Eclogites exposed along the northeastern boundary of the Belomorian orogen in the eastern Fennoscandian Shield formed as a result of Mesoarchean-Neoarchean subduction. Highly-deformed banded TTG gneisses with eclogitized mafic pods, lenses and dykes in the Gridino association of metamorphic rocks have been modified locally to have typical migmatite structures that formed as HP rocks decompressed through HP granulite-facies metamorphic conditions (16-12 kbar, 800-850 degrees C) to amphibolite-facies conditions (10-9 kbar, 600-700 degrees C). The migmatites are located with the boundaries between felsic and mafic lithologies, which are the most suitable place for partial melting, fluid migration, and component diffusion. Symplectic intergrowths of hydrous minerals (mica, epidote) together with quartz in the leucosome are important markers of arrested reaction textures that formed by reversed hydration crystallization of residual melts or by fluids where their infiltrated through migmatite areas. There are two potassic granitic leucosomes with contrasting geochemical signatures. Garnet and phengite-bearing leucosome replaces the host TTG gneiss and percolates mafic rocks. This leucosome is distinguished by a high Ba content, striking positive Eu and Sr anomalies and corresponding low concentrations of all other trace elements. The compositions of the leucosome record initial segregation and migration of melt away from the residual source and subsequent crystal fractionation, dominated by feldspars, of the escaped melt. Migration of anatectic melts led to the formation of small bodies of leucogranite that are characterized by high contents of trace elements and negative Eu and Sr anomalies. Leucogranites formed from portions of fractionated melt that percolated the migmatites and solidified. Anatexis occurred during the Neoarchean time (similar to 2.7 Ga). U-rich zircon domains were partly or completely affected by radiation damage that yield discordant scattered dates between 2.7 and 1.9 Ga, which are interpreted as reflecting a thermal and fluid overprint during evolution of Belomorian province that produced recrystallization and Pb loss in Neoarchean zircons.

The oval-shaped basin of Hudson Bay occurs near the center of the round-oval Archaean crustal domain of the North American continent. This paper presents models of the geological structure and evolution of the subcontinental lithospheric mantle underlying Hudson Bay and surrounding tectonic provinces based on geological interpretations of regional geological and geophysical data and results of seismic tomography investigations that have been conducted under the Hudson Bay Lithospheric Experiment. The experiment was aimed at lithospheric processes directly related to the origin of the North American craton and the Hudson Bay basin. Hudson Bay is located directly above the lithospheric keel of North America. The geological history demonstrates systematic "renovation" of the basin: (1) origin and evolution of the Neoarchaean Lake Minto basin (similar to 2.75 Ga); (2) accumulation of the Palaeoproterozoic volcanic-sedimentary filling of the epicontinental basin, relics of which is preserved on its passive margins (2.03-1.87 Ga); (3) origin of Ordovician-Late Devonian sedimentary sequence whose maximum thickness reaches 2.5 km; and (4) the development of Late Jurassic-Miocene sediment-filled ring-shaped trough immediately above the lithospheric keel. The Hudson Bay basin occurs above the lithospheric keel in compliance with thermomechanical model of ascending plume. Tomography studies have not detected evidence of either production or transformation of the lithosphere in the Palaeoproterozoic, which are implied by the model of the United Plates of America. Interpretations of tomography data reveal a vertical axial zone in the lithosphere beneath Hudson Bay, which extends from the lithosphere-asthenosphere boundary to the base of the crust or, perhaps, even to the present day surface. The zone is made up of relatively light low-velocity igneous rocks, probably a swarm of kimberlite dikes or pipes. At 2.75 Ga, the North American continent was a single continental mass with Hudson Bay at its center.

