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Using 3D numerical modeling, we analyze the formation of postcollisional granitoids of the Kara orogen in Northern Taimyr under conditions of elevated heat flow due to the orogen's breakup prior to its mantle plume episode (280–250 Ma). The initial geometry of the model area, the boundary conditions and physical properties for the crust and the mantle have been selected to reflect the structure of the crust in the junction zone of the Kara, Central Taimyr, and Siberian blocks. Comparing 2D and 3D modeling results with identical parameters and physical properties defined by the Rayleigh number shows that 3D modeling yields a more realistic and correct description of relevant magmatic processes. At the base of the modeled Earth crust an area of melting at a depth of ~46–50 km appears, possibly with slight input of mantle component, which induces magma uplift and the formation of closely spaced granitoid intrusions. Plutons with diameters 10–20 km were emplaced at depths 14–8 km during 15 million years, which is close to the actual geological position and timing of postcollisional stocks of the Kara orogen. [ABSTRACT FROM AUTHOR]

The paper presents new geological, geochronological, geochemical and Nd-Sr isotopic data on the Meso- Neoproterozoic dolerites of the Siberian Craton. New U-Pb baddeleyite and apatite ages of a E-W-trending dyke and two sills from southeastern Siberia are 982 ± 11, 977 ± 7, 970 ± 31 and 972 ± 60 Ma, respectively, extending the area of distribution of the event by more than 100 km to the north. The Sette-Daban intrusions are subalkalic mostly low-Ti dolerites, although high-Ti dolerites have been locally documented as well. Trace element abundances in dolerites vary from typical to E-MORB to OIB with arc-like signatures represented by high Th/Yb and low TiO2/Yb ratios. All dolerite samples display moderately positive εNd(t) values varying from +3.3 to +7.7 and indicating the magmas were derived from a depleted mantle source. E-MORB and OIB intrusions are attributed to the different degree of interaction of magma between the depleted asthenospheric mantle and regions within the sub-continental lithospheric mantle (SCLM) that were metasomatically enriched during earlier subduction events. Available data on Sette-Daban event distribution, composition and duration satisfy the characteristics of a typical Large Igneous Province (LIP). Similar age 1000–950 Ma mafic magmatism is also recognized in the Baltic and Amazonian cratons and can be potentially correlated with the Sette-Daban event. [ABSTRACT FROM AUTHOR]

Early Cambrian strata of the Siberian Craton accumulated within several relatively isolated basins of a tropical epeiric sea. The larger central part of the craton was occupied by the Turukhansk-Irkutsk-Olekma epicratonic carbonate platform. During Cambrian Stage 2 (Siberian Tommotian Stage, Osa horizon), the inner part of this platform was a mosaic of vast local uplifts characterized by a variety of shallow-water facies and separated by inner shelf depressions with condensed argillaceous carbonates. These shallow-water uplifts, such as the Nepa-Botuoba anteclise, yielded patch reefs having a distinct ring-shaped structure according to the common depth point 3-D seismic exploration method. Detailed studies of drill cores penetrating these buildups revealed an complicated facies complex within patch reefs and inter-reef depressions. The patch reefs themselves were differentiated into facies comprising a reef core, an inner reef lagoon, reef flanks and talus. These facies differed by assemblages and morphologies of reef-builders, relative abundance of mud and debris as well as by the composition and primary porosity patterns of early marine cements. Petrographic analyses show that different diagenetic pathways and porosity patterns relate to the primary composition of the patch reef. The significant diagenetic development of intercrystalline and intergranular porosity, vuggy and moldic caverns, intense dolomitization, and halite precipitation converts the reef flank and talus facies into high quality reservoirs. The most striking aspect of these early Cambrian reefs was the absence of metazoans and the dominance of microbial reef-builders although stromatolites were not formed and ooidal shoals were not accumulated. [ABSTRACT FROM AUTHOR]

The age of formation of the explosion pipes of the Chapinskii complex in the Chingasan magmatic belt in the northern part of the Yenisei Ridge is determined. U–Pb dating of zircon megacrysts from alkaline ultramafic rocks has established the values of 657.7 ± 13.4 and 647.6 ± 9.7 Ma for the Natalyinskaya pipe and Pipe no. 3, respectively. The intrusion of alkaline ultramafic explosion pipes of the Chapinskii complex corresponds to the time of manifestation of alkaline ultramafic magmatism along the southern and southwestern margin of the Siberian Craton. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diamondiferous kimberlites in the southern part of Siberian craton characterized by high TiO 2 and high mg# values in garnet xenocrysts. • Titanium in garnets is indicator of inhomogeneous composition of sub-continental lithospheric mantle. • High-Ti in garnets and high-Ti in kimberlites are result of asthenosphere activity SCLM under northern part of Siberian craton is generally poor in Ti. This contribution reports some 16,000 major and minor element analyses of garnet xenocrysts derived from 18 (out of the 21 known) kimberlite fields of the Yakutian Kimberlite Province (YaKP) on the Siberian craton in Russia. Using TiO 2 –in–garnet as an indicator of heterogeneity within the subcontinental lithospheric mantle (SCLM), as well as garnet mg# (mg#=Mg2+/(Mg2++Fe2+)*100), we distinguish three subpopulations of garnet: 1) high content of TiO 2 (0.26–0.50 wt%) and high mg# (80.6–82.6) garnet xenocrysts are common in the southern diamondiferous kimberlite fields; 2) garnet xenocrysts with low content of TiO 2 (0.06–0.26 wt%) and relatively high values of mg# (78.8–81.7), which prevail in the northern 'barren' kimberlite fields; and 3) three anomalous northern kimberlite fields (Chomurdakh, Ogoner-Yuryakh, Toluopka) characterized by the predominance of garnet xenocrysts with high TiO 2 content (0.53–0.78 wt%) at relatively low mg# (76.9–78.3). It is reasonable to assume that relatively thin cratonic mantle lithosphere beneath the three anomalous kimberlite fields underwent intense metasomatic overprinting by melts and fluids injected from the underlying asthenosphere, which changed the compositions of peridotitic garnets significantly. An interpretation of the data presented in this study is that the generally high TiO 2 contents of kimberlites in the northern YaKP (>1.5 wt% TiO 2) are a primary magmatic feature of asthenospheric origin because the lithospheric mantle traversed by these kimberlite magmas is TiO 2 depleted. We propose a model in which the relatively thin SCLM of the northern Siberian craton provided less opportunity for high-TiO 2 asthenospheric kimberlite melts to interact and change compositions on their way to the Earth's surface. The high-TiO 2 kimberlites of the northern YaKP may thus represent a good approximation of the primary compositions of natural kimberlite melts. [ABSTRACT FROM AUTHOR]

New data on the U–Th–Pb geochronology, mineralogy, geochemistry, and Sm–Nd and Rb–Sr isotopes for granitoids and the associated subalkaline rocks of the Tarbagannakh pluton of the Allakh-Yun tectonic zone in the Verkhoyansk fold-and-thrust belt are presented. These rocks, including trachyandesibasalt dikes, combined into the Uemlyakh complex, were formed about 120 Ma from a continental crust source probably with input from an enriched mantle component. Rapakivi granites are reported for the first time among them; their origin is reference for understanding the geodynamic conditions of formation of rocks in this complex. A tectonic model for the formation of these rocks due to slab break-off during the development of the active continental margin in the Aptian age is proposed. It is discussed that this magmatism was conducive for the widespread development of metasomatic processes until the end of the Aptian age and was at the same time a source of the coinciding spatially gold mineralization of the Okhotsk–Koryak metallogenic belt. [ABSTRACT FROM AUTHOR]

