The first data on P-T metamorphic conditions, coupled with U-Pb monazite and zircon ages, were obtained for Neoarchean aluminous gneisses in the central part of the Irkut terrane (the Sharyzhalgay uplift of the Siberian craton). Based on petrological observations, conventional geothermobarometry and thermodynamic modelling, the peak P-T conditions of metamorphism were found to be 760-780 degrees C and 6-6.8 kbar. This was followed by a 'clockwise' retrograde P-T path involving episodes of near-isothermal decompression and subsequent cooling, which is typical of collisional settings. Coupled U-Pb dating of zircon and monazite indicates that the metamorphism occurred approximately 2.55 billion years ago. Combining these new data with the Neoarchean age of the granitoids suggests a collisional event occurred in the eastern part of the Sharyzhalgay uplift around 2.55 Ga. The P-T parameters and P-T paths of Neoarchean metamorphism are similar to those of Paleoproterozoic collision-related metamorphism in the Irkut terrane. This implies that the tectonic settings were similar during these two periods.

Studies of the geological history of the Yenisei Ridge are important not only for understanding the tectonic evolution of mobile belts at the boundaries of ancient cratons but also for problem solving whether the Siberian craton was a part of the Rodinia supercontinent. The mineralogical-petrological, geochemical and isotope-geochronological studies yielded new data on the petrogeochemical composition, petrogenesis features, U-Pb age of zircon, and Sr and 147Sm-143Nd isotopic parameters for the rocks of the Ryazanovsky granitoid massif located near the Yenisei fault zone of the Yenisei Ridge. These rocks are represented by high-ferruginous peraluminous varieties and are comparable to A-granites or highly differentiated I-granites. Their composition evolves from normal to subalkaline granites and leucogranites, characterized by increased concentrations of highly charged and radioactive elements. Isotopic (Sr, Nd) characteristics of the rocks indicate generation from an ancient crustal substrate, the average age of which corresponds to the Paleoproterozoic. The formation of these granites at the Meso-Neoproterozoic boundary (1013±9.9 Ma) corresponds to the early stage of the Grenville orogeny and the formation time of the structure of the Rodinia supercontinent. This episode of regional crustal evolution is correlated with the synchronous successions and similar style of tectonothermal events on the periphery of large Precambrian cratons (Laurentia and Baltica), thus confirming the reliability of the proposed paleocontinental reconstructions of incorporation of the Siberian craton into the Rodinia.

Model calculations were used to estimate the compositions of melts during fractional crystallization corresponding to the formation of the Malyi Zadoi massif, which is located in the Irkut block of the Sharyzhalgai uplift in the southwest of the Siberian craton. It is shown that the gabbronorites of the massif are comagmatic to the plagioperidotites and olivine gabbronorites. The estimates obtained for the composition of the model melts are used to characterize the composition of the mantle source of the parental melt. The geochemical characteristics led us to suggest that the parental melt of the Malyi Zadoi massif was formed by melting an enriched source, a conclusion consistent with isotope data that indicate that the mantle Sm/Nd ratio decreased in the Archean. The probable source of the parental melt could consist of depleted lithospheric mantle material metasomatized by felsic melts coming from rocks of a subducting oceanic plate.

