Calcic garnet is a common component of skarns, alkaline igneous rocks and carbonatites. Recent studies report garnet laser ablation-ICP-MS U-Pb ages ranging from ca. 20 to 3100 Ma demonstrating the advantages of garnet for U-Pb geochronological studies. However, calibration using well-characterised matrix-matched reference materials is a critical issue for accurate age determinations. In this study we present the major and trace element compositions, and U-Pb systematics obtained from isotope dilution-TIMS and LA-ICP-MS measurements for Kovdor (Kovdor-GRT) andradite-shorlomite-morimotite garnet (Kola Alkaline Province, Kola Peninsula) as a potential reference material for LA-ICP-MS U-Pb dating. ID-TIMS gave 206Pb/238U, 207Pb/235U and 207Pb/206Pb Pbc-corrected weighted mean ratios of 0.06008 +/- 0.00018 (2s, MSWD = 4.5), 0.4495 +/- 0.0013 (2s, MSWD = 1.6) and 0.0542 +/- 0.0006 (2s, MSWD = 0.001), respectively. The weighted mean 206Pb/238U age is 376.50 +/- 0.9 Ma (MSWD = 1.3), the 207Pb/235U age is 376.5 +/- 0.62 Ma (MSWD = 0.83) and the 207Pb/206Pb age is 380.6 +/- 1.7 (MSWD = 0.27). The Concordia age of 376.6 +/- 0.86 Ma (MSWD = 0.79) for Kovdor-GRT, determined by ID-TIMS, is interpreted as the best estimate for its crystallisation age. The low common Pb (Pbc) content (Pbc/Pbt varies from 0.05 to 0.08), moderate U mass fraction (12.4-33.0 mu g g-1) and isotopically homogeneous composition allowed meaningful 206Pb/238U age determinations using various LA-ICP-MS systems. LA-ICP-MS measurement results are characterised by precisions fit for purpose and yield consistent 206Pb/238U ages indistinguishable from those obtained by ID-TIMS. The results highlight the potential of Kovdor garnet as a reference material for in situ U-Pb dating.

Spatiotemporal variations in magmatic compositions reflect changes in magma sources and their formation conditions, offering insights into geodynamic processes. This study presents new zircon U-Pb and geochemical data for early-mid Paleozoic granitoids in northern Beishan, located within the southern Central Asian Orogenic Belt. Late Ordovician (451 Ma) granodiorites are I-type and formed through water-fluxed melting of amphibolites. Early Devonian (403-397 Ma) granites show I-, S-, and A-type affinities with enriched Sr-Nd isotopes, indicating ancient crustal sources. Late Devonian to early Carboniferous (366-357 Ma) granitoids exhibit I-type characteristics. They and coeval intermediate-felsic intrusives show similar Sr-Nd-Hf isotopes, with Sr-87/Sr-86((i)) from 0.7045 to 0.7075, epsilon(Nd)(t) from -2.93-0.92, and zircon epsilon(Hf)(t) predominantly ranging from 2.9 to 6.5. Geochemical studies suggest their derivation from metasomatized mantle, with fractional crystallization playing a key role. Available data reveal three magmatic stages: similar to 500-420 Ma, similar to 420-390 Ma, and similar to 370-350 Ma. Stage I mainly consists of (quartz) diorites, granodiorites, and granites. They show increasing K2O/Na2O and zircon saturation temperatures from south to north, with the Hanshan unit characterized by A-type granites. These variations reflect northward subduction of the Beishan Ocean, leading to water-fluxed crustal melting in the Mazongshan arc and dehydration melting in the Hanshan back-arc. In Stage II, complex mafic-felsic rock associations composed of (quartz) diorites, high-silica granites, gabbros, and intermediate-mafic volcanic rocks, along with high temperatures required for S- and A-type granite formation, suggest increased mantle heat input from slab breakoff following Beishan Ocean closure. Stage III rocks, confined to the Mazongshan unit, consist of diorites, tonalites, granodiorites, and granites associated with southward subduction of the Jijitaizi-Xiaohuangshan Ocean. This study demonstrates that multistage subduction-accretion contributed to Beishan orogen formation, highlighting magmatic compositional variations as key to understanding accretionary orogens.