The Palaeoproterozoic Lauroscandia supercontinent received fundamental geological and geodynamic support based on the 3D characteristics of the deep structure of key tectonic units in the North American and East European megacratons. The deep structure of the western Reindeer zone of Trans-Hudson orogen (THO) most closely resembles the structure of sedimentary-volcanic belts along the eastern boundary of the Karelia craton formed during continental rifting. These belts were accompanied by vast depressions filled by the thick epicontinental volcano-sedimentary sequences, which were later affected together with the Archaean basement by high-temperature metamorphism. Some of the rifts could later be transformed into narrow short-lived oceans. The deep structure of the eastern Reindeer zone of THO is similar to Svecofennian accretionary orogen: structures of the crust and crust-mantle boundary point to a significant breakup of the continent, the origin of an ocean, and its later closure, involving a number of subduction zones, which operated almost simultaneously. The Sask craton should be viewed as a fragment of a Neoarchaean megacraton of North America. The main feature of the THO, Svecofennian Accretionary Orogen and Lauroscandia as a whole during Palaeoproterozoic evolution is the causal link with development of the Hudson Bay superplume that initialized a succession of huge events of platetectonic type. The head of the Hudson Bay superplume reached about 3000 km in the north-south direction and from 3000 to 4500 km in the east-west direction at different stages of evolution; 4500 km likely is a minimal estimate of the greatest dimension. The width of the Manikewan ocean reached more 1000 km, the width of the Svecofennian-Pre-Labradorian Ocean of similar to 2000 km that apparently also corresponds to a minimal value. The most significant temporal intervals in the Lauroscandia Palaeoproterozoic evolution (similar to 2.5 Ga and 2.2-1.8 Ga ago) coincide with events of global rank.

The Salma-type Archaean eclogites exposed along the northwestern boundary of the Belomorian Eclogite Province in the eastern Fennoscandian Shield formed as a result of the Mesoarchaean-Neoarchaean subduction and collision. The common protoliths of the Salma-type subduction-related eclogites were oceanic layered gabbro and volcanic-sedimentary assemblage. The eclogite-facies pillow lavas and associated alumina-siliceous sediments that fill interpillow space and intercalate with lava flows are the main objects of our work. The kyanite-garnet-phengite-quartz rocks formed after alumina-siliceous sediments contain fluid inclusions trapped in large relic quartz grains. The fluid inclusions yielded an isochore that corresponds to PT-conditions of a beginning of the Salma oceanic rock subduction from the seafloor level that generally confirms the sedimentary provenance of these rocks. The alumina-siliceous sediments underwent the eclogite-facies metamorphism at pressure no lower than 21 kbar and temperatures of 650-750 degrees C and transformed into kyanite-garnet-phengite-quartz rocks. During exhumation under granulite-facies conditions at temperatures up to 900 degrees C and pressure down to 9 kbar, eclogite facies metasediments underwent partial melting accompanied by disequilibrium breakdown of phengite + quartz association with formation complex polymineralic pseudomorphs consisting of feldspars, biotite, muscovite, kyanite, corundum, and dumortierite. U-Pb dating of Th-rich igneous zircon from melted metasedimentary and mafic rocks using the LA-ICP-MS and TIMS methods yielded the time of granulite facies event accompanied by partial melting processes at similar to 2.45 Ga. After this, zircon underwent fluid-induced alteration, causing partial dissolution followed by precipitation of new Th-poor zircon and zircon rims around ancient grains at similar to 1.9 Ga ago

The paper considers the results of calculation of the three-dimensional density model of the Earth’s crust for the territory of the Republic of Niger in conditions of incomplete initial geological and geophysical information. A brief description of the geological structure of the research region is given and the task of the study is formulated. The initial data set of density modeling is described, including: the anomalous gravity field, the initial model of the medium, the constraints on the desired solution, and the weight functions of redistribution of field incompatibilities. Inversion of the anomalous gravity field was performed in a three-dimensional formulation for a regular grid with a 25×25 km spacing in the plan and 14 layers of irregular vertical grid. The density model of the crystalline crust obtained by solving the inverse problem was combined with a priori data on the density of the upper mantle layer and the previously constructed layered model of the sedimentary cover of the region. The main features of the density model of the Earth’s crust are considered and its density heterogeneities are compared with the regional geological and tectonic data. The leading role of young structures of the West African rift System and their relationship with density inhomogeneities in the lower and middle crust of the territory of the Republic of Niger was noted.

The paper considers a range of tasks related to the processing and analysis of petrophysical data, which are effectively solved by the method of group accounting of arguments (MGUA). MGUA is a machine learning method that is an alternative to regression analysis and neural network modeling. The method was tested when working with information from the petrophysical database of crystalline and sedimentary rocks of the Voronezh Crystal Massif (VCM). The basis of the analysis technology is the formation of complex identification equations that allow you to generalize, analyze and effectively use petrophysical data. Previously, the use of such equations for estimating the ore content of nickel-bearing intrusions of the mamonsky complex was considered. Examples of solving problems of robust estimation and identification of petrophysical data are provided. It is shown that the identification models of the MGUA allow automating the procedure for detecting outliers in the data, assess the belonging of rocks to a certain material complex. Since petrophysical information is a necessary link in the geological interpretation of geophysical observations, the experience of obtaining complex models linking the density of metamorphic and intrusive rocks of the VCM with electrical resistivity and magnetic susceptibility is interesting.

