Based on the proposed numerical model of the stress-strain state of polymineral rocks, which describes the formation of blastomylonites in the Yenisei Regional Shear Zone (PRSZ) in the Yenisei Ridge, the possibility of local tectonic overpressure exceeding the lithostatic pressure in rocks subjected to shear deformations is shown. For tectonites of the southern (Angara-Kan block) and northern (Isakovka terrane and Garevka complex) segments of the PRSZ, estimates of the maximum overpressure were obtained from 2–3 to 4–5 kbar, which range from 25 to 50% of the lithostatic pressure. It is shown that excess pressures can be preserved in a local volume on a geological time scale sufficient for their fixation in metamorphic minerals. Model values of overlithostatic pressure in garnet-amphibole tectonites and geobarometric estimates of peak values during stress metamorphism allow us to offer new evidence of pressure inhomogeneity in natural mineral associations. Using the results of numerical modeling for the evolution of fault metabasite blastomylonites, it was established that the overpressure at the stage of syn-deformation metamorphism in the shear zone are possible at temperatures up to 600–650°C and not reaching 800°C; the presence of fluid or partial melt prevents the occurrence of overpressure. The amount of excess pressure due to shear stresses depends on the mineral composition and structure of the rock.

It is established for the first time that biotite plagiogneisses from the Garevka metamorphic complex of the North Yenisei Ridge have geochemical characteristics of C-type adakites with island-arc melt sources. The Hf isotopic composition of zircons indicates the participation of several sources in the formation of the granite melt, including the juvenile mantle and older crustal rock protoliths with model ages THf(DM)с = 1838–1916 and 1965–2357 Ma, respectively. Based on the results of U–Pb dating of zircons, new pulses of Neoproterozoic endogenous activity at the western margin of the Siberian Craton (913 ± 11 and 915 ± 36 Ma for adakite-like granites and 932 ± 26 Ma for leucogranites), correlating with the Grenville tectonic events, were determined. These Grenville episodes of regional crustal evolution are correlated with the synchronous successions and a similar style of tectonothermal events along the Arctic margin of the supercontinent Rodinia. This confirms the spatial proximity of Siberia and the North Atlantic cratons (Laurentia and Baltica), which is consistent with the proposed Neoproterozoic paleogeographic reconstructions of Rodinia.

The relevance of the research is due to fundamental and applied aspects. The polymorphic modifications of Al2SiO5, namely kyanite, andalusite, and sillimanite - minerals of sillimanite group (MSG), are among the most important indicators of metamorphism in pelitic lithologies. The "triple point" corresponding to the equilibrium coexistence of all polymorphs Al2SiO5 is one of the most important invariant point in metamorphic petrology, and mineral associations with the participation of "triple point" polymorphs are informative for calibration of geothermobarometers. On the other hand, the Al2SiO5 polymorphs (andalusite, kyanite, and sillimanite), which are dominant constituents in aluminous metamorphic rocks of the North Yenisei Ridge, are gaining increasing importance as industrial sources for aluminum oxide, silumin, and aluminum. The polymetamorphic history of a series of metamorphic complexes of Al-rich metapelites in the Yenisei Range, with rocks containing the Al silicate triple-point assemblage (all three Al2SiO5 polymorphs) is illustrated by geologica-structural, mineralogical-petrological, and isotope geochronological evidence. In the studied aureoles, the overprinting of earlier mineral assemblages with the later ones during various geodynamic events obviously follows from the reaction microtextures and chemical zoning in minerals, the.-T trajectories of these rocks, as well as radiometric dating. These indicator features show that the Al2SiO5 polymorphs sequentially grew as a result of a complex polymetamorphic history due to the changes in the tectonic settings. In the Teya metamorphic complex, areas of development of metapelites of andalusite-sillimanite regional metamorphism have been established, within which the promising Panimba andalusite and Teya sillimanite deposits are concentrated. Products of the superimposed kyanite-sillimanite type of metamorphism in the thrust zone form a number of bimineral (andalusitekyanite) (Mayakon, Chirimba, etc.) and polymineral (andalusite-kyanite-sillimanite) (Vorogovo, Lower Veduga, Nerazgadannoe occurrences, etc.) Analysis of the resource base of alumina-containing minerals in the region shows that a number of promising for high-alumina schists (HAS) objects have been discovered in the North Yenisei Ridge, the formation of which is genetically related to tectonic-metamorphic processes of the Grenville and Baikal orogeny. Their constituent MSG, as well as HAS containing staurolite and chloritoid, have sufficient resources for their use in industry together with the explored deposits of bauxite, alumina iron ores, and nepheline syenites.

