas fields, and placers.

Comparative characteristics of gold minerals from gabbro of the Uralian Platinum Belt based on the author’s (Kumba massif, Serebryanskii Kamen massif, and Volkovskoe deposit) and literature (Volkovskoe deposit and Baronskoe ore occurrence) data are presented. The studied assemblages are dominated by native gold characterized by the following types: native gold without any impurities, copper gold, and copper–palladium gold. An unnamed phase with a composition similar to the Cu 2 PdAu stoichiometry has been found in gabbro of the Kumba massif for the first time in the Uralian Platinum Belt and Russia. The formation conditions of all types of gold minerals identified have been evaluated.

Research subject. Volcanogenic formations of the Navysh complex of the Ai Formation in the Taratash anticlinorium of the Southern Urals, which have been thought to be Lower Riphean. Results. The U-Pb dating of zircons from metabasalts of the Navysh complex were obtained, reflecting specific characteristics of their age. The isotope parameters of zircons of the К2247 sample divide them into two groups. The first group unites the ancient crystals aged Т1 = 2943 ± 31 and Т2 = 2713 ± 49 Ma, while crystals in the second group belongs to a much age - Т3 = 451.6 ± 9.1 and Т4 = 366.4 ± 6.0 Ma. No Riphean crystals were found in sample К2247. Conclusions. The dates obtained for the supposed Riphean complexes have shown that the Paleozoic magmatism took place not only in the eastern slope of the Urals, but also in the western slope. This process occurred several times.

The results of studying the aggregates of native iridium from chromitites of the Svetloborskii and Sosnovskii clinopyroxenite–dunite massifs of the platinum-bearing belt of the Urals and associated eluvial and ravine placers are presented. For the first time, their morphological features and the regularities of the internal structure are described. The association of the platinum group minerals with native iridium has been established. The structural and compositional features of native iridium aggregates and their space–time relationships with Fe–Pt intermetallic compounds have been studied. The data obtained made it possible to conclude that native iridium was formed in the temperature range from 850 to 1345°C at the magmatic stage of developing clinopyroxenite–dunite intrusions. In the course of our research, it was also established that the distribution of native iridium in ledge ores and placers might indicate either a deep erosional truncation of clinopyroxenite–dunite massifs or the particularity of the primary ore-forming matter.

Mantle plumes can be recognized by their magmatic expression as large igneous provinces (LIPs). However, identification of plumes in old, structurally complicated fold belts is particularly difficult due to deformation, which obscures the LIP record. On the other hand, fold belt regions are particularly important in the search for LIPs for at least three reasons: 1) they can represent prior plate margins associated with plume-generated continental breakup and LIP magmatism; 2) the deformation may expose basement rocks (containing LIP units) covered by younger sedimentary rocks elsewhere in the continental block; and 3) they preserve deformed remnants of oceanic LIPs and hot spot chains accreted during ocean closure. Herein we provide an initial survey of the plume /LIP record of one of the world's great orogenic belts, the Ural fold belt. The following events are identified: The 1750 Ma Navysh event is coeval with units in Sarmatia and Karelia (other parts of Baltica) and on other crustal blocks. The 1385 Ma Mashak event is associated with a range of ore deposit types, is part of Nuna supercontinent breakup, and is postulated to have had a global environmental impact linked to the Calymmian-Ectasian boundary. The ca. 720 Ma Igonino event can be approximately matched with 720 Ma LIPs in northern Laurentia, and elsewhere, which can be linked to the onset of the Sturtian glaciation (Tonian-Cryogenian boundary). The ca. 480 Ma Kidryasovo and 450 Ma Ushat events have age matches in Siberia and other crustal blocks; the ages approximately match the end-Cambrian and end-Ordovician periods, respectively. The 370 Ma Timaiz event belongs to the c. 370 Ma Kola-Dniepr LIP which is widespread in Baltica, has an age match in Siberia and collectively can be linked with the end Devonian period. An Early Carboniferous (350-320 Ma) event follows island-arc/continent collision and slab break-up in the Magnitogorsk zone. Three orogenic/postorogenic plume intraplate episodes are also described, the ca. 285 Ma Stepninsky monzogabbro-granosyenite-granite complex, the 308-304 Ma Kalymbaevsky lamproite complex and units that are coeval with the 251 Ma Siberian Traps LIP, linked to the Ural-Siberian superplume and with the end Permian mass extinction.