Xenoliths in kimberlites are the most promising material for studying the composition and structure of the lower levels of the continental crust. This study is aimed at the estimation of P–T parameters and fluid regime of metamorphism for garnet–biotite–feldspar and orthopyroxene–garnet–biotite–feldspar rocks found as xenoliths in kimberlites of the Yubileynaya and Sytykanskaya pipes, Yakutian kimberlite province. The seven studied samples show inverse dependences of relative contents of garnet and orthopyroxene, orthopyroxene and biotite, garnet and plagioclase, plagioclase and potassium feldspar. This indicates a consistent series of transformations of the assemblage garnet + plagioclase + orthopyroxene ± quartz to the assemblage garnet + biotite + potassium feldspar. In this process, the replacement of plagioclase by potassium feldspar was the leading reaction. Evidence of this reaction is specific reaction textures in the rocks, negative correlations between the contents of the minerals, and petrochemical characteristics of the rocks. Modeling of the mineral assemblages of the xenoliths using the pseudosection approach (PERPLE_X) revealed two groups of rocks corresponding to different depth levels of the Siberian cratonic crust. For rocks without orthopyroxene or with this mineral as single relics, the pressure was estimated at 9.5–10 kbar, and it is 6–7 kbar for orthopyroxene-bearing samples. The xenolith rocks have close metamorphic peak temperatures of 750–800°C. They experienced 200–250°C cooling and 3–4 kbar decompression, regardless of the level of the crust at which they had initially occurred. This indicates that the metamorphic evolution of the rocks during their exhumation was probably associated with collisional processes during the amalgamation of individual terrains of the Siberian craton. Xenoliths enriched in K-feldspar might have been products of metamorphic reactions with participation of aqueous–(carbonic)–salt fluids, which were sourced from basaltic magmas in the lower crust. The most strongly metasomatized rocks were located closest to the place of accumulation of crystallizing magmas. [ABSTRACT FROM AUTHOR]

We present a tectonothermal model showing the evolution of magmatism during the late Paleozoic postcollisional (pre-plume) development stage of the Kara orogen in northern Taimyr, Central Arctic. The model is based on new and published structural, petrologic, geochemical and geochronological data, as well as thermophysical parameters obtained for the Kara orogen that includes large amounts of syncollisional and postcollisional granites that formed due to the collision of the Kara microcontinent and the Siberian craton. Based on geological, geochemical and U–Th–Pb isotope data, the granites have been divided into syncollisional and postcollisional intrusions formed at 315–282 and 264–248 Ma respectively. Our previously published tectonothermal model [1] concerned the syncollisional formation stage of the Kara orogen at 315–282 Ma, during which the emplacement of anatectic granites took place. In this new study, we focus on the evolution of postcollisional magmatism in the orogen at the Permian–Triassic boundary. The existence of multiple bodies of allochthonous granitoids aged 265–248 Ma in the Kara orogen that predate the extensive eruption of the Siberian traps (~250 Ma) motivates us to reconstruct the thermal state and melting mechanisms of the crust on the "pre-plume" stage. To solve this problem, numerical modeling of the thermal, tectonic, and magmatic evolution of the Kara orogen's crust is used alongside geochemical and isotope data that reflects the magmatic sources of the granitoids. [ABSTRACT FROM AUTHOR]

Northwestern segment of the Precambrian Yenisei Ridge contains ophiolite and is known in literature as the Isakovka Terrane or Isakovka domain. We suggest to divide it into two belts: Kiselikha (western) and Torzhikha (eastern), which differed in geodynamic regime during the Late Neoproterozoic (750–600 Ma). It is believed that the Kiselikha belt is mostly composed of volcanic rocks erupted at island arc setting in the second half of the Neoproterozoic, and that collision of this arc with the Siberian Continent formed the Yenisei Ridge orogen. This idea has not been sufficiently supported by geological and geochronological data. Dating of four detrital zircons samples extracted from sedimentary and volcanic-sedimentary rocks in the southern part of the belt revealed that the sampled strata belong to three different Precambrian levels: the Mesoproterozoic, the mid-Neoproterozoic (800–750 Ma), and the end of the Neoproterozoic (620–600 Ma). Thus the authorized stratigraphic layout of the belt, as well as its proposed island-arc origin requires revision. By this paper we announce the identification of the Kiselikha Terrane , which was a part of active margin of the Siberian Paleocontinent at the beginning of the Neoproterozoic. Approximately in the middle of the Neoproterozoic, this block was rifted off Siberia and further evolved as a microcontinent bounded by an active margin from the outer side. [ABSTRACT FROM AUTHOR]

Petrographic, geochemical and U-Pb geochronological research studies are done into cataclastic granitoids of the southeastern part of the Irkutsk block of the Sharyzhalgay basement uplift of the Siberian craton – the uplift which is considered southern part of the Tungus superterrane according to most of tectonic schemes. The representative sample of these granitoids corresponds to granodiorite in its geochemical properties and is characterized by high contents of Al2O3, Th, Sr, Ba, low concentrations of K2O, Nb, Y, Yb, a highly fractionated rare earth elements pattern (Lan/Ybn=284), and the absence of europium anomaly. U-Pb geochronological studies of zircon from cataclastic granodiorite were carried out independently by two methods: SIMS and LA-ICP-MS, which showed good consistency of the results. The U-Pb age of the cores of zircon grains with magmatic zoning corresponds to 2893±19 Ma (SIMS method) and 2889±16 Ma (LA-ICP-MS method). These results can be interpreted as the age of the Archean granodiorite protolith. The rims of zircon crystals with the Archean cores, as well as the individual zircon crystals with parallel zoning, yielded ages of 1855±6 Ma (SIMS method) and 1864±5 Ma (LA-ICP-MS method), which record the time of granodiorite transformations. The age of about 1.86 Ga corresponds to the main Early Proterozoic stage of metamorphism, migmatization and magmatism, which show their widespread occurrence in the Sharyzhalgay basement uplift. This age estimate together with the previously published ages for metamorphic and their synchronous magmatic events in the Sharyzhalgay uplift allowed concluding that the Tungus superterrane joined the earlier formed core of the Siberian craton in the time interval 1.85–1.88 Ga. The final stage in the Siberian craton formation is the development of the South Siberian post-collisional magmatic belt, intersecting all large Early Precambrian blocks of the southern part of the Siberian craton, already united into a single structure.

In this study, we present the results of U–Pb (ID-TIMS) geochronological studies of calcic garnet from the alkaline ultramafic complexes of Eastern Sayan province (eastern Siberia). New U–Pb ID–TIMS garnet ages obtained from different rocks of Bolshaya Tagna (632 ± 2 Ma) and Srednaya Zima intrusions (624 ± 5 Ma), as well as previously published garnet ages of the Belaya Zima complex (646 ± 6 Ma), allow us to constrain the timing and duration of episodes of alkaline ultramafic magmatism in Eastern Sayan province (619–651 Ma). Variations in the chemical compositions of rocks from three massifs indicate that the parental melts were separated from different magmatic chambers generated during the same episode of mantle melting. This study further highlights garnet U–Pb dating as a potentially robust, high-resolution geochronometer to constrain the evolution of the main pulse of alkaline ultramafic magmatism in the large magmatic provinces. [ABSTRACT FROM AUTHOR]

Two new mineral species of the crichtonite group: botuobinskite, ideally SrFe2+(Ti4+12Cr3+6)Mg2[O36(OH)2] and mirnyite, ideally SrZr(Ti4+12Cr3+6)Mg2O38, occur as inclusions in mantle-derived Cr-pyrope xenocrysts from the Internatsionalnaya kimberlite pipe, Mirny field, Siberian craton. Botuobinskite forms needle- and blade-like acicular crystals up to 1 mm in length and up to 30 μm in diameter, a large platy inclusion (700 × 700 × 80 μm) and roughly isometric grains (up to 80 μm). Mirnyite occurs as needle-and blade-like elongated inclusions (up to 1 mm). Both minerals are jet-black, opaque and exhibit a metallic lustre. In plane-polarised reflected light, botuobinskite and mirnyite are greyish-white with a weak brownish tint. Between crossed polars, the new species show distinct anisotropy in shades of bluish grey to greenish-brown. Neither bireflectance nor pleochroism is observed. Calculated densities for botuobinskite and mirnyite are 4.3582(5) and 4.3867(3) gm/cm³, respectively. The crystal structures of botuobinskite and mirnyite have been refined (R = 0.0316 and 0.0285, respectively) from single crystal X-ray diffraction data. The minerals are trigonal, crystallise in the space group R3 ¯ (No. 148) and are isostructural with other members of the crichtonite group. The unit cell parameters are a = 10.3644(8) Å, c = 20.6588(11) Å and V = 1921.9(2) ų for botuobinskite and a = 10.3734(8) Å, c = 20.6910 (12) Å and V = 1928.2(2) ų for mirnyite, with Z = 3 for both. The Raman spectra of the minerals show strong peaks at 133, 313 and 711 cm–1. Infrared spectroscopy data for botuobinskite indicates H–O stretching of the hydroxyl groups. Botuobinskite and mirnyite have been approved by the IMA–CNMNC under the numbers 2018-143a and 2018-144a, respectively. Botuobinskite and mirnyite are named after the Botuobinskaya exploration expedition and Mirny town, respectively. The minerals may be considered as crystal-chemical analogues of other crichtonite-group species occurring in the lithospheric mantle (i.e. loveringite, lindsleyite and mathiasite). Both species commonly occur in intimate association with Cr-pyrope as well as other peridotitic minerals and exert an important control on the partitioning of incompatible elements during mantle metasomatism. [ABSTRACT FROM AUTHOR]