Research subject. Fe- and Al-rich metapelites of the Teya, Garevka and Angara complexes of the North Yenisei Ridge (western margin of the Siberian craton) were studied. Research methods. Recently-obtained geochronologic (SHRIMP II U-Pb zircon dating) and geochemical data on the distribution of major and trace elements were used to reproduce the composition and age of the protolith, along with the paleofacies formation conditions. Results. The ferruginous-aluminous metapelites of the North Yenisei Ridge consitute redeposited and metamorphosed products of Precambrian weathering crusts predominantly of the kaolinite rather than lateritic type, as was previously thought. The chemical weathering of rocks in the Early Proterozoic on the Yenisei Ridge did not reach the deep stage of lateritization with the formation of zones of final decomposition of aluminosilicates; however, this process was limited to the formation of weathering products of predominantly kaolinite-illite-montmorillonite-quartz composition. Conclusions. The petro- and geochemical characteristics of the studied metapelites are mainly due to the features of sedimentation during the formation of the protolith, which could have been formed due to the erosion of the Lower Proterozoic microgneisses of the Siberian craton with ages in the range of 1962-2043 Ma with the involvement of granitoid and volcanic admixture of mafic rocks into the erosion area and subsequent accumulation in marginal continental shallow basins under the conditions of a humid climate and a calm tectonic regime. These results are consistent with the data of lithofacies analysis and geodynamic reconstructions of the Precambrian evolution of geological complexes in the North Yenisei Ridge.

For the first time, the North Yenisei orogen was isolated in the Precambrian folded frame in the west of the Siberian craton. On the basis of a set of methods, polycyclicity and evolution of tectonic-metamorphic and magmatic complexes, the stages of its formation have been established at the boundaries (billion years): (1) Grenville (1.18-0.85), (2) Early Baikal (0.85-0.80), (3) the stage of destruction of Grenvillids (in the west, 1.18-0.80), culminating in the accretion-collision stage (0.80-0.60), and (4) late Baikal orogeny (in the east, 0.80-0.60). The correlation of the geological development of the North Yenisei orogen with the tyranids of the Urals is assumed.

Metapelites and metabasites within the Yenisei regional shear zone of the Yenisei Ridge underwent strong deformations with substrate recrystallization and blastomylonite formation during the Ediacaran. The geostructural, petrological, and isotopic–geochronological characteristics of development of the Late Neoproterozoic blastomylonite complexes marking the junction zone of the paleocontinental and paleoceanic sectors of the Yenisei Ridge have been analyzed. Two zones of heterogeneous blastomylonite complexes have been recognized from west to east, in order of increasing distance from the paleoceanic structures: (I) high-baric complexes of the suture zone and (II) frontal (above-suture) medium-baric and medium- to low-temperature complexes. The established differences in the Р–Т parameters of metamorphism between strongly and weakly deformed rocks were interpreted using well-known geodynamic models based on different tectonic mechanisms. As a result of the analysis, we found that the polychronous dynamic metamorphism of gneisses of the Angara–Kan block in the south and formation of the bulk of blastomylonites in the northern segment of the shear zone in the Northern Yenisei Ridge occurred with a 1.5–3 kbar increase in pressure along with insignificant increase in temperature and low metamorphic gradient dT/dH < 10°C/km compared to the background values of earlier regional metamorphism. This was probably due to crustal thickening as a result of rapid thrusting/subduction, followed by rapid uplift. The maximum excess values of the thermodynamic parameters of metamorphism were established in apometabasite tectonites of the suture zone with relict glaucophane schist associations that underwent metamorphism with a simultaneous significant increase in pressure by 3–5 kbar and temperature by 180–240°C with a higher dT/dH gradient of 15–20°C/km. Such excess Р–Т values could be due to progressive metamorphism, complicated by local heating of rocks during viscous deformations and excess oriented tectonic pressure over lithostatic in ductile shear zones. The data agree well with the results of numerical experiments, and this confirms the role of tectonic stress as an additional thermodynamic factor of metamorphic alterations in crustal suture zones.