On one hand, heavy minerals of terrigenous rocks make it possible to obtain unique information on configuration of the direction of clastic sediment transport into the basin and on the other to reconstruct the time for erosion of petrocomplexes of the provenances. In order to reconstruct the paleogeographic setting of the Southern Cis-Urals and the orogenic evolution of the Paleo-Urals at the Permian-Triassic boundary, the authors evaluated the composition and stability of the provenances for the Permian-Triassic terrigenous rocks of the Boevaya Gora section (Orenburg region) based on the analysis of the heavy minerals – zircon and garnet. Heavy mineral samples were taken from sandstones of three stratigraphic levels: Upper Permian, Lower Triassic, and paleontologically barren interval in the immediate vicinity of the Permian-Triassic boundary. The results of U-Pb LA-ICP-MS dating of detrital zircon and analysis of garnet end-members proportions have shown that the provenances covered the petrocomplexes of the tectonic zones of the Ural foldbelt – Uraltau, Main Uralian fault and Magnitogorsk, which allows reconstructing the Paleo-Urals orogen main-watershed axis position at the Permian-Triassic boundary east of that of the present day. It is shown that the source areas near the Boevaya Gora section remained stable during the whole time of accumulation of the studied part of the section. This conclusion is confirmed by the results of measuring the anisotropy of magnetic susceptibility in the studied rocks, which also suggest the strengthening of hydrodynamic regime in the terminal Permian and predominantly meridional direction of the clastic sediment transport.

The Vitim volcanic field, comprising Cenozoic basaltic lava flows associated with the Baikal Rift volcanism, contains abundant mantle xenoliths that offer insights into the subcontinental lithospheric mantle (SCLM) beneath the region. This study investigates the mineralogical and geochemical compositions of these mantle xenoliths, entrained in Miocene and Pleistocene basalts. The xenoliths, predominantly garnet-, spinel-, and garnet-spinel-bearing lherzolites, exhibit high modal content of clinopyroxene and low fosterite content of olivine, suggesting a relatively fertile SCLM. Distinct variations in CaO and Al2O3 observed in spongy rims and cores of clinopyroxenes likely result from decompression-induced partial melting. Trace element patterns of clinopyroxene reveal three types: light rare-earth elements (LREE) depleted, LREE enriched, and transitional LREE types. Whole-rock trace element compositions of the four Vitim lherzolites showing flat to LREE and large ion lithophile elements enrichments are entirely consistent with those of their clinopyroxenes. The LREE depleted type indicates that these lherzolites were residual mantle after melt extraction, whereas the LREE enriched type suggests that they were metasomatized after residual mantle formed by partial melting. The transitional LREE type showing in-between features among the above two end-members could represent that those lherzolite underwent less or incomplete metasomatism, thus clinopyroxene cores still retain primary depleted LREE type feature of residual mantle. Most Vitim lherzolites were affected by cryptic metasomatism with less stealth metasomatism, whereas only those with secondary amphibole and apatite could be influenced by modal metasomatism. The lithospheric mantle beath the Vitim volcanic field representing by these lherzolites was metasomatized predominantly by hydrous fluids with minor silicate melts. Using the clinopyroxene melting model, it was found that most Vitim lherzolites have experienced <10% partial melting. Geothermal gradients estimated from mineral geothermobarometry indicate that lherzolites in the Pleistocene basalts equilibrated at shallower depths with higher temperatures compared to those in the Miocene basalts with deeper depths and lower temperatures. SrNd isotopic ratios, combined with previous results (Ionov et al., 2005), demonstrate that the Miocene lherzolites have a broader range from depleted to enriched components, whereas lherzolites in the Pleistocene basalts show lesser enrichment. It is proposed that the Pleistocene basalts captured shallower SCLM lherzolites experienced less degrees of melt metasomatism than those deeper SCLM lherzolites hosted by Miocene basalts. Considering the deeper SCLM is more vulnerable to metasomatism by ascending melts, such temporal and geochemical variation further emphasizes progressive asthenosphere upwelling beneath the Vitim region from the Miocene to Pleistocene time.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X2305015X