Research subject. Zircons from the Saf’yanovskoe Cu-Zn deposit rhyolite (Middle Urals). For the first time, zircon U-Pb dating for the rhyolite of the ore-bearing volcanic-sedimentary rocks of the Saf’yanovskoe deposit was performed. The volcanites are characterized by an andesite-rhyodacite composition and are localized at the southern edge of the Rezhevskaya structural-formation zone (SFZ) of the Eastern Ural megazone. A number of publications assign these rocks either to the basalt-rhyolite formation of the Middle Devonian, or to the basalt-andesite-dacite-rhyolite formation of the Lower-Middle Devonian.Aim. To estimate the age of the ore-bearing volcanic rocks under study using the U-Pb SHRIMP-II isotop ic system of zircon from the rhyolite of the eastern side of the Saf’yanovskoe deposit. By its chemical composition, the rhyolite belongs to the silicic varieties of subvolcanic rocks. Methods and results. The U-Pb isotopic system of zircon was studied by 5-collector mass-spectrometer of high precision and emission of the secondary ions SHRIMP-II (ASI, Australia) in the VSЕGEI Institute. U-Pb relations were investigated by a procedure developed by I.S. Williams. The U-Pb data obtained based on 13 zircon grains showed the age of 422.8 ± 3.7 Ma. Conclusions. The U-Pb dating of zircon obtained previously from the lens-shaped andesite bodies of the western side of the Safyanovskoe deposit gave the age of 422.8 Ma, which corresponds to the Przydoli series epoch of the Upper Silurian. We established that, among the volcanic rocks of the Saf’yanovskoe deposit, the effusive formations of the Upper Silurian are present.

The Ural mobile belt is an intracontinental epioceanic orogen that has already gone through all stages of the geodynamic development. Igneous rocks formed during each stage are important indicators for understanding the evolution of this belt and determining potential ore contents of its segments. We consolidated large datasets on petrogeochemistry and isotope geochronology of the Paleozoic (490–250 Ma) granitoids associated with the opening and evolution of the Ural paleoocean and the subsequent formation of the collisional orogen. Using these data, we have revised the ages of several tectono-magmatic events, clarified the paleogeodynamic settings for the generation of granitoids of different compositions, and described the roles of mantle-crust interactions and the plume factor in the formation of the mature continental crust in the study area. The results can be useful for geological mapping and improving the assessment of the potential ore contents in granitoid complexes that differ in origin and composition.

Mineralogical and geochemical studies of sulfide–platinum metal assemblages of the Khudolaz complex made it possible for the first time to substantiate their polygenetic nature. Three types of sulfide assemblages were distinguished. Their formation is associated with the segregation and fractionation of a sulfide melt, subsequent replacement of primary sulfides at the early hydrothermal stage, and partial redeposition of sulfides at the late hydrothermal stage. It was established (LA-ICP-MS data) that the removal of pla-tinum group elements (PGE) occurred due to primary sulfide alteration with their partial accumulation in newly formed sulfides. The structural position of PGM grains was studied using a scanning electron microscope. Platinum-group minerals (PGM) were crystallized during three stages: (1) from residual highly fractionated sulfide melts or immiscible metalloid melts captured by sulfides; (2) during the segregation of isomorphic impurities of PGE and chalcophile elements due to the exsolution of solid sulfide solutions; (3) during the interaction of antimony-enriched fluids with alternating sulfides.

Research subject. Magmatic complexes that are developed in the lower (volcanogenic-sedimentary) part of the Ai Formation of the Lower Riphean of the Taratash anticline in the Southern Urals. Results. For the frst time, the Lower Permian SHRIMP dating (288.6 ± 3.1 Ma by U-Pb method on zircon from monzogabbro) was obtained for a dike cutting the basalts of the Lower Paleozoic (420–450 Ma) age. Conclusions. On the eastern slope of the Urals there is a chain of massifs which are close in the age. The chain belongs to the Lower Permian Stepninsky monzogabbro-granosyenite-granite complex, represented by the Uiski, Vandyshevski, Biryukovski and Stepninski intrusions with the age of 281 ± 2, 280 ± 2 and 286 ± 2 Ma, correspondingly (U-Pb method after zircons, SHRIMP-II, VSEGEI) and earlier obtained dates 281 ± 4 Ma (Rb-Sr isochrone) and 283 ± 2 Ma (isotope Pb-Pb method after zircons). The Stepninsky complex was described earlier as plume-dependent. The monzogabbro dike, described in this paper, although being at a considerable distance from the Sepninsky complex, is situated at a strike of the chain of the stepninsky intrusions, is close to them by the composition and age and can be ascribed to the same plume episode. The idea of the plume character of the complex was ехрressed by us relatively long ago based on a superimposed character of the chain of the intrusions over the earlier, collisional Uralian structures. As for the geochemical character (monzogabbro) the dike conforms with one of two standard trends of the Stepninsky complex – monzonite (monzogabbro, monzodiorites, syenites).