A critical discussion of competing models of the geodynamic nature (oceanic or continental subduction) and age (Meso-Neoarchean or Late Paleoproterozoic) of the eclogite facies metamorphism in the Belomorian eclogite province (BEP) is based on the systematic analysis of the sum of previously known and newly obtained data characterizing the geological structure of the Salma eclogite association and features of zircons from eclogites, including the isotopegeochronological and geochemical characteristics, composition and distribution of mineral inclusions. Regular changes in the REE trends and crystallization-recrystallization temperature of porous zircons in eclogite-metagabbro illustrate the sequence of magmatic and metamorphic events in the Meso-Neoarchean and Paleoproterozoic. The susceptibility to recrystallization of zircons is due to partial metamictness and porous structure. The earliest (~2.9 Ga) zircon zones retain mag-matic-type REE trends. The microinclusions of the prenite-pumpelliite and greenschist facies minerals and the increase in the LREE and MREE concentrations indicate hydrothermal metamorphism in the spreading ridge and on the ocean floor at 2.9–2.82 Ga. Prenite, pumpelliite, albite, actinolite, chlorite, diaspore and saponite also form inclusions in the eclogitic garnet. An increase of LREE and MREE, the disappearance of the Ce positive anomaly, a change from negative to positive Eu anomaly at 2.82–2.78 Ga indicate that plagioclase was removed during the formation of the ‘garnet + omphacite’ eclogite association and the replacement of sphene with rutile. The eclogite facies metamorphism linked with subduction of the oceanic crust is also indicated by the microinclusions of garnet and rutile in zircon. The crystallization temperature in 700–900 °C range of the round-oval zircons from eclogites-metagabbronorites records the Neoarchean granulite facies metamorphism at 2.77–2.70 Ga, the negative Eu anomalies in the cores and rims of zircons indicate the participation of plagioclase in the metamorphic crystallization. Late (2.1–1.7 Ga) rims of porous zircons that occurred at 600–680 °C are distinguished by minimal REE concentrations, a change from a positive Eu anomaly to a negative one, and the appearance of a negative Ce anomaly, which indicates the presence of plagioclase, reducing type of fluids and, accordingly, low water activity that is characteristic of high-temperature metamorphism under stretching condition and mantle-plume activity. The deep Sm-Nd system reworking in the Belomorian tectonic province, including BEP, at ~1.9 Ga was caused by the crustal heating that spread from the Lapland granulite belt border in the west-south-westward direction. The Lu-Hf system in zircon reworking with a significant increase in radiogenic Hf indicates the recrystallization of a long-existing garnet, in which a significant amount of radiogenic 176Hf accumulated by 1.9 Ga as a result of the 176Lu decay. This contradicts the earlier suggestion of the eclogite garnet primary crystallization in the late Paleoproterozoic (1.94–1.89 Ga).