Dating of magmatic rocks from paleo-island arcs of orogenic belts helps to define the precise timing of subduction processes that took place during the formation of the orogen. Within the central (East Trans-Baikal) part of the Mongol-Okhotsk orogenic belt, the Kamensk island-arc terrane is an example of such paleo-island-arc complex. Its intrusive part is included into the Bereinsky complex, represented by a gabbro-diorite-tonalite-plagiogranite series of rocks demonstrating subduction geochemical characteristics. The dating of zircons from acidic rocks of this complex by the U–Pb classical method showed that they were produced in a narrow time interval – 203±1–205±1 Ma, which corresponds to Norian/Rhaetian boundary of the Late Triassic. Taking into account the previously obtained age of the diorites (254±5 Ma), the timing of formation of the entire series of intrusive rocks is about 50 Ma, thus indicating in the Late Permian – Late Triassic the subduction along the northern (in modern coordinates) margin of the Mongol-Okhotsk Paleocean beneath the Siberian paleocontinent. Diorites of the first phase have positive values ɛND(254MA) = 3.2–3.6 (TNd(DM) = 879–994 Ma), and plagiogranites – ɛND(205MA) = 2.3–3.5 (TNd(DM) = 859–1028 Ma), which points to the connection of these rocks with the substance of the depleted mantle source and is consistent with the Sm-Nd isotope characteristics of the juvenile crust of the Central Asian orogenic belt. This study was supported by Russian Science Foundation, grant no. 22-27-00775. The resources of the Shared Use Center for Isotope-Geochemical Research (Vinogradov Institute of Geochemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk) were used in this work.

Dating of igneous rocks from paleo-island arc complexes of orogenic belts makes it possible to determine the precise timing of subduction processes that occurred during the formation of the orogen. Within the central (East Transbaikal) part of the Mongol–Okhotsk orogenic belt, the Kamenka island-arc terrane is an example of such a complex. Its intrusive part is included into the Bereya complex, represented by a gabbro-diorite-tonalite-plagiogranite series of rocks demonstrating subduction geochemical characteristics. The dating of zircons from acidic rocks of this complex by the U–Pb classical method showed that they were formed in a narrow time interval of 203 ± 1–205 ± 1 Ma, which corresponds to the Norian–Rhaetian boundary of the Late Triassic. Taking into account the previously obtained age of the diorites (254 ± 5 Ma), the timing of formation of the entire series of the intrusive rocks is about 50 Ma, thus indicating the probable subduction along the northern (in modern coordinates) margin of the Mongol–Okhotsk Paleocean under the Siberian paleocontinent in the Late Permian – Late Triassic. The diorites of the first phase have positive values of εND(254 Ma) = 3.2–3.6 (TNd(DM) = 879–994 Ma), and the plagiogranites have ɛND(205 Ma) = 2.3–3.5 (TNd(DM) = 859–1028 Ma), which points to the relationship between these rocks and the substance of the depleted mantle source and is consistent with the Sm–Nd isotope characteristics of the juvenile crust of the Central Asian orogenic belt.

Results of the study of miaskite syenites of the Lovozersky massif, pulaskites of the Khibiny massif and rocks of the larvikite-lardalite series of the Khibiny massif, as well as subalkaline volcanics preserved as remnants in their roof are presented. The studied rocks are characterized by a low agpaitic coefficient 1, by the absence of typical minerals of ultra-alkaline rocks (eudialyte, enigmatite, etc.) as well as by the presence of zircon. The morphological features and chemical composition of zircon from the Lovozero massif miaskite syenite indicate magmatic origin of the massif, allowing to determine the age of crystallization of miaskites at 373 ± 5 Ма. The isotope-geochemical characteristics of the rocks of the subalkaline series indicate the mantle origin of the Lovozero massif miaskites, the absence of signs of crustal contamination in them and their formation during the evolution of the ankaramite melt. The formation of the pulaskites of the Khibiny massif, which occurred according to a similar scenario, was complicated by the assimilation of crustal material, proportion of which, according to the model calculations, did not exceeded ten percent.

The results of U–Th–Pb (LA–ICP–MS) geochronological studies of detrital zircon from the Quaternary sands of the Tokko Basin on the eastern flank of the Baikal Rift Zone are reported. It is shown that their main sources were Mesoarchean tonalite–trondhjemite orthogneisses and metavolcanics, as well as Meso- and Neoarchean syn- and post-collision granitoids of the Charа–Olekma geoblock of the Aldan Shield, which are located near the Tokko Basin. Moreover, the input of sedimentary material into the basin could have occurred during the melting of glaciers that covered the Udokan Ridge to the south and the Kodar Ridge to the north in the Middle–Upper Quaternary.