The paper presents isotope–geochronological data on zircons from a granite–aplite dike that cuts garnet–hypersthene gneisses of the Kuzeyev unit of the Neoarchean–Paleoproterozoic Kan Group in the southern extension of the Ishimba–Tatarka regional shear zone, Kan River. The morphology and internal structure of most of the zircon grains indicate that the zircons are metamorphic and xenogenic and were captured by the acidic magma from the host rocks when the magma intruded the granulites. Based on these data, the obtained Paleoproterozoic U–Pb age of 1784 ± 6 Ma can be interpreted as the age of granulite metamorphism. The interpretation of available geological and isotopic data confirms a postcollisional age of the aplite, which was emplaced nearly synchronously with the formation of anorogenic leucogranites of the late phase of the Tarak complex, during the final stage of the formation of the Nuna supercontinent.

In the Angara part of the Yenisei Ridge, a sequential section of the metapicrite–basalt sequence and the overlying carbonate rocks of the Gorevskaya suite has been established, which is considered as a single volcanogenic–sedimentary complex formed at the turn of the Late Mesoproterozoic and Early Neoproterozoic in the riftogenic continental marginally continental southwestern paleobasin. In the section of the lower part of the Nizhnerechinskaya strata, metamorphosed picrobasalts and picrites prevail, in the middle and upper ones, there are basalts and ore-bearing Pb–Zn mineralization (Stepanovskoe ore occurrence). Rifting in the Earth’s crust in the Angara region, which occurred in the Late Mesoproterozoic–Early Neoproterozoic, led to the opening of the continental-marginal sea basin. The basalt–picrite volcanism and the accumulation of terrigenous–carbonate deposits, including ore-bearing deposits of the Gorevskaya suite, with the Gorevskoe Pb–Zn deposit, took place subsynchronously. Therefore, the paleobasin is interpreted as a relict of riftogenic nature on the western margin of the Siberian Craton, and the volcanic–sedimentary Nizhnerechinskaya stratum is interpreted as the lower potential stratum level of polymetallic mineralization in the Gorevskoe orefield.