The article reports new data on previously undescribed lamellar-like (linearly oriented) structures in clinopyroxenes from mantle xenoliths of garnet pyroxenites (Obnazhennaya pipe, Northern Siberia). The origin and mineral diversity of lamellar structures in xenoliths from the Obnazhennaya pipe are supposed to be related to a breakdown of solid solutions during a decrease of P–T parameters. Our study shows that metasomatic recrystallization of initial clinopyroxene with linear exsolution structures leads to the formation of new secondary mineral assemblages. The secondary clinopyroxene reproduces (inherits) frameworks with linearly oriented inclusions, which are morphologically similar to the primary exsolution structures. Thus, the pyroxenite xenoliths from the Obnazhennaya pipe contain two generations of mineral associations with lamellar structures: primary and secondary. The primary association is composed of diopside, containing lamellae of enstatite, pyrope, spinel and rutile. The secondary (metasomatic) clinopyroxene contains half as much Al2O3 (3.4 wt %) and Na2O (1.7 wt %) and is enriched in MgO and CaO compared to the primary clinopyroxene. Nevertheless, the chemical composition of the secondary pyroxene still corresponds to diopside end-member. The metasomatic association comprises aligned pargasite (Al-rich amphibole) instead of orthopyroxene (enstatite) lamellae, and the secondary rutile is enriched in chromium (up to 3.1 wt % Cr2O3) in contrast to rutile from the primary mineral assemblage. [ABSTRACT FROM AUTHOR]

The paper presents detailed geological, petrographic, geochemical, and isotope data on the dolerites from dykes of the Baikal dike subswarm in the central part of the Baikal basement inlier of the Siberian craton. The main geochemical and isotope criteria were identified for classifying the dolerites that are similar in geological–structural position and mineral composition into three geochemical groups. Provisional age estimates of the dolerites are presented. The dolerites of the first and, perhaps, second groups compose Neoproterozoic (715 Ma) dikes. The first group includes medium- to coarse-grained dolerites, which form thick (more than 5–10 m) dikes. The dolerites of this group are characterized by low concentrations of Th (0.6–2.1 ppm) and Nb (3.3–9.2 ppm) and by ɛNd(T) = ‒0.5 to ‒3.9. Considered together, the geochemical and isotope data show that these dolerites could be produced as a result of the melting of a mantle source produced by mixing mantle components close in composition to oceanic plateau basalts and subduction-related subcontinental lithospheric mantle. The second group includes fine-grained dolerites from thin (1–5 m) dikes, including dikes located in contact with the dikes of the first group. The dolerites of the second group are characterized by higher concentrations of Th (3.0–5.3 ppm) and Nb (9.8–21.1 ppm) and by ɛNd(T) = –5.3 to ‒6.0. Geochemical and isotopic data on the dolerites of the second group indicate that continental crustal material was added to the mantle source unified for the dolerites of first and second groups. The third group includes medium-grained dolerites, which make up individual dikes that are contrastingly different in geochemical and isotope characteristics from the Neoproterozoic dolerites of the first and second groups. Dolerites of this group show low concentrations of Th (0.6–1.6 ppm) and Nb (2.7–5.1 ppm) at low values of (Th/La)pm (0.29–0.71) and 143Nd/144Nd (0.511223‒0.511544), which indicates that these dolerites may have been generated as a result of the melting of the subcontinental lithospheric mantle enriched in subduction components. Dolerites of the third group exhibit geochemical characteristics close to those of Paleoproterozoic (1.84 Ga) dikes of the South Siberian post-collisional magmatic belt. [ABSTRACT FROM AUTHOR]

Within the Anabar shield in the northern part of the Siberia, Late Precambrian mafic igneous units are widespread, which form dyke swarms of different ages of different trends. This paper presents new data on the composition, structure and U-Pb dating of the E-W trending Kengede dyke swarm. Three new U-Pb ID-TIMS baddeleyite ages (1496±7, 1494±3 and 1494±5 Ma) were obtained from three dykes, indicating that the Kengede swarm is part of the 1500 Ma Kuonamka large igneous province (LIP). The previously recognized Kuonamka Large Igneous Province (LIP) extends for 700 km from the Anabar shield to the Olenek uplift in the northern part of the Siberia and is potentially linked to coeval dykes and sills of the São Francisco craton and the Congo craton. The newly dated Kengede swarm is parallel to but offset by 50 km from the previously dated 1501±3 Ma Kuonamka swarm, and the identification of these two subparallel dyke subswarms of the Kuonamka LIP supports the earlier interpretation that mantle plume centre was located along the extrapolated trend of the dykes near the eastern or western margin of the Siberia. The paper examines features of sulfide Cu-Ni mineralization in dolerites of the Kengede and East Anabar dyke swarms and discusses potential Cu-Ni-sulfide mineralization linked to the Precambrian mafic dyke swarms of different ages in the north-east of the Siberia.

The problem of heat–mass transfer in the permeable areas above the asthenosphere zones was numerically studied based on an examination of the inclusion content in the minerals (olivine and clinopyroxenes) of igneous and metamorphic rocks of the lithospheric mantle and the Earth's crust; evaluations of thermodynamic conditions of the inclusion formation; and experimental modeling of the influence of hot reduced gases on rocks in the mantle beneath the Siberian craton. The flow of fluids of a certain composition from the upper-mantle magma chambers leads to the formation of zonal metasomatic columns in the ultrabasic mantle lithosphere in the permeable zones of deep faults (starting from the lithosphere base at 6–7 GPa). When petrogenic components enter from the magma pocket, depleted ultrabasic lithospheric mantle rocks change to substrates, which can be considered as the deep counterparts of crustal rodingites. Other fluid compositions result in strong calcination and pronounced salinization of the metasomatized substrates or an increase in the garnet content of the primary ultrabasic matrix. A region of alkaline rocks forms above these areas, which changes to pyroxenes, amphiboles, and biotites. The heat–mass transfer modeling for the two-velocity hydrodynamic model shows that gas–fluid and melt percolation lead to an increase in the thermal front velocity under convective heating and a pressure drop in flow. It is also shown that grospidites are considered to be eclogites, are found in the permeable zones of the lithospheric mantle columns serving as conduits for the melt/fluids and represent the products of the carbonated metasomatic columns. The carbonization caused by proto-kimberlite melts may essentially decrease the diamond grade of kimberlites due to carbon oxidation. [ABSTRACT FROM AUTHOR]

The northeastern Siberian craton stores numerous placers of diamonds that differ in morphology and texture, and originate from different types of primary deposits, primarily kimberlites. Analyses of mantle zircons selected from samples of alluvial and coarse clastic sediments in the watersheds of the Olenek and Kyutyungde rivers in the Anabar‐Olenek subprovince of the Yakutian diamond province provide constraints on kimberlite magmatism events in the area. The new U–Pb ages and typical kimberlitic signatures of the Kyutyungde zircons trace‐element patterns reveal three main magmatic events that produced kimberlites: Middle Paleozoic (Late Devonian to Early Carboniferous), Jurassic and Triassic. The Jurassic zircons (177–149 Ma) are mainly related to kimberlites in the proximal Kuoika‐Molodo and Khorbusuon fields. Triassic zircons (240–221 Ma) were probably released during large‐scale erosion of the eastern Anabar shield, however, the presence of such zircons in the Kyutyungde area indicates that kimberlites of the respective magmatic stage may exist within the immediate vicinity of the area. The only Middle Paleozoic zircon sample (358.6 Ma, D3‐C1 boundary) may originate from a proximal kimberlite within the Kyutyungde area. The presence of Middle Paleozoic kimberlitic zircons, along with harzburgite–dunitic pyropes, indicates that the primary deposit of diamonds and related minerals may exist near or within the Kyutyungde area. Late Ediacaran–Early Cambrian (573–473 Ma) mantle zircons found in Early Cambrian conglomerates of the area, along with other mantle minerals including Cr spinel of a diamond assemblage, record another Precambrian event of potentially diamondiferous magmatism in the Kyutyungde basin. [ABSTRACT FROM AUTHOR]