The paper presents geochemical and geochronological data on gneisses and granitoids from three deep boreholes (Yalykskaya-4, Danilovskaya-532, Srednenepskaya-1) in the basement of the southwestern part of the Nepa-Botuoba anteclise. Based on U-Pb dating of zircon, three stages of granitoid magmatism were identified:∼2.8, 2.0 and 1.87 Ga. At ca. 2.8 Ga magmatic TTG protolith of biotite-amphibole gneisses (Yalykskaya-4 borehole) were formed, which represent the Mesoarchean crust and experienced thermal effects at the terminal Neoarchean (∼2.53 Ga), typical of the Tungus superterrane of the the Siberian craton. Biotite gneiss-granites (∼2.0 Ga) (Danilovskaya-532 borehole) correlating in age with the granitoids of the basement of the Magan terrane and the Akitkan fold belt, were derived from a metasedimentary source formed by the erosion of mainly rocks of the Paleoproterozoic juvenile crust. The 1.88 Ga A-type granite (Srednenepskaya-1 borehole) correspond to the main stage of post-collision granite magmatism within the South Siberian magmatic belt. The ca.2.8 Ga biotite-amphibole gneisses mark position of the eastern boundary of the Archean crust in the south part of the Tungus superterrane with the area of the Paleoproterozoic juvenile crust, separated by a transitional zone, which intruded by granites having intermediate isotopic characteristics. The isotopic composition of Paleoproterozoic gneisses and granitoids indicates that marginal south part of the Magan terrane bordering with the Tungus superterrane – includes blocks of both Archean and Paleoproterozoic crust showing similarity with the Akitkan fold belt and accretionary orogens. The final amalgamation of the Tungus superterrane with blocks of the eastern part of the Siberian platform basement correspond to milestone of 1.88 billion years.

The paper presents geochemical and isotopic characteristics of Neoarchean (2.7–2.66 Ga) mafic granulites of the Sharyzhalgay uplift in the southwestern Siberian craton. Mafic and predominant felsic granulites compose fragments of the metamorphic complex among the Neoarchean and Paleoproterozoic granitoids. The mafic granulites are characterized by the mineral association Cpx + Pl ± Hbl ± Opx ± Qz and include two types with different major and immobile trace element contents. The dominant rocks of the first type have a wide range of Mg# and concentrations of TiO2 and immobile trace elements (REE, Zr, Nb), and mainly positive εNd(Т) values. The first type of mafic granulites show elevated (La/Sm)n and enrichment in Th and LREE relative to Nb, which is typical of subduction-related or crustally contaminated basalts. The absence of negative correlation between (La/Sm)n and εNd(Т) and a clear positive correlation of TiO2 with Nb testify against the effect of crustal contamination on the composition of the mafic granulites. The magmatic protoliths of the first type of mafic granulites are suggested to form by the melting of depleted peridotites of the subcontinental lithospheric mantle modified by melts derived from basalts or terrigenous sediments of the subducting plate. Mafic granulites of the second type have a narrower range of Mg#, TiO2 content, positive εNd(Т), flat rare earth patterns and no subduction signatures, which indicates an asthenospheric depleted mantle source. Mafic granulites contaminated by the Paleoarchean crust are characterized by increased (La/Sm)n, depletion in Nb relative to Th and LREE, and negative εNd(Т) values. Post-magmatic influence of granitoids leads to the enrichment of mafic granulites in biotite and apatite, an increase in concentrations of K2O, P2O5, a significant enrichment in Zr, Nb, Th, LREE, and negative εNd(Т) values. The difference between mafic granulites of the first and second types is not related to crustal contamination, but is caused by melting of two types of sources: asthenospheric and subcontinental lithospheric mantle. The subcontinental lithospheric mantle of the Irkut block was isotopically depleted at the Neoarchean time (∼2.7 Ga), and its enrichment in incompatible trace elements was likely caused by felsic melts generated from the rocks of subducting plate immediately prior to mafic magmatism.