Competing evolutionary models and age of eclogite facies metamorphism, Mesoarchaean, Neoarchaean or Palaeoproterozoic, of the subducted Mesoarchaean oceanic crust (Salma association, Belomorian Eclogite Province) are discussed on a basis of systematic analysis of previously known and newly obtained data. Four main types of zircons were distinguished in eclogites: porous crystals with numerous inclusions from eclogite-metagabbro; wide-rimmed zircons with relict porous cores similar to previous type separated from garnetites; round-oval zircons from eclogite-metagabbronorite that are characteristic for granulite facies rocks and zircons with euhedral oscillatory zoning cores and oval grains that are characteristic for the eclogite facies pillow basalts. Regular changes in REE patterns and in crystallization-recrystallization temperatures of certain domains of the porous zircons display sequence of magmatic and metamorphic events. The similar to 2.9 Ga domains retain magmatic-type REE patterns. Low- and medium-temperature inclusions of prenite, pumpelliite, albite, actinolite, chlorite, diaspore and saponite in garnet and abundant microinclusions of the prenite-pumpelliite and greenschist facies in zircons with LREE-MREE enrichment indicate hydrothermal metamorphism in the spreading ridge and ocean floor at 2.9-2.82 Ga. Disappearance of Ce positive anomaly from REE pattern in zircon, change negative to positive Eu anomaly and LREE-MREE enrichment caused by plagioclase removal and replacement of rutile with sphene evidence eclogite facies metamorphism linked with subduction at 2.82-2.78 Ga. Temperatures in the 700-900 degrees C range of the round-oval zircons from eclogite-metagabbronorite records the Neoarchaean granulite facies overprint at 2.77-2.70 Ga. Series of the high temperature Palaeoprpoterozoic events was terminated by 2.1-1.7 Ga event marked by the rims with lowest REE that frame all types of zircons. Change from positive to negative Eu anomaly, retrieval of negative Ce anomaly indicate the presence of plagioclase, reduction type of fluids and low water activity characteristic of high-temperature metamorphism under stretching condition and mantle-plume activity. The deep reworking of the Sm-Nd isotope system in the Belomorian tectonic province at similar to 1.9 Ga, including the Salma eclogite association, was caused by the enormous crustal heating that spread from the Lapland granulite belt southward. Radiogenic Hf-176 enrichment of 1.9 Ga zircon indicates recrystallization of a long-existed garnet with release of significant amount of Hf-176.

The problems of using petrophysical data for studying deep structure of areas covered by sedimentary rocks are discussed. The correlation analysis of the density and gravity anomalies values revealed a complex character of the reflection of crystalline rocks of different density in anomaly of gravity field.

A model of Mesoarchaean spreading ridge subduction and related metamorphism, magmatism and deformation in an active continental margin is presented here. The eclogites exposed along northeastern boundary of the Belomorian orogen in the eastern Fennoscandian Shield were formed as a result of Mesoarchaean-Neoarchaean subduction and collision. The Belomorian eclogite province contains two eclogite associations have been recognized within TTG gneisses: (1) the subduction-type Salina association and (2) the Gridino mafic dykes. Protoliths of the Salma eclogites represent a sequence comprising oceanic layered gabbro, formed at similar to 2.9 Ga in a slow-spreading ridge. The subduction began in a time span 2.9-2.87 Ga, and eclogite-facies events occurred between ca.2.87 and ca.2.78 Ga. Injection of a mafic magma into an active continental margin, recorded by the Gridino dyke swarm, is attributed to subduction of a mid-ocean ridge, commencing at 2.87 Ga. The dykes represent typical fissure intrusions and underwent metamorphism to eclogite, granulite and amphibolite facies. The dykes divide into two compositions (Fe-Ti gabbro and Mg-Cr gabbronorite) which represent alternating episodes of arc and slab window magmatism. The Fe-Ti gabbros have high Ti and low abundances of fluid-mobile and other LIL elements compared to HFSE and plot in the MORE and within-plate oceanic basalt fields. The Fe-Ti gabbros formed from low-degree of partial melting from a depleted mantle source. This petrogenesis is consistent with slab window model in which magmas were derived by decompression melting of suboceanic mantle that upwelled into the opening beneath continental margin following spreading ridge subduction. The Mg-Cr gabbronorites have low Ti along with high abundances of fluid-mobile elements and other LILE compared to HFSE and plot in arc basalt fields that imply melting of subduction-modified hydrous subcontinental mantle. As the mid-ocean spreading ridge entered a trench, continental rocks above subduction zone underwent deformations with pseudotachylyte-bearing strike-slip faults development that is an evidence of a fossile earthquake. Paleoseismic event was limited to crustal conditions above the brittle-ductile transition, corresponding to temperatures below 450 degrees C and depths above 15 km. The slab window opening induced upwelling of anhydrous mantle and formation of the Fe-Ti gabbro dykes. The Mg-Cr gabbronorite was formed at slab window edges from metasomatized mantle. Summarizing evidences, such as ophiolites, eclogite, arc magmatism, we suggest that the modern style of subduction and plate tectonics began already in Mezoarchaean time 2.9-2.8 Ga ago. Special aspect of the paper is an argumentation of Meso-Neoarchaean age of eclogite facies metamorphism in the Belomorian eclogite province.