The paper discusses possible immiscibility between fluoride salt (“cryolite”) and silicate liquids into which the parental melt of the Katugin massif exsolves, and the petrological implications of this phenomenon. Results of a detailed study of the cryolite and zircon are presented. Liquid immiscibility is demonstrated to have triggered the massive crystallization of zircon and, together with the processes of subsequent evolution of the cryolite melt, contributed to the formation of the large cryolite bodies. Data on mineral-hosted inclusions were used to estimate the crystallization temperatures of fluoride salt and silicate melts and outline the pathways of their evolution during the formation of the massif. It is shown that the granites of the Katugin and West Katugin massifs were most likely derived from distinct sources, that differed mainly in fluorine content. Data on the chemical composition of three zircon generations identified in the granites of the Katugin massif are presented.

The paper presents the results of geochemical and Sm-Nd isotopic-geochemical studies of metavolcanic rocks of the Djagdagle formation of the northwestern part of the Bureya continental massif. As a result of reconstruction of the primary composition of the metavolcanic rocks, the correspondence of their protoliths to the pantelleritic, comenditic rhyolites is shown. Nd-features of metavolcanic rocks of the Djagdagle formation indicate the melting of rocks of continental crust with Paleoproterozoic model ages during the formation of their initial melts. Geochemical features, close spatial position with Mongol-Okhotsk orogenic belt allow us to link the formation of initial melts of metavolcanic rocks of the Djagdagle formation with within-plate magmatism in the rear zone of subduction of the Mongol-Okhotsk Ocean beneath the northern (in modern coordinates) margin of the Bureya continental massif.

The paper presents the results of U-Th-Pb (LA-ICP-MS) geochronological studies of detrital zircon from Quaternary sands of the Tokko basin on the eastern flank of the Baikal rift zone. The study shows, that their main sources were Mesoarchean tonalite-trondhjemite orthogneisses and metavolcanics, as well as Meso- and Neoarchean syn- and post-collision granitoids of the Charа-Olekma geoblock of the Aldan shield, which are located near the Tokko basin. Moreover, the supply of sedimentary material into it could have occurred during the melting of glaciers that covered the Udokan Uplift in the south and the Kodar Uplift in the north in the Middle-Late Quaternary.

Sviatonossites are syenites with andradite garnet, a rare type of igneous rocks described by P. Eskola in 1913 on the Svyatoi Nos Peninsula (Lake Baikal). Due to the absence of zircon in the rocks, which makes it possible to date them reliably by the U‒Pb method, geochronological Sm–Nd studies of the bulk composition and minerals are carried out. As a result, two estimated periods of the formation of sviatonossites are obtained. According to the bulk composition and four minerals (garnet, pyroxene, potassium feldspar, and apatite), the age is 262 ± 21 Ma (RMSD = 1.6), and according to the bulk composition and garnet, it is 274 ± 25 Ma (RMSD = 0). The results obtained coincide with the timing of tectonic–metamorphic and igneous processes associated with the formation of the Eastern Transbaikalia segment of the Central Asian (Mongol–Okhotsk) folded belt. Sviatonossites in the complexes of mobile (folded) belts framed by the Siberian Craton are indicator rocks reflecting the manifestation of mantle–crustal interaction.