— The paper provides evidence that collisional magmatism related to the Neoproterozoic (880−860 Ma) orogenic event occurred in the southwest of the Siberian Craton. Newly obtained data are presented on the major-component and trace-element composition, U−Pb (SHRIMP II) zircon age, and Sm−Nd isotope composition for rocks of the Gusyanka granitoid massif in the Yenisei fault zone of the Yenisei Ridge. The concordant U−Pb zircon age of the Gusyanka massif is 871 ± 11 Ma indicates that its rocks were formed in the mid-Early Neoproterozoic, simultaneously with the rocks of the Kalama and Eruda massifs in the Tatarka−Ishimba fault system, during the same stage of the collisional events at approximately 880–860 Ma. The calc-alkaline granites, granodiorites, and leucogranites of the Gusyanka massif are classified, on the basis of their high alumina content and trace element composition, as S-type and were derived from a metapelitic source. Many trace-element parameters of rocks of the Kalama and Eruda massifs correspond to those of low-potassium I-type granites, which were most likely derived from mafic rocks and tonalites. The granitoids of the Gusyanka massif, on the one hand, and the Kalama and Middle Tyrada massifs, on the other, differ contrastingly in Nd isotope composition. The source of the former was either metapelites of the Tungusik Group or metasedimentary rocks of the Sukhoi Pit Group, with the involvement of juvenile material. The melts of granites of the Kalama and Middle Tyrada massifs might have been derived from a source with the involvement of an older, possibly Paleoproterozoic, crustal material and a juvenile mafic source. Thus, the orogenic events at 880−860 Ma led to the generation of melts at different levels of the Paleo- to Mesoproterozoic crust of the trans-Angara region of the Yenisei Ridge. The geodynamic history of the region is correlated with the synchronous successions and similar style of tectono-thermal events along the peripheries of the large Precambrian cratons of Laurentia and Baltica, and this is consistent with paleocontinental reconstructions of the close spatiotemporal relations between these cratons, Siberia, and their incorporation into Rodinia.

—The paper presents data on the composition and age of mafic rocks of the shoshonitic series in the Irkut block of the Sharyzhalgai uplift (southwest of the Siberian Сraton). According to the U–Pb dating of magmatic zircon, the formation of monzodiorites of the Poludennyi massif and gabbro-dolerites in the endo- and exocontact zones of the Toisuk pluton occurred at 1.87 and 1.86–1.85 Ga, respectively. The intrusion of mafic magmas and their underplating into the basement of the crust under postcollisional extension resulted in the near-coeval mafic and granitoid magmatism in the Irkut block between 1.87 and 1.84 Ga. The Paleoproterozoic mafic associations belong to the shoshonitic series and are characterized by enrichment in incompatible elements, including Zr, and low negative εNd(T) values. These geochemical and isotopic characteristics point to the derivation of magma from a long-lived enriched-mantle source, such as the subcontinental lithospheric mantle. The crystallization of zircon from the last portions of the evolved mafic melt is evidenced by low zirconium saturation temperatures (710–965 °C) and zircon enrichment in U and Th with increasing Th/U, reflecting the growth of concentrations of highly incompatible elements in the residual melt.

—We present data on the geochronology, geochemistry, and Nd isotope composition of granitoids of the Gremyachikha and North Gremyachikha massifs (Kundusyul pluton) located in the Neoproterozoic metamorphosed island arc calc-alkalic volcanic rocks of the Talanovka–Bogorodka block in northern Kuznetsk Alatau (Martaiga uplift). The granitoids formed 890–880 Ma as a result of the accretion and collision of Neoproterozoic oceanic/island arc complexes with an unknown block formed by continent-marginal metasedimentary strata. The predominance of a metasedimentary source formed during the erosion of the early Precambrian and Neoproterozoic complexes is confirmed by the wide range of the ages of xenogenic zircons in the granitoids (2800 to 930 Ma) and by variations in the εNd values (−7.8 to −1.0) and model Nd age of the granites (2.20–1.64 Ga).

—Paleoproterozoic mafic associations of the Irkut block from the Sharyzhalgai uplift are gabbro-dolerite dikes and small gabbronorite and monzodiorite massifs, which formed at 1.87–1.84 Ga and were coeval with granitoids and basite intrusions of the South Siberian magmatic belt (SSB). All the Paleoproterozoic mafic associations of the Irkut block are characterized by the presence of biotite and alkali feldspar, enrichment in K2O, LILE, Th, and light REE, highly fractionated multielement spectra with sharp Nb and Ti depletion, and extremely low εNd(T) from –5.1 to –10.1. In these compositional features, they are similar to mafic complexes in the central and eastern parts of the SSB (the Baikal uplift and the western Aldan shield). Their geochemical and isotopic characteristics did not result from crustal contamination but point to derivation from the subcontinental lithospheric mantle (SCLM) enriched by reaction with felsic subduction-related and OIB-like mafic melts formed at a low degree of melting. The geochemically contrasting Paleoproterozoic gabbronorites in the Onot block of the Sharyzhalgai uplift are marked by depletion in K2O, Ba, LILE, Th, and light REE, weak depletion in Nb, and higher εNd(T) from –0.3 to –1.4. The gabbronorites indicate not only an increase in the contribution of a depleted source to their genesis but also the heterogeneity of the subcontinental lithospheric mantle below the south margin of the Siberian Craton. The formation of enriched SCLM domains throughout the South Siberian belt was mainly the result of Archean subduction-related metasomatic processes. The wide distribution of Paleoproterozoic mafic complexes with subduction geochemical signatures and negative εNd(T) on most early Precambrian cratons is due to global change in the composition and an increase in the heterogeneity of the subcontinental lithospheric mantle toward the end of the Archean.