In the Angara part of the Yenisei Ridge, a sequential section of the metapicritic–basalt sequence and overlying carbonate rocks of the Gorevskaya Formation is established. This section is considered as a single volcanic–sedimentary complex formed at the Late Mesoproterozoic–Early Neoproterozoic boundary in the riftogenic marginal–continental paleobasin in the southwestern Siberian Craton. It is proposed to introduce the metapicrite–basaltic sequence into the stratigraphic legend of the Shirokaya Group of the western Yenisei Ridge under the name “Nizhnerechinskaya Sequence”. In the studied section, metamorphosed picrobasalts and picrites predominate in the lower part of the Nizhnerechinskaya Sequence, while the middle and upper parts consist mainly of basalts containing Pb–Zn mineralization (Stepanovsky ore occurrence). At the contact with carbonate deposits of the Gorevskaya Formation, an alternation of volcanogenic rocks and terrigenous–carbonate sediments and metabasaltic sills are observed. The petrochemical and trace-element composition of metavolcanic rocks has much in common, which indicates the paragenetic relationship of rocks of this high-Mg rock association. All these rocks are enriched in Fe and Ti, while metabasalts and metagabbros show elevated alkalinity and P2O5 content. In terms of total alkalinity, metabasalt–picrobasalts deviate from the normal petrochemical series towards the subalkaline series, which correlates with their elevated Ti content. Basites enriched in alkalis, especially, in potassium and corresponding to trachybasalts are observed among them. The contents of incompatible trace elements clearly increase from picrites to basalts and reach maximum in trachybasalts, which show 1.5–3 times enrichment in high-field strength elements compared to the basalts. The paragenetic nature of the considered association is supported by the similar REE distribution patterns: (La/Yb)n = 6–7 at Eu/Eu* = 0.9–1. The Late Mesoproterozoic–Early Neoproterozoic rifting of the Earth’s crust in the Angara region led to the opening of the marginal–continental sea basin, where basalt-picrite volcanism occurred simultaneously with accumulation of terrigenous–carbonate sediments, including ore–bearing (Pb–Zn) rocks of the Gorevskaya Formation, which host the Gorevskoye Pb–Zn deposit. The basin under consideration is interpreted as a relict rift-related paleobasin on the western margin of the Siberian craton, while the volcanic–sedimentary Nizhnerechinskaya Sequence is considered as the lower potential stratigraphic level of the base-metal mineralization in the Gorevsky ore field.

Relevance. When mapping the vast areas of the Precambrian polymetamorphic complexes in the North Yenisei Ridge, there is a problem of metamorphism interpretation and phasing of geological development of a particular area along with thrust tectonics. The solution of these issues is also of great importance for the purposes of areas delineation of metamorphic rocks that are favorable for the detection of high-alumina (andalusite, kyanite, sillimanite) schists. Purpose of the work: to substantiate and itemize some geological prospecting, mineralogical and petrological indicator criteria for the development of high-alumina garnet-kyanite-staurolite blastomylonites of dislocation metamorphism formed by andalusite-bearing rocks of regional metamorphism. Research methodology: detailed mapping of structural-metamorphic zoning of dislocation (collisional) metamorphism in the Mayakon key area with sampling of polymetamorphic rocks for petrographic studies of mineral parageneses. Investigation of polished thin sections of polymetamorphic rocks by microprobe analysis with elucidation of minerals zoning, their chemical composition, calculation of the Р–Т paths of metamorphism and determination of the absolute age of blastomylonite formation based on the 40Ar/39Ar dating of biotite. Analysis and generalization of the results obtained for the Mayakon area and their comparison with other key areas of the North Yenisei Ridge. Results. At the Mayakon potential area, a progressive metamorphic zoning of kyanite-bearing blastomylonites has been identified, and the transitional I, outer II, middle III, and inner zones are determined as the dislocation metamorphism intensifies towards the Panimba thrust fault. Based on the compositions of garnets, biotite, and plagioclase, the P–T paths of the early regional metamorphism of andalusite-sillimanite type and late local kyanitesillimanite type were calculated. A list of geological prospecting, petrological and isotope-geochronological criteria for recognizing blastomylonites among rocks of regional metamorphism in thrust zones has been substantiated and itemized. Conclusions. Method of polymetamorphism reconstruction in the North Yenisei Ridge shows that tectonic inversion conditions took place in the Neoproterozoic, in the late Tonian era (~850 Ma ago In terms of occurrences, they are related to the final stage of the Grenville orogeny (1.1–0.85 Ga). The formation of blastomylonites of dislocation (collisional) metamorphism by metapelites of regional metamorphism in thrust zones is accompanied by an increase in the number of mineral phases and leads to a reduction in usable space of high-alumina andalusite schists.