New data on the geology of the Kun-Manie Cu–Ni–(PGE) sulfide deposit in the Kun-Manie orefield, located on the eastern flank of the Stanovoy Orogen, adjacent to the Siberian Craton in the southeast, as well as a detailed description of the ores and major minerals and the distribution of PGE mineralization in the ores of the deposit are presented. The ore bodies are juxtaposed with the Late Paleoproterozoic (1.76–1.69 Ga) sills of the Kun-Manie gabbronorite–websterite–lherzolite complex. It has been established that the outlines of the disseminated Cu–Ni orebodies closely coincide with those of the ore-bearing sills of mafite–ultramafites. Brecciated and massive ores are confined to schists on the upper and lower sides of the orebodies. Pockety–disseminated and veinlet–disseminated mineralization is concentrated in the zones of ductile strain and along contacts between "beds" of rocks that differ in competence. It is demonstrated that the major ore minerals are pyrrhotite, pentlandite, and chalcopyrite; less common are pyrite, marcasite, cubanite, bornite, chalcocite, sulfoarsenides (gersdorffite and glaucodot), arsenides (nickeline), and nickel tellurides (melonite); magnetite and ilmenite occur in small amounts. It was established that PGE mineralization is represented by arsenides (sperrylite); sulfoarsenides (irarsite and hollingworthite); tellurides (Pd-melonite, merenskyite, and kotulskite); and tellurobismuthides (moncheite and michenerite). PGE, Ni, Ag, and Bi arsenides, sulfoarsenides, and tellurides, as well as native gold and silver, were established in the veinlet–disseminated, pockety– disseminated, and brecciated Cu–Ni ores. It is assumed that the concentration of a considerable part of the major sulfide minerals and the productivity of PGE mineralization are due not only to the complex processes of magmatic differentiation, but also to the sulfurization of magma differentiation products in zones of ductile (tectonic) deformations under the influence of fluids with recrystallization. One characteristic tendency is that the productivity of PGE mineralization increases markedly with S, As, Te, Bi, and Sb concentrations in fluids. [ABSTRACT FROM AUTHOR]

The paper presents data on granites and gneisses recovered by Kulindinskaya-1 hole drilled in the central part of the Siberian Craton. The biotite granites retain a porphyritic texture, correspond to I-type according to their compositional features, are enriched in LREE and moderately depleted in HREE, and have negative Eu, Sr, and Nb and positive Zr anomalies. The U−Pb zircon age of the granites is Neoarchean (2525 ± 10 Ma), with single cores of zircon grains dated at about 2.6 Ga, which likely suggests a crustal source of the granitic magmas. The model age TNd(DM) = 2.77 Ga of the granite shows that the crust from which the initial melts were derived had been formed shortly before the melting episode. In terms of age and all characteristics, the granites are close to those of the Yurubchen massif, which was drilled through in the western part of the Tunguska superterrane. The biotite gneiss was apparently derived from sedimentary rocks and was heavily reworked when the granites were emplaced. The enrichment of the gneiss in Cr and Ni is probably inherited from the sedimentary protolith, whereas the REE, HFSE, and LILE concentrations and distribution in the gneiss are similar to those of the granite. The concordant (D < 1%) U−Pb zircon ages (according to LA-ICP-MS data) broadly vary from 3284 to 2620 Ma, with two major peaks at 2717 and 2678 Ma. The model age of the gneiss TNd(DM) = 2.91 Ga confirms a contribution of the ancient crustal component to the sedimentary protolith of the rock. The minimum age of the detrital zircon, 2.62 Ga, determines the maximum age limit for sedimentation, and the minimum age limit is set by the age of the granite intrusions at 2.53 Ga. According to our data, the Archean gneisses and granites recovered by the Kulindinskaya-1 drillhole probably compose the eastern part of the Neoarchean Tunguska superterrane. Ereminskaya-101 drillhole, which was drilled 20 km northeast of Kulindinskaya-1, recovered gneisses with model ages TNd(DM) from 2.30 to 2.37 Ga, which belong to the adjacent Taimyr−Baikal suture zone with widespread Paleoproterozoic rocks. The contrasting crustal history of the adjacent complexes provides grounds to suggest that they were tectonically combined, which is an additional reason to consider the Taimyr−Baikal suture zone as a Paleoproterozoic collisional orogen. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Siberian Cratonic margins offers important clues for global paleogeographic reconstructions, particularly with regard to the complex geological history of Central Asia and Precambrian supercontinents Columbia/Nuna and Rodinia and its subsequent breakup with the opening of the Paleo-Asian Ocean. Here, we present an overview of geochemical, petrological, and geochronological data from a suite of various rocks to clarify the age, tectonic settings, and nature of their protolith, with an emphasis on understanding the tectonic history of the Yenisey Ridge fold-and-thrust belt at the western margin of the Siberian Craton. These pre-Grenville, Grenville, and post-Grenville episodes of regional crustal evolution are correlated with the synchronous successions and similar style of rocks along the Arctic margin of Nuna-Columbia and Rodinia and support the possible spatial proximity of Siberia and North Atlantic cratons (Laurentia and Baltica) over a long period ~1.4–0.55 Ga. [ABSTRACT FROM AUTHOR]

The Chadobets alkaline ultramafic carbonatite complex is located on the Siberian craton within the southern boundary of the Permian-Triassic plume activity. The dating of xenogenic zircons from the weathering crust of carbonatites of the Chuktukon complex yielded four clusters with ages of 1870–1820, 495–385, 290–210 and 215–162 Ma. The first two clusters correspond to the dates of activity of Paleoproterozoic granitoid magmatism and Paleozoic alkaline-mafic tectono-magmatic activity, widely occurred in the Siberian craton and its southern framing. The age of crystallization of alkaline rocks of the Chadobets complex falls within the interval of 255–240 Ma. Ar-Ar dating of damtjernite and carbonatite minerals of the Chuktukon complex falls within the intervals of 250.5±3.7 and 247.1±5.7 Ma, respectively. The crystallization ages of the mela-aillikites and damtjernites of the Terina complex, according to the Ar-Ar dating, correspond to the intervals of 257.4±3.9, 241.1±3.7, and 240±3.6 Ma. The age interval of 215–162 Ma based on zircons from the carbonatite weathering crust of the Chuktukon complex reflects the geochronology of superimposed processes and indicates the different stages of alteration of igneous rocks of the Chadobets complex. The data obtained on the age of crystallization of alkaline rocks of the Chadobets complex are consistent with the age interval of Siberian plume activity within a large igneous province (LIP).

The paper presents petrographic, geochemical, and new U-Pb zircon (LA-ICP-MS) geochronological data on the Upper Lena Fm. sediments which make part of the Cambrian sedimentary cover of the Siberian craton. The composition of lithic fragments in these clastic sediments, including mafic and felsic volcanics and granitoids, along with the correlation of major element ratios and the values of trace-element ratios point to predominant igneous (mainly felsic) rocks in the provenance. The U-Pb ages of detrital zircons from the sampled Upper Lena Fm. sandstones are mostly Early Paleozoic (∼500 Ma), with very few Archean-Paleoproterozoic determinations and quite many Neoproterozoic zircons. Ediacaran and Earliest Cambrian clastic sediments bearing Early Precambrian and Neoproterozoic detrital zircons, as well as Neoproterozoic and Early Paleozoic complexes of the Central Asian Orogenic Belt, could provide material for the Upper Lena clastic deposition. The geochronological evidence shows that the Upper Lena Fm. sandstones were deposited over vast territories of the southern Siberian craton in the Late Cambrian, in a single sedimentary basin, and originated from the same provenance. The Upper Lena deposition event in the Late Cambrian, immediately before the Ordovician period, makes a key milestone in the geological history of Siberia: the end of a large-scale Early Cambrian transgression and the beginning of gradual uplift of the southern craton margin, at least till the Carboniferous, which was associated with the formation of the Central Asian Orogenic Belt, a major tectonic unit of Asia.