An exotic block of andalusite-bearing garnet-cordierite-sillimanite gneisses was identified in the area of ultrahigh-temperature metamorphic complex of Angara-Kan block (southwestern Siberian Craton). Study of PTconditions of these rocks indicate that peak PT-parameters correspond to granulite facies at moderate pressure (T = 820 degrees C, P = 6 kbar) and was followed by clockwise retrograde PT-path with changing direction from near isothermal decompression to near isobaric cooling at pressure about 3 kbar. The new U-Pb SHRIMP and LA-ICPMS data on zircons and monazite indicate the time of granulite metamorphism at 1865 +/- 5 Ma. The age data, metamorphic mineral assemblages and micro-textures indicate that garnet-cordierite-sillimanite gneisses were not affected by later ultrahigh-temperature metamorphism (1.78-1.76 Ga) widespread in the Angara-Kan block. Thus, the block of garnet-cordierite-sillimanite gneisses can be considered as a fragment of the early granulite metamorphic complex, which was tectonically combined with UHT metamorphic block of the Angara-Kan terrane. The observations prove multistage metamorphic history of the Angara-Kan block and indicate collisional event at ca. 1.86 Ga typical for Siberian craton amalgamation. This metamorphic episode caused melting out of a large volume of post-collisional granitoids and probably played a key role in pre-conditioning of the crust for achieving of UHT conditions during the following metamorphism.

The (La/Nb) pm , (Th/La) pm , (La/Sm) pm , (NbY) pm ratios <1 in mafic rocks correspond to a depleted mantle source, while ≥1 corresponds to a undepleted/enriched source. (La/Nb) pm does not change during melting of mantle peridotites, so the Nd minimum is a characterictic feature of the lithospheric mantle metasomatized by fluid/melt. According to the isotopic Nd composition, there are two mantle sources: (1) depleted (+e Nd ), which corresponds to the asthenospheric and/or lithospheric mantle of restite origin, (2) enriched (-e Nd ) lithospheric, having decreased Sm/Nd due to metasomatism. Estimates of the character of the mantle sources of mafic rocks in terms of their trace element and isotopic composition can either correlate with each other or differ.