The article proposes a model of collisional and accretionary events of the Neoproterozoic at the western margin of the Siberian Craton based on the results of geological, petrological, and geochronological studies of Precambrian complexes of the Yenisei Ridge and comprehensive geophysical data. Mineralogical and petrological evidence of paleosubduction is presented, represented by relicts of glaucophane-bearing high-pressure mineral assemblages in metabasites (630‒620 Ma) within the tectonic mélange of the suture zone and by metamorphosed ophiolites and island arc complexes of the Isakovka and Predivinsk terranes (700–600 Ma) of the Sayan–Yenisei accretionary belt. The proposed geodynamic evolutionary model of the Yenisei paleosubduction zone includes reconstructions for time intervals of 740‒700, 640‒600, 580‒540 Ma, during which a suture zone was formed as a result of collision of the Kas–Turukhansk microcontinent with the Siberian Craton. Tectonized fragments of the suture partially outcrop on the surface on the right bank of the Yenisei River. The bulk of the deformed and metamorphosed oceanic crust is buried beneath the Ediacaran and Phanerozoic sedimentary cover in the eastern part of the Kas–Turukhansk microcontinent, which is traceable by geophysical data. The history of the region’s geological development in the Late Meso‒Neoproterozoic correlates with synchronous endogenic events along the Arctic margin of the Nuna and Rodinia paleocontinents, which confirms the spatial proximity of the Siberian and North Atlantic cratons (Laurentia and Baltica) in a wide time range.

The Late Neoproterozoic U-Pb age for zircon of island-arc metadacites (691 8.8 million years) and basalts (572 6.5 million years) of the Kiselikhinskaya Formation of the Kutukasskaya Group was established for the first time. The manifestation of basaltic volcanism is associated with rift-related processes. The studies clarify the Late Precambrian stratigraphy of the Yenisei Ridge and the features of the evolution of the Sayan-Yenisei accretionary belt at the Neoproterozoic stage of its history. Folded-thrust structures of the junction zone of the Yenisei Ridge with the West Siberian Plate may be favorable in relation to the search for unconventional oil and gas traps.

The discovery of relics of glaucophane schist in high-pressure tectonites of the suture zone of Yenisei Ridge has provided evidence for a Cordillera-type convergent boundary controlled by subduction of the oceanic crust beneath the continental margin on the western side of the Siberian Craton. According to the microtextural patterns of rocks and the results of geothermobarometry, two stages of metamorphism were distinguished. The formation of high-pressure tectonites indicates the early stage in the evolution of the Paleoasian Ocean and the final stage in the Neoproterozoic history of the Yenisei Ridge including completion of the accretion–subduction processes on the western margin of the Siberian Craton.

Обнаружение реликтов глаукофановых сланцев в высокобарических тектонитах сутурной зоны Ениcейcкого кpяжа свидетельствует о проявлении на западе Сибирского кратона конвергентной границы “кордильерского” типа, контролируемой процессами субдукции океанической коры под континентальную окраину. По микроструктурным особенностям пород и результатам геотермобарометрии выделено два этапа метаморфизма. Формирование высокобарических тектонитов маркирует раннюю стадию развития Палеоазиатского океана и заключительный этап неопротерозойской истории Енисейского кряжа, связанный с завершением аккреционно-субдукционных процессов на западной окраине Сибирского кратона.

The occurrences of high-pressure tectonites localized in the tectonic suture zone of the Cis-Yenisei regional shear zone (CYRSZ) separated the cratonic and oceanic island-arc terranes were distinguished for the first time at the western margin of the Siberian Craton. Tectonites are characterized by high pressures (up to 15 kbar), which exceed significantly the background P–T parameters of regional metamorphism. The generation of tectonic overpressure is induced by rapid deformations along ductile shear zones, which is consistent with the numerical simulation results and thermodynamic calculations. These data confirm the important role of tectonic stress as an effective thermodynamic factor of metamorphic transformations in suture zones of the lithospheric crust.