We report results of paleomagnetic studies of mafic dikes and sills from the Tas-Yuryakh magmatic complex on the Olenek uplift in the northeast of the Siberian platform. The paleomagnetic record in the rocks corresponds to an episode of anomalous state of the geomagnetic field that persisted from the Ediacaran period (~580 Ma and younger) to the end of the Fortunian age. Paleointensity measurements indicate an extremely low value of the virtual dipole moment during this time. This presumably caused a disruption of the normal Geocentric Axial Dipole model, so much so that the world magnetic anomalies made a substantial contribution. We propose that the Antarctic anomaly influenced the magnetization of the Siberian craton rocks during this period of very low dipole moment. The high latitudes corresponding to the observed paleopole do not correspond to the actual paleogeography of Siberia and can be used for paleoreconstructions only after adjusting for this anomaly. The true position of the Olenek uplift at the Precambrian–Paleozoic boundary was close to 30° S above the southeastern periphery of the African (Tuzo) mantle hot field. [ABSTRACT FROM AUTHOR]

Novel data from mineralogical studies of the peridotite xenoliths from the Komsomol'skaya–Magnitnaya kimberlite pipe, Upper Muna field, Siberian craton, are presented. The mineral composition of 170 peridotite xenoliths (dunites, harzburgites, and lherzolites) is investigated. Based on these studies, it has been established that the lithospheric mantle beneath the Upper Muna kimberlite field is composed mainly of garnet and chromite-bearing dunites, harzburgites, and subordinate amounts of granular garnet lherzolites. The high proportion of peridotites with high-Mg olivines (Fo > 93 mol %) indicates the highly depleted nature of the lithospheric mantle peridotites. Based on the geochemical studies of the garnets, it has been found that the diamondiferous lithospheric keel underwent a low degree of metasomatic modification, mainly with the participation of carbonatite fluids/melts. Using the data on clinopyroxene monomineral geothermobarometry, it has been established that the thickness of the lithosphere in the area of the Upper Muna field at the time of kimberlite magmatism (~360 Ma) was about 220 km and the interval of the diamond window was about 95 km (from 125 to 220 km). [ABSTRACT FROM AUTHOR]

The mantle paleogeotherm under the Obnazhennaya kimberlite pipe (Kuoika field, Siberian craton) was reconstructed using the chemical composition of clinopyroxene xenocrystals and the FITPLOT program. The lithosphere thickness 187–193 km and surface heat flow 41–42 mW/m2 were measured for the Obnazhennaya pipe at the time of kimberlite magmatism in the Mesozoic. The lithosphere thickness was found to be much smaller than that in the central part of the Siberian craton (210–230 km), where Paleozoic diamond-bearing kimberlite pipes-deposits are located. It is however comparable to the highly diamond-bearing Kimberley field in the Kaapvaal craton (South Africa). The absence of diamonds in the pipes of the Kuoika field, but poor diamondiferous Dyanga pipe, might be associated with the more intense metasomatic alteration of the rocks within the lithospheric mantle of this region in the Mesozoic time, as compared to the central part of the Siberian craton in the Middle Paleozoic time.

The age of rocks of the Bolshetagninskii ijolite–syenite–carbonatite massif and ultramafic dykes within the Urik-Iya Graben in the southwestern part of the Siberian Craton was studied. An isochrone with an age of 640 ± 11 Ma was obtained by the 147Sm–143Nd method for rocks of the massif. 40Ar/39Ar dating of phlogopites from rocks of the dyke series provided two plateaus with ages of 644.1 ± 8.6 and 646.1 ± 8.6 Ma. The ranges of εNd(Т) values corrected for 640 Ma are from +4.2 to +5.0 for rocks of the massif and from +2.9 to +4.5 for dykes and characterize a mantle source close that of OIB. Ijolite and carbonatite of the massif have εNd(Т) values from +4.6 to +5.0 and εSr(Т) values from –7 to –10, which indicates a common silicate–carbonate parental melt for them. Variations in the initial (87Sr/86Sr)t ratio from 0.7025 to 0.7059 in dykes most likely reflect both the heterogeneity in the isotopic composition of the mantle source and the different degrees of contamination of mantle melts by the material of the upper continental crust. [ABSTRACT FROM AUTHOR]

Zircon xenocrysts from two diamond-barren kimberlite pipes (Leningrad and Ruslovaya) in the West Ukukit kimberlite field opened a 'window' to the buried crustal basement in the northern Siberian craton. Zircon U-Pb ages reveal a close affinity of the basement of the Khapchan belt to the Archaean Anabar province and a significant tectonomagmatic reworking in the Paleoproterozoic (~2.1–1.8 Ga) due to collision between the Anabar province and the Olenek province. The West Ukukit kimberlite field experienced multiple tectonomagmatic reactivation from ~670 to 144 Ma, which can be attributed to interaction of the deep crust with mantle-derived melts. Hf isotope composition of zircon xenocrysts reveals significant addition of juvenile material into the crust during the Paleoproterozoic orogeny in diamond-barren kimberlite fields, which is different from the reworking crust in the southern Yakutia diamondiferous kimberlite fields. Eruption of the Leningrad and Ruslovaya pipes were constrained as the Late Jurassic, much later than the well-known Late Silurian-Earth Devonian kimberlites in the West Ukukit kimberlite field. A NE-trending, >2000 km long kimberlite corridor is proposed to account for a prolonged lithospheric channel for episodic eruption of kimberlites in the Siberian craton. The diamond storage in the lithosphere beneath the West Ukukit kimberlite field may have been largely reduced by the Paleoproterozoic orogeny and Phanerozoic reworking. [ABSTRACT FROM AUTHOR]

We analyzed new geological and geochronological data on sedimentation and metamorphism in the junction area of the Aldan and Stanovoy Superterranes comprising the southern flank of the Siberian craton. The analysis was focused on early Proterozoic deposits belonging to the Udokan group. It is confirmed that highly metamorphosed rocks at the base of the Udokan group (Kolar subgroup of the Stanovoy suture zone) differ sharply from other rock associations included in this group (Chiney and Kemen subgroups of the Aldan Superterrane). They differ in the degree of metamorphic alterations, style of tectonic deformation, igneous complexes intruding them, and show a complete lack of copper mineralization. There are thus grounds to exclude the Kolar subgroup from the Udokan group. According to our data, the age of the sediments in the Udokan group, including the Chiney and Kemen subgroups, is 1.90‒1.87 Ga, i.e. in the study area, sedimentation lasted for no more than 30 Ma and proceeded simultaneously with the copper mineralization within the intracontinental extensional basin at the stage of collapse of the early Proterozoic orogen.

The Archean metamorphism in the southwestern Siberian craton was confirmed by the studies of the Kitoy and Irkutsk blocks. However, the parameters of the metamorphism process are still poorly investigated. The article presents the first results of studying the metamorphism conditions of garnet amphibolites sampled from the Kitoy sillimanite deposit. The reaction relationships of the studied minerals give grounds to distinguish two episodes of the regional metamorphism. At the end of the first episode, (Т=710–770 °С and Р=8.3–8.8 kb), the pressure reduced to 1.3–2.5 kbar at T=700 °C at the retrograde stage, and amphibole-plagioclase rims formed around garnet grains. During the second episode of metamorphism, the temperature reached 890 °С (granulite facies), and Cpx+Opx paragenesis replaced hornblende. The second episode of metamorphism is not evident in all the samples (considering the same bulk rocks composition of the rocks), which suggests its local character.