—The paper presents a synthesis of zircon U–Pb and Lu–Hf and whole-rock Sm–Nd isotope data from main early Precambrian (3.40 to 1.85 Ga) metamorphic and magmatic units of the Irkut block (Sharyzhalgai uplift, southwestern Siberian craton). The Archean complexes consist of relict Paleoarchean (3.4 Ga) melanocratic granulites and predominant Neoarchean mafic and felsic granulites (2.70–2.66 Ga), paragneisses (≤2.75 Ga), and gneissic granites (2.54 Ga). The Paleoproterozoic complexes include paragneisses (1.95–1.85 Ga), granitoids and charnockites (1.86–1.84 Ga), as well as mafic intrusions and dikes (1.86 Ga). Few detrital zircons with Hf model ages of ≥3.6 Ga mark the Eoarchean onset of crustal growth in the Irkut block. Isotopic data record two major stages of crustal growth in early Precambrian evolution of the Irkut block: Paleoarchean (3.6–3.4 Ga) and Neoarchean (~2.7–2.66 Ga). The Paleoarchean crustal growth was most likely associated with plume magmatism fed from depleted and primitive mantle sources. The spatial distribution of Paleoarchean crust is traceable in isotopic signatures of magmatic and detrital zircons from most of Mesoarchean to Paleoproterozoic units. The Neoarchean crustal growth from a depleted mantle source was due to subduction magmatism. Moderate crustal growth occurred in the Paleoproterozoic from 2.30 to 1.85 Ga. At the turn of 1.86–1.85 Ga, mafic magmas and products of their fractionation formed from both depleted and enriched sources under postcollisional extension; the latter sources were the subcontinental lithospheric mantle formed during Neoarchean subduction. Three major stages of crustal recycling have been established: Mesoarchean (~3.0 Ga), Neoarchean (~2.55 Ga), and Paleoproterozoic (1.86–1.85 Ga), which are characterized by near-coeval intracrustal melting and metamorphism. The recycling during the ~2.55 Ga and 1.86–1.85 Ga events apparently occurred in a collisional setting. The 2.7 Ga subduction-related felsic magmas also formed through the recycling of the Paleo-Mesoarchean crust. The hypothesized scenario for the geological evolution of the Irkut block is the dominant vertical growth and crustal recycling for about two billion years. Available isotope data record similar major crustal growth in the Paleoarchean and growth combined with recycling during the Neoarchean and Paleoproterozoic events in both the southwestern and northern and central parts of the Siberian craton. The Irkut block in the southwest differed in a long and continuous recycling during the Mesoarchean and pronounced Neoarchean crustal growth.

–We present data on the geochemical and Sr–Nd isotope compositions of rocks and on the Lu–Hf isotope composition of magmatic and xenogenic zircons from granitoids and gabbroids of the late Neoproterozoic island arc structure of the Lake Zone. Plagiogranitoids, gabbroids, and quartz diorites (559–542 Ma) formed at the late Neoproterozoic subduction stage of magmatism, and two-feldspathic granites (~483 Ma) mark Cambrian–Ordovician accretion–collision processes. We have established that the volcanic rocks of the late Neoproterozoic island arc and/or its oceanic base, which formed from the depleted mantle, were the mafic source of plagiogranitoids. This is proved by the overlapping positive εNd values of plagiogranitoids and the host volcanic rocks and by the commensurate εHf values of magmatic zircons from the plagiogranitoids and depleted mantle. The lower εNd values of gabbro and quartz diorites from the Tavan Hayrhan and Shuthuyn plutons, the lower εHf values of zircons from these rocks, and the high (87Sr/86Sr)0 ratios and K2O, Rb, and Th contents point to the generation of these rocks from a less depleted mantle source, namely, mantle wedge peridotites. The isotope composition of the latter changed at the previous subduction stage under the impact of fluids and with the contribution of subducted sediments. The least radiogenic Hf isotope composition of magmatic and xenogenic zircons from Ordovician accretion–collisional two-feldspathic granites of the Ih Zamiin pluton suggests their formation through the melting of the late Neoproterozoic–Cambrian island arc crust with the contribution of more differentiated crustal sources enriched in Th, Nb, and LREE and characterized by low εNd values. The age of xenogenic zircons (≤716 Ma) in the studied granitoids and gabbroids and their similarity in Hf isotope composition to magmatic zircons from the same rocks confirm the formation of the late Neoproterozoic island arc of the Lake Zone in an intraoceanic setting far from ancient continental sources similar to the Dzavhan microcontinent.

Based on trace element and Nd isotopic data on Early Precambrian mafic rocks, we traced the evolution of the mantle of the SW Siberian craton from the Archean to Paleoproterozoic. The sources of the Archean mafic rocks varied from weakly depleted to primitive mantle, i.e. the Archean mantle was less differentiated than modern one. From 2.8-2.7 Ga, it is assumed an existence of a metasomatically altered lithospheric mantle. The trace element and isotopic parameters of Paleoproterozoic mafic rocks reflect an increase in mantle heterogeneity and the formation of long-lived enriched sources. From the Archean to the Paleoproterozoic, the mantle differentiated in terms of trace element and Nd isotopic composition, due to separation and local metasomatism of the subcontinental lithospheric mantle.