A 3D model of deep crustal structure of the Archaean Karelia Craton and late Palaeoproterozoic Svecofennian Accretionary Orogen including the boundary zone is presented. The model is based on the combination of data from geological mapping and reflection seismic studies, along profiles 1-EU, 4B, FIRE-1-2a-2 and FIRE-3-3a, and uses results of magnetotelluric soundings in southern Finland and northern Karelia. A seismogeological model of the crust and crust-mantle boundary is compared with a model of subhorizontal velocity-density layering of the crust. The TTG-type crust of the Palaeoarchaean and Mesoarchaean microcontinents within the Karelia Craton and the Belomorian Province are separated by gently dipping greenstone belts, at least some of which are palaeosutures. The structure of the crust was determined mainly by Palaeoproterozoic tectonism in the intracontinental settings modified by a strong collisional compression at the end of the Palaeoproterozoic. New insights into structure, origin and evolution of the Svecofennian Orogen are provided. The accretionary complex is characterized by inclined tectonic layering: the tectonic sheets, similar to 15 km thick, are composed of volcanic-sedimentary rocks, including electro-conductive graphite-bearing sedimentary rocks, and electro-resistive granitoids, which plunge monotonously and consecutively eastward. Upon reaching the level of the lower crust, the tectonic sheets of the accretionary complex lose their distinct outlines. In the seismic reflection pattern they are replaced by a uniform acoustically translucent medium, where separate sheets can only be traced fragmentarily. The crust-mantle boundary bears a diffuse character: the transition from crust to mantle is recorded by the disappearance of the vaguely drawn boundaries of the tectonic sheets and in the gradual transition of acoustically homogeneous and translucent lower crust into transparent mantle. Under the effect of endogenic heat flow, the accretionary complex underwent high-temperature metamorphism and partial melting. Blurring of the rock contacts, which in the initial state created contrasts of acoustic impedance, was caused by partial melting and mixing of melts. The 3D model is used as a starting point for the evolutionary model of the Svecofennian Accretionary Orogen and for determination of its place in the history of the Palaeoproterozoic Lauro-Russian intracontinental orogeny, which encompassed a predominant part of the territory of Lauroscandia, a palaeocontinent combining North American and East European cratons. The model includes three stages in the evolution of the Lauro-Russian Orogen (similar to 2.5, 2.2-2.1 and 1.95-1.87 Ga). The main feature of the Palaeoproterozoic evolution of the accretionary Svecofennian Orogen and Lauroscandia as a whole lay in the causal link with evolution of a superplume, which initiated plate-tectonic events. The Svecofennian-Pre-Labradorian palaeo-ocean originated in the superplume axial zone; the accretionary orogens were formed along both continental margins due to closure of the palaeo-ocean.

The model of supercontinent cycles is revisited on the basis of reevaluation of existing ideas on the geodynamics and tectonics of granulite gneiss belts and areals. Granulite-gneiss belts and areals of a regional scale correspond to mantle–plume (superplume) activity and form the major components of intracontinental orogens. The evolution of geodynamic settings of the Earth’s crust origin can be imagined as a “spiral sequence”: (1) interaction of mantle plumes and “embryonic” microplate tectonics during the Paleo- Mesoarchean (~3.80–2.75 Ga); (2) plume-tectonics and local plume-driven plate-tectonics within supercontinent during Neoarchean and Proterozoic (~2.75–0.85 Ga); (3) plate tectonics in the Phanerozoic along with a reduced role of mantle plumes starting from ~0.85 Ga.

In the Salma eclogite of the Belomorian eclogite province, a dumortierite–phengite–corundum–bearing quartz–feldspar rock has been studied: its primary HP mineral paragenesis included garnet, phengite, and quartz. The phengite–quartz rocks were formed during dehydration and/or melting of boroncontaining rocks when they were dipped in the Meso- Neoarchaean subduction zone to a depth of not less than 70 km. As a result of the subsequent superimposed high-temperature metamorphic events under PT conditions of high-pressure granulite facies, the phengite in quartz underwent incongruent dehydration melting with formation of complex polymineral pseudomorphs, consisting of feldspars, biotite, newly formed muscovite, kyanite, corundum, and dumortierite. New estimates of the metamorphic temperature (850–900°C according to the melting reactions of phengite and the dumortierite field of stability; about 1000°C by the reintegrated composition of feldspar–mesoperthite) that affected the HP parageneses of Salma eclogitized rocks are at least 50–100°C (or even more) higher than them estimated earlier.