Deep, carbonate-rich melts are key constituents of kimberlites and are crucial for understanding the cycle of volatile elements in the mantle. On the Siberian craton, the Udachnaya-East kimberlite hosts extremely well-preserved nodules composed of chlorides + carbonates + sulfates, that do not present any relict sedimentary textures. These salty nodules display textures that are commonly observed in quenched liquids and may thus represent the very last stage liquid of the kimberlite. Alternatively, they could represent assimilated sedimentary material, or even post-magmatic hydrothermal alteration, because kimberlites are known to ascend through the lithosphere while assimilating material from their wall rocks. Here we focus specifically on those chloride-carbonate nodules, which are composed of 70% chloride + 30% alkali-carbonate and sulfate, and used two radiogenic systems (Rb-Sr, Sm-Nd) and the isotopic composition of sulfur, in addition to their major and trace element compositions (n = 3). We then compared the results with the same geochemical data on host kimberlites (n = 4), sedimentary cover (n = 3) and hydrothermal veins (n = 3). Taken together, our results show that the nodules are not the product of a contamination by the Cambrian sedimentary cover. Trace element patterns of the nodules display extreme enrichments in the same elements that are relatively depleted in the host kimberlite but also in kimberlites worldwide (K, Rb, Sr, Pb), suggesting that chloride-carbonate nodules are snapshots of the latest stage liquid present in the kimberlite system. Their isotopic compositions (Rb-Sr, Sm-Nd and δ34S) are consistent with a common magmatic source with their host kimberlite. We propose that chloride-carbonate nodules record a missing compositional endmember, which could explain the trend towards more radiogenic Sr isotope ratios at nearly constant Nd signatures observed in their host kimberlite, as well as in other kimberlites worldwide. This observed trend suggests the presence of a recycled component with high Rb/Sr (such as salts or terrigenous sediments) in the mantle sampled by some kimberlites, either in the lithosphere or the asthenosphere. This study highlights that the role of alkalies and halogens may have been underestimated in the genesis of kimberlites at depths where diamonds are stable, as well as in more evolved magmatic stages. Segregations of chlorides and carbonates occur specifically in sulfate-bearing kimberlites, which may thus sample a mantle domain in which sulfates with δ34S > 0‰ are dominant. The existence of such a reservoir could explain the apparent imbalance observed between the chondritic value (δ34S of 0‰) and the negative S isotopic compositions of mantle sulfides (MORB and peridotites). [ABSTRACT FROM AUTHOR]

The sulfur isotope anomalies ∆33S and ∆36S known today in ancient rocks exhibit common geochemical patterns reflected in the existence of a correlation like ∆36S ≈ –∆33S for sulfides from Archean formations of Australia, Africa, and America. To understand the scale of this phenomenon, we investigated the pattern of sulfur isotope fractionation in sulfides from rocks of the Irkut Block of the Sharyzhalgai Uplift of the basement of the Siberian Craton, as well as the Leksa ore occurrences located in the Karelian Province. It was shown that the objects of our study held ∆33S and ∆36S isotope anomalies. This leads to the conclusion that the geochemical processes responsible for the generation of sulfur isotope anomalies are much more widespread than was assumed until now and allows us to recognize them as a phenomenon of planetary significance. The fact that the relationship between ∆36S ≈ –1.0 ∆33S isotope anomalies demonstrates the same characteristics as in other Archean rocks of the most ancient shields worldwide indicates the similar conditions and mechanisms for fractionation of sulfur isotopes at the stages of its transformation in an atmospheric photochemical cycle. [ABSTRACT FROM AUTHOR]

Sedimentary successions and igneous rocks exposed in Eastern Sayan provide an important geological record on the tectonic evolution of the southwestern margin of the Siberian Craton during the Neoproterozoic. Here we present sedimentological and detrital zircon provenance data from key stratigraphic units, complemented by a new U-Pb zircon age of 718 ± 6 Ma from the mafic Nersa magmatic complex. Sedimentological and provenance data from the lower part of the stratigraphic succession (Karagasy Group) show that these rocks were deposited in a passive margin setting after 750 Ma and before the emplacement of the Nersa magmatic complex. The upper part of the stratigraphic succession (Oselok Group) consists of Cryogenian and Ediacaran glaciogenic deposits and associated cap carbonates, overlain by mid to late Ediacaran sequences of dominantly shallow-marine and fluvial siliciclastic rocks. Provenance data indicate that rocks from the Tuva-Mongolia and Zavkhan terranes provided a significant input of detrital material into the sedimentary basin that was the source of the glacial deposits. Orogenic processes during the late Ediacaran (ca 570–540 Ma) in Eastern Sayan were likely associated with the accretion of the Tuva-Mongolia terrane, as indicated by the detrital zircon data. [ABSTRACT FROM AUTHOR]

The paper presents data on the granitoids of the Yurubchen massif, which make up the basement of the Kamov arch, Baikit uplift in the western part of the Tunguska superterrane of the Siberian craton. Rocks of the massif were recovered by drillholes from depths of 1.8–2.0 km and occupy an area of at least 400 km2. The U–Pb (SHRIMP) zircon age, geochemistry, and isotopic features of rocks of the Yurubchen massif indicate that it comprises granitoids of two groups, which are coeval but spatially separated from one another and differ in petrogenetic characteristics. The granodiorites (2562 ± 16 Ma) have εNd(T) = + 0.9 to +2.1, contain high LREE concentrations, show highly fractionated HREE patterns (GdN/YbN = 3.4–6.2), which could be formed via partial melting of an enriched mafic source with a short crustal history at a depth of at least 45 km, in equilibrium with garnet-bearing residue. In contrast to the granodiorites, the sodic and potassic leucogranites (2563 ± 10 and 2563 ± 18 Ma, respectively) with εNd(T) from –0.3 to –1.7 and less fractionated HREE patterns (GdN/YbN = 1.7–2.3) could be produced by melting a crustal source at shallower depths. Isotopic data on the rock-forming and accessory minerals point to ca. 2.40 Ga (Rb–Sr and Sm–Nd mineral isochrones) and ca. 1.87 Ga (Ar–Ar, biotite) episodes in the postmagmatic history of the Yurubchen massif. The synchronous generation of petrogenetically different granodiorites and leucogranites may be explained by postcollisional lithosphere extension at ca. 2.56 Ga, which resulted in the melting of heterogeneous crustal material of different age at various depths. The closure of the Rb–Sr and Sm–Nd systems at ca. 2.40 Ga was probably related to the termination of the evolution of the Neoarchean collisional orogen and the cooling of the Yurubchen massif to a temperature of ca. 400°C at a depth of 7–10 km. The later episode at ca. 1.87 Ga could be related to the tectonic exhumation of the Archean rocks in the western Tunguska superterrane during the development of the Paleoproterozoic Angara belt. In terms of the stabilization of the Archean continental crust, which was marked by ca. 2.56 Ga postcollisional granitoids, the Tunguska superterrane is younger than the terranes attributed to the Archaean Vaalbara and Superia supercratons but is comparable to crustal blocks in the Slavia supercraton and, perhaps, is a tectonic fragment of this youngest Neoarchean continent. [ABSTRACT FROM AUTHOR]

Comprehensive studies of peridotitic xenoliths from the Udachnaya kimberlite (Yakutian diamond province, Siberian craton) confirm that garnet shows inverse correlation of its volumetric percentage with its Cr2O3 contents in refertilizated peridotites, but no such correlation is observed in depleted peridotites. The correlation relationship plots as an isosceles hyperbola, which is consistent with the existing knowledge of origin of refertilized peridotite. The bulk content of aluminum is proportional to the garnet percentage both in depleted and refertilized peridotites, but Al2O3 in the rock correlates with Cr2O3 in garnet only in the refertilized varieties, while the two parameters are independent in depleted mantle rocks. According to the modeling of refertilization-related composition changes in the Udachnaya peridotites, garnet percentages are directly proportional to the amount of clinopyroxene (Gnt = 0.879*Cpx + 0.022, R2 = 0.78) and inversely proportional to that of olivine (Gnt = 0.026/Ol3.141, R2 = 0.79). As the shares of Gnt and Cpx increase from minimum values, orthopyroxene first increases (to 0.16) and then decreases since 0.65 Ol, 0.09 Cpx, and 0.10 Gnt. This model can constrain the place of the parent rock in the refertilization series knowing Cr2O3 contents in separate garnet grains. The average refertilization degree of lithospheric mantle in the region estimated from the compositions of more than 800 garnet xenocrysts in the Udachnaya kimberlite is expressed in the rock modal composition as: Ol = 0.72, Opx = 0.15, Gnt = 0.07, and Cpx = 0.06 (median values). [ABSTRACT FROM AUTHOR]