Geochronological (U-Pb on zircons, ID-TIMS), isotope-geochemical (Nd, Sr, Pb), and geochemical studies of rocks of the Amanan and Amudzhikan intrusive complexes and volcanic rocks of the Ukurey Suite in the eastern part of the West Stanovoy superterrane of the Central Asian Fold Belt were performed. The belonging of granitoids of these complexes to high-potassium C-type adakites is substantiated. The cogeneticity of the studied rocks has been established, which makes it possible to unite them into one Amudzhikan volcano-plutonic association formed in the age range of 133±1–128±1 Ma. The igneous complexes of this association are part of the Stanovoy volcano-plutonic belt, which extends in the sublatitudinal direction from the Pacific Ocean deep into the North Asian continent for more than 1000 km subparallel to the Mongol-Okhotsk suture zone and stitches the tectonic structures of the Dzhugdzhur-Stanovoy and West-Stanovoy superterranes. The formation of the Stanovoy Belt is connected with the closure of the Mongolo-Okhotsk Ocean and the collision of the continental masses of the North Asian and Sino-Korean continents at the turn of ~140 Ma. The subsequent collapse of the collisional orogen, accompanied by large-scale lithospheric extension and delamination of the lower part of the continental lithosphere, led to upwelling of the asthenospheric mantle. This caused the melting of the lithospheric mantle and continental crust and, as a consequence, the formation of both mafic melts of the shoshonite type and anatectic crustal melts of the adakite type. The mixing of these melts led to the formation of the parent magmas of the Amudzhikan magmatic association. The crustal component in the source was of a heterogeneous nature and was finally formed as a result of the Early Cretaceous collision event. It is characterized by upper-crustal isotopic parameters: an increased Rb/Sr and U/Pb ratio and a decreased Sm/Nd ratio in the source. The mantle component is represented by the material of the enriched lithospheric mantle of the Central Asian fold belt, the formation of which is associated with subduction processes at the stage of closure of the Mongol-Okhotsk paleoocean. Metasomatic transformation of the mantle with the introduction of melts and fluids with isotopic parameters of an EMII-type source or upper crust occurred at this stage.

Geochemical, geochronological (U–Pb zircons, ID-TIMS) and isotope-geochemical (Sm–Nd) studies of the rocks of the Bambukoy volcano-plutonic association, which form the Zhanok-Bambukoy volcano-tectonic structure within the Anamakit–Muya terrane on the northern flank of the Barguzin–Vitim superterrane of the East Transbaikalian segment of the Central Asian orogenic belt. The association includes volcanic rocks of the Zhanok Suite (dacites and rhyolites mainly), as well as leucocratic and biotite granites of the Bambukoy Complex that cut through them. The granites of this complex host the Mokhovoe tin deposit, which is attributed to the tin-porphyry formation. Subvolcanic rocks of the Zhanok Suite are considered as ore-bearing. The geochemical features of the volcanic rocks of the Zhanok Suite and the granites of the Bambukoy complex bring them closer to S-type granites, and belonging to a single tin-bearing Bambukoy volcanic-plutonic association. The formation of this association is determined by the age interval 834 ± 23–818 ± 7 Ma. The isotopic data point to a source of parental magmas from the rocks of the Bambukoy volcano-plutonic association, formed as a result of mixing of the material of two crustal sources, the mature Early Precambrian and the juvenile Early Baikal. The geochemical data also point to an exclusively crustal source of the rocks of this association. Thus, the Bambukoy tin-bearing volcano-plutonic association was formed in the Neoproterozoic time (Tonian), most likely under lithospheric extension conditions due to a source with a complex and long crustal prehistory.

The results of geochemical and Nd isotopic studies of rocks and U–Th–Pb (LA-ICP-MS) geochronological and Hf isotopic studies of detrital zircon from metaterrigenous rocks of the Kodar Group of the Udokan Complex (Aldan Shield) are presented. It is established that the age of rocks of the Kodar Group is 1.99–1.91 Ga, whereas the age of rocks of the Chinei and Kemen groups of the Udokan Complex is 1.90–1.87 Ga (Kovach et al., 2018, 2023a). This allows us to raise the issue of recognition of the Kodar Group as an independent stratigraphic subdivision. The terrigenous rocks of the group were sourced from the Archean igneous and metamorphic rock of the Chara–Olekma Geoblock and probably the Kalar and Kurulta blocks of the Stanovoi suture zone, as well as the Paleoproterozoic (2.04–1.99, 2.08, 2.20, and 2.30 Ga) complexes of active continental margins or ensialic island arcs in the western–northwestern and southern (in the present-day coordinates) frame of the Chara–Olekma Geoblock, which are unidentified in the region at the current erosion level. Erosion of rocks of magmatic arcs and the continental slope led to the deposition of rocks of the Kodar Group in a retroarc foreland basin, whereas further collapse of the orogen and the formation of an intracontinental extension basin were responsible for the deposition of terrigenous rocks of the Chinei and Kemen groups. The obtained data indicate widespread previously unidentified Paleoproterozoic continental crust formation at about 2.04–1.97 Ga in the western part of the Aldan Shield.