В эклогитах Салмы Беломорской эклогитовой провинции изучены дюмортьерит-, фенгит- и корундсодержащие кварц-полевошпатовые породы, высокобарный минеральный парагенезис, который был представлен гранатом, фенгитом, кварцем. Породы формировались при дегидратации и/или плавлении боросодержащих пород при погружении их в зону мезо-неоархейской субдукции на глубину не менее 70 км. В результате последующих событий в РТ-условиях гранулитовой фации повышенных давлений фенгит в кварце подвергся инконгруэнтному дегидратационному плавлению с формированием сложных полиминеральных псевдоморфоз, состоящих из полевых шпатов, биотита, мусковита, кианита, корунда, дюмортьерита. Оценки температуры постэнклогитового события (850-900°С согласно реакциям плавления фенгита, и ~1000°С согласно реинтегрированному составу полевого шпата - мезопертита) на 50-100°С (и более) выше полученных ранее.

The structure of the Archaean crust of the North America has been studied based on the synthesis of geolo‐ gical and geophysical data, including seismic sections along LITHOPROBE Geotransects, magnetic and gravity anomaly maps, and seismic tomography data. The authors rely on the experience gained in the Russian Program of the deep geological and geophysical studies of the East European Craton. The juvenile Neoarchaean crust, containing the frag‐ ments of reworked Meso‐ and Paleoarchaean rocks, forms an asymmetric round‐oval‐shaped domain, wherein the geophysical, structural, and metamorphic parameters display a concentric zoning pattern. The Central zone occupies the Hudson Bay basin. The Internal zone (the northeastern and northern Superior Province) is mainly composed of the granulite facies of metaplutonic, metavolcanic and metasedimentary rocks. The External zone encompasses the southern Superior Province together with Hearne and Rae Provinces. This paper presents 3D crustal models of sou‐ thern Superior Province. The crust development resulted from rifting and a partial disruption of the continental crust, short‐term opening of the linear oceans, successive northward subduction and accretion of the ancient continental and juvenile Neoarchaean oceanic and island‐arc terranes between ~2.78 and ~2.70 Ga. Subsequent events in the epicontinental environment, including formation of the metasedimentary belts, granulite facies metamorphism and intense ore formation processes, took place within the range from ~2.71 to ~2.63 Ga. The SCLM morphology within the limits of the Archaean North American Craton can be represented as a flattened overturned cone with a vertical axis (down to a depth of ~350 km). The Hudson Bay basin is located right above the lithospheric keel. A number of the main features of the structure and evolution of the Archaean crust of the North American Craton, primarily the oval‐ concentric zoning, the important role of high‐temperature magmatic and metamorphic processes and mainly in‐ tracontinental magmatism and sedimentation, indicates the leading role of the mantle‐plume type processes. The Neoarchaean evolution of the North American craton represents the plate‐tectonic processes initiated by a super‐ plume. The Neoarchaean North American Craton is one of a series of similar phenomena that occurred ~2.75 Ga ago in a number of continental regions. The most important features, repeated to a certain degree in tectonic units of this type, are: (1) synchronous formation between 2.79 and 2.58 Ga; (2) mainly intracontinental development; (3) the prevalence of oval‐shaped synformal tectonic structures of different ranks with some form of concentric zoning; (4) high‐temperature magmatism (usually with the participation of enderbite‐charnockites and gabbro‐anorthosites) and metamorphism of the granulite facies; (5) a frequently repeated combination of high‐grade (granulite and high‐ temperature amphibolites facies) and low‐ or moderate‐grade (greenschist and epidote‐amphibolite facies) meta‐ morphic rocks; (6) the lower‐crust granulite‐basaltic layer that had formed and was deformed at the final stage of endogenic activity; (7) a thick lithosphere (the lithospheric keel reaches a depth of 250–350 km).