The paper presents data on garnets from serpentinized peridotite xenoliths in the Nyurba and Botuoba kimberlite pipes of the Nakyn kimberlite field. The major and trace-element compositions of the garnets were analyzed to determine their compositional specifics and genesis. Based on the REE content and chondrite-normalized distribution patterns, the garnets are divided into two types with sinusoidal ((Sm/Er)n > 1) and normal ((Sm/Er)n < 1) REE distribution patterns. In terms of the Y, Zr, Ti, and Eu relations, and the shape of REE distribution pattern, all the garnets correspond to garnets of metasomatized peridotites, except for one sample falling into the field of depleted garnets of harzburgite–dunite paragenesis. The geochemical characteristics of the garnets record two types of metasomatic agents: carbonatite/fluid for type 1 garnets and silicate/melt for type 2 garnets. The carbonatite metasomatic agent produced harzburgitic garnet and its further transformation into lherzolitic garnet. Silicate metasomatism, which led to the formation of the REE pattern of type 2 garnets, likely overprinted two different types of garnets and, respectively, gave two evolutionary trends. These are depleted residual garnets and type 1 garnets previously subjected to carbonatite metasomatism. The low Y and Th contents in combination with the low Ti/Eu ratios in garnets suggest a moderate reworking of lithospheric peridotites by silicate melts, which is consistent with the high diamond grade of the Nakyn kimberlite field. [ABSTRACT FROM AUTHOR]

• Zircons from studded crustal xenoliths do not record the age peak at 1.9 Ga. • Sodalite was found in mafic granulite xenoliths of the Yakutian kimberlite province. • Superplumes triggered the crustal growth and reworking at 2.7 and 1.9 Ga. • There is no collision zone between the Daldyn and Markha terranes. The tectonic framework of the Siberian craton is still under debate. It is generally assumed that the Markha and Daldyn terranes collided at 2.2–2.1 Ga and the final assembly of the Siberian craton occurred at 1.9–1.8 Ga. However, previous study on zircons from xenoliths of the Zapolyarnaya pipe, which is located in the Upper Muna kimberlite field and close to the boundary between the Markha and Daldyn terranes, do not show tectonothermal evidence younger than 2.7 Ga. To clarify the tectonothermal evolution of the Siberian craton, we present U-Pb ages and Hf isotope data of zircons from crustal xenoliths in the Novinka and Komsomolskaya Magnitnaya kimberlite pipes in the Upper Muna field. The zircon ages confirm only one major tectonothermal event at 2.7 Ga in the Upper Muna field, which doubts the existence of the collision zone between the Markha and Daldyn terranes. The middle-lower crust beneath the Upper Muna field is mainly composed of mafic and intermediate granulites and experienced long-term cooling. The negative values of ε Hf (2.7) suggests ignorable addition of juvenile component during partial melting of the Paleoarchean crust at 2.7 Ga. Compared with crustal xenoliths from other kimberlite pipes in the Yakutian diamondiferous province, the crust of the Anabar province shows vertical and lateral heterogeneity and the absence of a relationship between the crustal reworking degree and the main collision zones. We propose that the widespread 2.7 and 1.9 Ga tectonothermal events in the Anabar tectonic province were associated with the episodic rise of superplumes, which not only caused the crustal growth and reworking but also facilitated collision and amalgamation of terranes. [ABSTRACT FROM AUTHOR]

We present new geochronological data on dolerites from the Chaya dyke swarm of the Baikal inlier of the Siberian craton. The U‐Pb dating of baddeleyite from one dyke located at the SW end of the Chaya dyke swarm yielded an age of 1752±6 Ma, similar to the previously obtained age of a dyke in the NE end of this swarm. These ages estab‐ lish an age of 1752 Ma for a unified Chaya dyke swarm that extends for more than 200 km in the Baikal inlier of the Siberian craton. These new data confirm that the entire Chaya dyke swarm (as well as the Timpton‐Algamay and Eastern Anabar swarms) is a part of an overall radiating dyke swarm belonging to the Late Paleoproterozoic Timpton Large Igneous Province (LIP), the center of which is located in the middle section of the Vilyuy river flow. Thus, the LIP is enlarged to include the area further west in the Siberian craton.

We have studied variations in the structure and composition of minerals from the pipes of the Yakutian kimberlite province (YKP) in different mantle terranes of the Siberian craton. The study was based on an extensive database, including the microprobe analysis datasets consolidated by IGM, IG, IEC and IGDNM SB RAS and ALROSA and geochemical analysis of minerals performed by LA‐ICP‐MS (Laser Ablation Inductively Coupled Plasma Mass Spectrometry). The reconstruction shows layering under the tubes, including 6–7 slab that were probably formed due to subduction; the slabs are separated by pyroxenitic, eclogitic and metasomatic layers and dunite lenses. Transects and mantle profiles across kimberlite fields are constructed. Within the limits of the revealed tectonic terranes, we assume a collage of microplates formed in the early – middle Archean. Extended submeridional structures of the tectonic terranes are not always confirmed at the mantle level. Beneath the Anabar and Aldan shields, the mantle sections show more coarse layers and 3–4 large horizons of dunites with garnet and pyroxene nests separated by ilmenite‐ phlogopite metasomatites and pyroxenites. Terranes representing the suture zones between the protocratons (e.g. Khapchan) are often saturated with eclogites and pyroxenites that may occur as leghthy ascending bodies of magmatic eclogites penetrating through the mantle lithosphere structure (ML). A nearly ubiquitous pyroxenite layer at the level of 3.5–4.5 GPa formed probably in the early Archean with a high heat flux during melting of eclogites and was subsequently traced by plume melts. Within the early Archean protocratons – granite‐greenstone terranes (Tungus, Markha, Berekta, and Sharyzhalgai, ~3.8–3.0 Gyr [Gladkochub et al., 2019], the mantle lithosphere is less depleted and largely metasomatized. The ML structure of the Daldyn and Magan granulite‐orthogneiss terranes is layered with folding revealed in the north‐to‐south sections from the Udachnaya pipe to the Krasnopresnenskaya pipe, which is less pronounced in the latitudinal direction. From the Daldyn field to the Alakit field, there is an increase in the degree of metasomatism, and higher alkalinity of pyroxenes and larger amounts of phlogopite are noted. The most productive Aikhal and Yubileinaya pipes are confined to a dunite core, which is accompanied by a change in the specialization of high‐charge elements Ta‐Nb to Zr‐Hf. Within the limits of the Magan terrane, the thin‐layer structure of the middle and upper parts of the craton keel is replaced with a sharply depleted productive horizon at its base. The mantle of the granite‐greenstone Markha terrrein comprises eclogite (often pelitic) horizons, which suggests subduction of the continental lithosphere or sediments. In the central and northern parts of the Siberian craton, most structures in the mantle are sinking to the west at small angles. The geochemistry features of garnets and pyroxenes from various mantle terranes are considered in detail.