The paper presents the results of U–Pb (ID-TIMS) geochronologic, geochemical, Sm–Nd isotopic-geochemical studies of metavolcanic rocks of the Djagdagle formation, which are among the key elements in the structure of the Bureya continental massif. It was established that the age of metavolcanic rocks of the Djagdagle formation is 217 ± 7 Ma and corresponds to the Late Triassic. This fact contradicts the traditional ideas, according to which the Early Precambrian age is attributed to the Djagdagle formation. The results of Sm–Nd isotope studies of the considered metavolcanic rocks indicate the melting of rocks of continental crust with Paleoproterozoic model ages during the formation of their initial melts. The new geochronologic data and previously published data allow us to distinguish at least two stages of magmatic activity in the Triassic within the northwestern part of the Bureya massif ~243 and 219–201 Ma. On the basis of synchronous manifestation of Neoproterozoic, Early Paleozoic, Late Paleozoic and Early Mesozoic magmatic events in the history of geologic development of the Bureya and Songnen– Zhangguangcai Range massifs, an assumption about their common geological history at least since the Late Neoproterozoic has been put forward. The close spatial position of metavolcanic rocks of the Djagdagle formation with Mongol–Okhotsk orogenic belt, their Late Triassic age (217 ± 7 Ma) and geochemical features allow us to link the formation of initial melts of metavolcanic rocks of the Djagdagle formation with within-plate magmatism in the rear zone of subduction of the Mongol–Okhotsk Ocean beneath the northern (in modern coordinates) margin of the Bureya continental massif.

--We carried out a detailed geological, geochronological, geochemical, and isotope study of diorites from a dike located in the central part of the Baikal uplift of the Siberian craton. The geochemical and isotope data obtained for diorites of the studied intrusion were compared with coeval mafic and intermediate igneous rocks of the southern part of the Siberian craton. The U-Pb (ID-TIMS) baddeleyite age of 1862 +/- 7 Ma has been estimated for diorite from a dike located in the area of the Onguren Village. The obtained data are the first reliable age determination for the Paleoproterozoic mafic and intermediate igneous rocks of the Baikal uplift, which are part of the South Siberian postcollisional magmatic belt. The dike is of NE strike. The dike rocks correspond in chemical composition to diorites and are highly differentiated varieties (mg# = 36.5-37.4). There are no significant variations in the composition of diorites in the marginal and central parts of the dike. The rocks are characterized by low contents of TiO2, P2O5, and Nb, high contents of Th, Zr, Ba, and LREE, and low negative values of epsilon Nd(T) (-5.9 to -6.2). We assume that the diorites formed from the enriched subcontinental lithospheric mantle. The obtained geochemical and isotope data show similar negative values of epsilon Nd(T) from -4.3 to -11.6 for most of Paleoproterozoic mafic and intermediate igneous rocks of the South Siberian postcollisional magmatic belt within the Aldan Shield, the Baikal uplift, and the Irkut block of the Sharyzhalgai uplift. These rocks correspond in geochemical features to rocks resulted from the melting of subduction-modified lithospheric mantle sources in the postcollisional extension setting at the final Paleoproterozoic stage of formation of the Siberian craton.

The palingenic calc-alkaline granitoid massifs of the Olekminsky complex form a magmatic belt stretching within the Western-Stanovoy terrane in the northeastern direction for more than 700 km. New U-Pb LA-ICP-MS dates for zircons from the granodiorites of the Marekta-Bereinsky massif of the Olekminsky complex and the granodiorites of the Yamninsky massif of the Krestovsky complex were obtained, amounting to 371±4 Ma and 364±5 Ma, respectively. These geochronological data are well consistent with the 355–358 Ma ones, therefore suggesting the Late Carboniferous age of quartz-diorite-granodiorite-granite rocks of the Olekminsky complex. However, these dates are not correlated with the existing legends of geological maps covering the area of the Western-Stanovoy structural-formation zone or the Western-Stanovoy terrane, as the intrusive formations of the Olekminsky complex are dated as the Early Paleozoic. In addition, new geochronological data call into question distinguishing of a separate Early Paleozoic Krestovsky granitoid complex.