The objective of this paper is to represent the main features inherent to Grenville-Sveconorwegian Orogen (GSNO) and to propose a model of tectonic and geodynamic evolution of this orogen based on the results of research concerning similar Precambrian tectonic units in the East European Craton. The studies of the conditions and settings related to origin and evolution of GSNO are of special interest, because it is located geographicaly and in a certain sense ideologically in the center of Rodinia, a supposed Neoproterozoic supercontinent. GSNO originated in the MezoNeoproterozoic in the inner region of the Lauroscandia continent. At present, the synformal tectonic structure of GSNO is divided into two portions: Grenville sector along the southeastern margin of the Canadian Shield, and Sveconorwegian sector in the southwestern Scandinavia. The integrity of Lauroscandia was twice disturbed in the MezoNeoproterozoic when oceanic structures resembling the Atlantic Ocean were formed. Later on, the continuity of the continent was restored with the involvement of oceanic lithosphere subduction and accretion and obduction of the island-arc and oceanic terranes. We distinguish two stages in the GSNO history: (1) ‘preparatory’ stage (from ~1.90 to ~1.16 Ga), and (2) formation of GSNO proper (from ~1.19 to ~0.90 Ga). The manifestations of granulite-facies metamorphism were repeatedly recorded before the Grenville Orogeny at 1.67–1.66, 1.47–1.45, 1.37–1.35, and 1.20–1.18 Ga. The Ottawan stage of the Grenville metamorphism proper is dated between 1.16 and 1.05–1.03 Ga. Metamorphism at the base of Allochthonous Belt corresponds to high-pressure granulite facies and, in a number of places, to hightemperature eclogite facies (800–900 °C at pressure in the range between 14 and 20 kbar). The age of metamorphism of rocks within Paraautochthonous Belt is 1.05–0.95 Ga; metamorphic grade increases from the greenschist facies near the Grenville front to the high-pressure amphibolite facies near Allochthon Boundary Thrust showing an inverted metamorphic zoning. High-pressure granulite-facies metamorphism is characteristic of Sveconorwegian sector; and high-temperature eclogites are observed locally at the base of the allochthonous complexes and within the paraautochthonous complexes. A distinctive feature of GNSO is the abundant occurrence of specific intrusive magmatism. Massifs of anorthosite-mangerite-charnockite-granite (AMCG) and anorthosite-rapakivi granite (ARG) complexes formed 1.8–1.5 Ga ago frame the orogen as a wide arc. In the internal region of GSNO, these complexes were formed successively at 1.16–1.13, 1.09–1.05, 0.99–0.96, and 0.93–0.92 Ga. Later on, after the intrusion, the massifs unevenly underwent granulite-facies metamorphism. The high-temperature magmatism and metamorphism, numerous repeated thermal pulses and enormous crustal body that underwent high-temperature transformation point to a mantle plume as the most adequate source of thermal energy. The model of intracontinental development of GSNO comes into conflict with popular ideas, which assume origination of this orogen as a result of the collision and welding of the formerly distant continents (Laurentia, Baltica and Amazonia), which, as suggested, completed the assembly of Rodinia supercontinent. A conclusion is drawn that the concept of tectonic position and geodynamic evolution of GSNO, which is not a counterpart of the Tibet-Himalayan Orogen, should be revised.

The eclogites exposed along northeastern boundary of the Belomorian orogen in the eastern Fennoscandian Shield were formed as a result of Mesoarchean–Neoarchean subduction and collision. As has been shown previously, the common protolith of the Salma‐type subduction‐related eclogite was oceanic layered gabbro. In this paper, we characterize eclogites formed from volcanic–sedimentary rocks of the upper oceanic crust, which comprised pillow lavas and associated aluminous sediments that filled the interpillow space intercalated with lava flows. As a result of eclogite facies metamorphism, the aluminous sediments have been transformed into coarse‐grained garnet–phengite–quartz rocks under pressure no lower than 21 kbar at a temperature of ~650 °C. Alternatively, we cannot rule out the possibility that the garnet–phengite–quartz veins represent solidified felsic melts that were produced by melting of boron‐bearing hydrothermally altered oceanic crust in the subduction zone. During transfer to the upper crust under high‐P granulite facies conditions, phengite underwent incongruent melting with formation of complex polymineralic pseudomorphs consisting of feldspar, biotite, muscovite and kyanite with corundum and dumortierite. The peak of high‐T metamorphism during exhumation of the eclogites is estimated at 850–900 °C, i.e. at least 50–100 °C higher than previous estimates.

Two eclogite associations have been recognized within Belomorian TTG gneisses:（1）the subduction-type Salma association and（2）Gridino eclogitized mafic dykes.Protoliths of the Salma eclogites represent a sequence