Granitoids of the Uda complex are distributed within the southeastern marginal part of the Siberian craton and its folded framing. Geochemical, isotope (Nd, Sr), and geochronological (U–Pb ID TIMS) studies of two massifs (Chalbuk-Yakon and Uyan-Tavitchak) of this complex of the Dzhugdzhur Block of the Stanovoy suture were carried out; the results are presented in this paper. It is found that formation of these massifs took place in the Early Cretaceous (116 ± 1 Ma) in the geodynamic setting of lithospheric extension. The initial magma for these granitoids was formed from a mixed source: Early Precambrian lower crust and mantle, with a clear predominance of the crustal component. The granitoids of the Uda complex of the Dzhugdzhur block most likely represent the eastern end of the Udsko-Zeya (Stanovoy) post-collision magmatic belt, stretching for more than 1000 km along the southern framing of the Siberian craton parallel to the Mongol–Okhotsk suture zone and stitching various tectonic blocks of the northeastern part of the Central Asian fold belt. There is every reason to believe that, further to the west, the Udsko-Zeya (Stanovoy) belt passes into the West Transbaikal rift system, the formation of which took place in the interval of 170–110 Ma. In other words, it can be assumed that in the Mesozoic, in the southern framing of the Siberian craton, there was a giant unified rift system stretching for more than 2000 km. [ABSTRACT FROM AUTHOR]

The paper reports geochemical, geochronological (ID–TIMS zircon U–Pb) and isotope–geochemical (Nd, Pb) study of granitoids of the Kodar complex developed in the western part of the Aldan shield. It has been established that these rocks can be classified as postcollisional A–type rapakivi granites, which together with the mafic–ultramafic rocks of the Chinei complex compose a single magmatic association formed within 1876 ± 4–1859 ± 2 Ma. The massifs of this association are a part of the giant South Siberian magmatic belt over 2500 km in length, which was formed at the final stage (1.88–1.84 Ga) of evolution of the Paleoproterozoic orogen. Globally, this belt is the largest stitching suture, which marks the formation of the Siberian craton and its entrance into the Paleoproterozoic Nuna supercontinent. The formation of the initial magmas of the Kodar granitoids was related to the mantle–crustal interaction during the mixing of primary mafic mantle magmas or their derivatives with anatectic melts derived through partial melting of the Archean lower continental crust of the region under the thermal influence of mafic magma. The crustal component in the source clearly predominates and has a heterogeneous nature. The mantle component is mainly represented by ancient enriched mantle, with the possible contribution of the OIB–type component. [ABSTRACT FROM AUTHOR]

Sulfide-bearing polymineralic inclusions in mantle-derived chromium pyrope garnets of lherzolite paragenesis from lamprophyres of the Chompolo field (Aldan shield, southern Siberian craton) have been studied. The inclusions are composed of either only sulfides or sulfides in association with other minerals (carbonates, silicates, oxides, etc.). The sulfide part of the inclusions is represented by up to four minerals. Among the sulfides, minerals rich in Cu and Ni have been found, whereas Fe sulfides (pyrrhotite, troilite) are absent. This distinguishes the inclusions studied from the majority of sulfide inclusions in mantle minerals and diamonds, as well as in mantle xenoliths from kimberlites. The formation of polymineralic inclusions in chromium garnets of the Chompolo field is attributed to the effect of a carbonate–silicate metasomatic melt/fluid on mantle peridotites, as evidenced by the mineral suite associated with the sulfides. The research results indicate significant differences in the nature of metasomatic processes that occurred in the lithospheric mantle of the southern and central parts of the Siberian craton. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The petrographic, lithogeochemical and U-Pb (LA-ICP-MS) geochronological studies were carried out to investigate the terrigenous rocks sampled from the lower part of the Ipsit suite of the Karagass series (Sayan segment of the Sayan-Baikal-Patom belt). These rocks include sandstones, aleurite sandstones and aleurolites, and their mineral compositions are close to that of arkose. Most of the studied rock samples show petrographic features typical of the epigenetic changes at the stage of catagenesis: regeneration of quartz clastic grains, pelitization of potassium-feldspar clastic grains, occurrence of clay-hydromica aggregate, sericitization of plagioclase, chloritization of biotite, and silicification of dolomite pieces, and occurrence of authigenous tourmaline. The above was confirmed by the analysis of the concentrations of petrogenic elements in the studied rocks from the lower part of the Ipsit suite. The analysis results show that the concentrations of K2O are elevated, while the concentrations of Na2O are relatively very low, which may be due to the redistribution of these elements during epigenetic transformations. According to the classification by genetic types on the basis of the system of petrochemical modules, the rocks of the lower part of the Ipsa suite are of the petrogenic nature. The acidic igneous rocks are dominant in the source area, as evidenced by the presence of granitoid and quartzite fragments in the clastogenic component, as well as the set of accessory minerals typical of the igneous rocks of the acidic composition, and the distribution pattern of rare and trace elements. According to the U-Pb (LA-ICP-MS) dating of detrital zircons from the aleurite sandstone sampled from the lower part of the Ipsit suite, the zircons are exclusively of the Archean-Early Proterozoic ages. Such ages correlate with the age of the granitoids of the Sayan complex and the felsic volcanites from the Maltsev layer of the Elash series (Biryusa block). Furthermore, the detrital-zircon age spectra of the aleurite sandstone of the lower part of the Ipsit suite are identical to the detrital-zircon age spectra of the terrigenous rocks from the underlying strata of the Shangulezh and Tagul suites of the Karagass series. This study suggests that sedimentation of the Ipsit suite of the Karagass series took place due to the influx of detrital material from the southern part of the Siberian craton into the sedimentation basin, and the acidic igneous rocks of the Biryusa block were one of the main sources of detrital material.

The article reports on the geological, mineralogical, geochemical and isotope-geochemical studies of granitoids (charnockites) from the Tatarnikovsky massif located in the northern part of the Baikal uplift of the Siberian craton basement. The age of the studied granitoids is 1.85 Ga. Like other unmetamorphosed granitoids and associated volcanic, the granitoids dated 1.88–1.84 Ga are abundant in the southern area of the Siberian craton. These rocks are a part of the South Siberian post-collisional magmatic belt. The Tatarnikovsky granitoids form a series of small massifs confined to the Davan tectonic zone. However, unlike the rocks of the Davan zone, these granitoids have not been subjected to dynamometamorphism, mylonitization and metasomatism, and seem younger than the geologic structure of this zone. The formation of granitoids coincides in time with the youngest formations in the North Baikal volcanoplutonic belt (1.85–1.84 Ga). The Tatarnikovsky granitoids have two facies varieties – coarse-grained and medium-fine-grained porphyric, the transition being gradual. Considering the mineral composition of the granitoids, specifically the presence of orthopyroxene, these rocks can be classified as charnockites. The research results presented in this article are based on the study of charnockites in the Tatarnikovsky massif, the largest in the Tatarnikovsky complex. The chemical composition of the Tatarnikovsky coarse-grained granitoids corresponds to monzonite and syenite, and fine-grained porphyry granitoids are granosyenite. All the studied granitoids are close to alkaline and calc-alkaline, metaluminous (ASI=0.83–0.97), ferrous (FeO*/(FeO*+MgO)=0.86–0.89) granite, with high concentrations of Nb, Y, Zr, and Ba, and low concentrations of Sr. According to their geochemical characteristics, the Tatarnikovsky granitoids correspond to A-type granite. These rocks show negative values εNd(t)=–1.4…–3.5 and model age ТNdDM=2.4–2.5 Ga. The temperature estimated for the initial stages of crystallization of granitoid melts suggests that granitoids formed at high temperatures, 890–960°С (i.e. the zircon saturation temperature). The granitoid melts crystallized in hypabyssal conditions at the pressure of 2.2–2.9 kbar, as well as in conditions of low or moderate oxygen fugacity. According to the mineralogical, geochemical and isotope-geochemical data, the Tatarnikovsky charnockite could have resulted from melting of mafic rocks from the lower crust (gabbroid, and ferrodiorite) which are products of differentiation of the tholeiitic mantle magmas that had intruded into the base of the continental crust. Taking into account the high concentrations of Ba and the positive anomalies of Eu in the distribution spectra of rare-earth elements (REE) of the coarse-grained granitoids, it can be suggested that these granitoids are the products of partial melting of the crustalmafic source. The fine-grained porphyry granitoids with higher silica contents and lower Ba and Zr contents than those in the coarse-grained granitoids, as well as the negative anomalies of Eu in the REE distribution spectra, are the products of fractional crystallization of the granitoid melt. With regard to formation of the unified structure of the Siberian craton, the geodynamic setting for formation of the Tatarnikovsky charnockite is considered as postcollisional extension due to the fact that these rocks belong to the South Siberian post-collisional magmatic belt. However, on a more local scale of the Baikal uplift of the Siberian craton basement, we suggest that the intercontinental rifting setting was in place during the intrusion of the Tatarnikovsky granitoids, the rocks of the North Baikal volcanoplutonic belt, the granitoids of the Primorsky and Achadsky complexes that cross the rocks of the Akitkan fold belt, collision events in which ceased 1.98–1.97 Ga ago.