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.

The results of U–Pb (ID-TIMS) geochronological studies of vesuvianite from ore-bearing metasomatites of Khopunvaara ore occurrence (Pitkyaranta ore district, Northern Ladoga region) are presented. The resulting age estimate (1550 ± 6 Ma) coincides within the error with the age of formation of ore-bearing skarns that are genetically related to the rapakivi granites of the Salmi batholith. This indicates the possibility of using vesuvianite as a U–Pb mineral-geochronometer, including for ore-bearing contact-reaction rocks.

U–Th–Pb (LA-ICP-MS) geochronological studies of detrital zircon from the Quaternary deposits of the western part of the Ufaley block (Middle Urals) were performed. The studied area was a tectonic fragment composed of an amphibolite–gneiss complex containing bodies of Precambrian clinopyroxenites. The pronounced age maximum corresponds to the age interval of 2100–2000 Ma, and several small peaks correspond to the interval of 3200–2500 Ma. All this gives us a good reason to believe that Early Precambrian rocks, which have not been identified before, are present within the Ufaley block.

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.

Mineralogical and U–Pb (ID-TIMS) geochronological studies of garnets from three types of scarn associations of the Khovu-Aksy Ag–Bi–Cu–Ni–Co deposit (Republic of Tuva) are carried out. The U–Pb garnet age estimate (404 ± 2 Ma) is close to the Early Devonian stage of basite and alkaline-basite magmatism identified within the Tuva trough of the Altai-Sayan folded area. The age of the scarn formation and the associated early stage of mineralization of the Khovu-Aksy Ag–Bi–Cu–Ni–Co deposit has been established for the first time.

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 article presents the results of studying and substantiating the age of Late Precambrian volcanosedimentary and plutonic complexes of the northern part of the Ulutau terrane (Northern Ulutau) in western Central Kazakhstan. The obtained age estimates (SHRIMP II, ID-TIMS, LA-ICP-MS) indicate the formation of acidic effusives and granitoids in the second half of the Tonian of the Neoproterozoic 835‒747 Ma ago. Geochronological and isotope-geochemical data allow us to consider these formations as analogues of stratified and plutonic complexes of Southern Ulutau, which formed in various parts of the lateral series of structures of the Late Precambrian active continental margin.

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 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 issue of the age of rare-metal granites of the Zashikhinskoye field is discussed. To obtain U–Pb (ID TIMS) geochronological data, a modified “chemical abrasion” technique with preliminary high-temperature annealing was used for metamictic zircon. Estimates of the age of alkaline leucogranites and albitites coincide and correspond to the age of formation of rare-metal granites of the Zashikhinskoye field 267 ± 1 Ma. Within East Sayan, igneous rocks with close ages are not yet known. The closest area of magmatic activity of this time was the large zonal Khangai magmatic range, which arose under the influence of the mantle plume and is characterized by widespread development in its peripheral part of alkaline and bimodal associations, including rare-metal magmatic ones. The Zashikhinskoye field is more than 350 km from the edge of its range. Nevertheless, on the basis of geochronological and geochemical data, it was assumed that this field was associated with the activity of the Khangai plume.

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.

This work focuses on petrological-and-geochemical features, as well as age of dolerites widespread within the basins of the Mara, Kamenka and Uvat rivers. The isotope geochronological data acquired for baddeleyite allowed referring origination of these rocks to the time interval 1600–1620 Ma, interpreted as the time of their emplacement. It was ascertained, that the age of dolerites represents particular geological event proceeding independently of formation of Neoproterozoic Nersinsk gabbro-dolerite complex. The Sm-Nd isotope signature indicates that parent melt generated from the metasomatic lithosphere mantle.