The results of U–Th–Pb (LA-ICP-MS) geochronological studies of detrital zircon from metasedimentary rocks (high-alumina, garnet-biotite, biotite gneisses and hypersthene-bearing quartzite-gneisses) of the Kurumkan Group of the West-Aldan megablock of the Aldan Shield are presented. It is established that igneous complexes of Paleoproterozoic (2.07, 2.31 and 2.45 Ga), Neoarchean (2.56 and 2.67 Ga), as well as Meso- and Paleoarchean (about 2.80−3.26 Ga) age were the sources of the metaterrigenous rocks in the Kurumkan Group, and the age of superimposed metamorphism is approximately 1.94 Ga. Significant differences in the age of the metasedimentary rocks in the Kurumkan Group (ca. 2.1−2.0 Ga) and the associated metavolcanics (ca. 2.4 Ga) indicate that these rocks belong to different stratigraphic units. The age of the metasedimentary rocks in the Kurumkan Group is close to that of the island-arc rocks of the Fedorov Group. The most likely geodynamic setting for the formation of the protoliths of the metasedimentary rocks in the Kurumkan Group is a back-arc basin, synchronous with the formation of the Fedorov island arc.

Massifs of alkaline granitoids and nepheline syenite are widespread in Eastern Tuva and are frequently associated with rare-metal deposits and occurrences, which formed mainly during the Late Carboniferous and Permian. The Naryn massif comprises nepheline syenite of the main phase, rocks of the contact zone, and a complex of three types of foidite microsyenite dikes. Zircon U-Pb geochronology yields ages of (SIMS - 315 +/- 3 Ma) for the main phase and (CA-ID-TIMS - 318 +/- 1 Ma) for the microsyenite-1 dikes, indicating that the massif was emplaced during the Middle Carboniferous. The mineralogical, geochemical, and Nd isotopic characteristics of the massif rocks suggest that their diversity results from the differentiation of a single parental magma, a process that occurred at different hypsometric levels. Crystallization of biotite-pyroxene-amphibole nepheline syenite of the main phase and feldspar liebnerite syenite of the marginal zone occurred at the upper level. Dikes of apo-amphibole nepheline microsyenite-1, pyroxene-biotite microsyenite-2, and biotite nepheline microsyenite-3 were emplaced sequentially from a deeper chamber containing the differentiating melt. The evolution of the melts at both levels was driven by the fractionation of mafic minerals (amphibole), apatite, and feldspar. As melt alkalinity increased, rare elements such as Zr, Nb, Ta, and REE accumulated, eventually forming their own mineral phases during the late stages of crystallization. These findings indicate that the widespread foidite-series rocks of Eastern Tuva may be potentially ore-bearing, and the Middle Carboniferous should be considered as a distinct phase of alkaline magmatism within the East Sayan rare-metal metallogenic zone. The Nd isotopic composition of the Naryn massif rocks (epsilon Nd(T) = 6.3-7.1) precludes significant involvement of continental crust in their source. Therefore, sublithospheric alkaline basaltoid magmas are interpreted to be the parental magmas for all rocks of the Naryn massif.

Geochemical and geochronological (U–Pb method on zircon, ID-TIMS) studies of igneous rocks of the Olekma–Stanovoy dike complex in the eastern segment of the Stanovoy volcano-plutonic belt of the Central Asian orogenic belt have been carried out. The age of intrusion of rhyolite dikes of this complex has been established as 110 ± 1 Ma. This age corresponds to the completion of the Stanovoy volcano-plutonic belt’s formation in its eastern segment within the Dzhugdzhuro–Stanovoy superterrain. This terminal magmatic impulse in the Stanovoy belt (110 Ma) is represented exclusively by felsic rocks, including rhyolite dikes of the Olekma–Stanovoy complex, rhyolites of the Ugan volcanic field, and granites of the Irakan complex. All of them are classified as high-silica and high-alumina rocks of increased alkalinity with a predominance of potassium, and belong to the transitional geochemical type between A- and S-type granites. Unlike earlier granitoids from the batholithic stage of the Stanovoy volcano-plutonic belt’s formation, they are enriched in rare elements, are significantly more differentiated, and lose the geochemical features of adakite-type magmatism typical of earlier igneous rocks in the eastern segment of this belt. These rocks were probably formed under conditions of lithospheric tension, which is fully consistent with the concept of the Stanovoy volcano-plutonic belt’s formation during the post-collisional stage of geological evolution in the northeastern sector of the Central Asian orogenic belt.

The results of U–Pb (ID-TIMS) geochronological studies of zircon from biotite–hypersthene plagiogneiss (metadacite) of the Kurumkan Formation, Aldan Shield, are presented. The obtained crystallization age of the biotite–hypersthene plagiogneiss protolith is 2395 ± 6 Ma. Metasedimentary rocks of the Kurumkan Formation, some of which are characterized by Nd model ages tNd(DM) = 2.3–2.2 Ga, are clearly younger than metavolcanic rocks. This indicates that the formation includes rocks of different ages, whose origin is associated with distinct stages of the Early Proterozoic geological evolution of the Aldan Shield.

This paper presents the results of U–Pb (CA-ID-TIMS) geochronological studies obtained for tapiolite from pegmatite vein at the Belskoe ore field which is a part of the East Sayan rare-metal pegmatite belt. A range of laboratory experiments was conducted, and pre-annealing and acid treatment of tapiolite were applied for the first time. This method is similar to “chemical abrasion” of metamict zircon. As a result of the U–Pb geochronological studies of tapiolite at the Belskoe ore field, the age estimate of 1799 ± 2 Ma was obtained for the first time for pegmatites of the Urik–Iya graben. These data are consistent with the age estimates obtained earlier at other pegmatite fields in the East Sayan pegmatite belt and confirm that the pegmatite formation age is 1.80–1.82 Ga in the region under consideration.

The results of geochronological studies of rodingites from the Zolotaya Gora gold deposit (Southern Urals, Russia) are presented. The age of the hydrothermal process, which led to the formation of copper gold clusters in altered serpentinites, was determined by using the Fe‒Ti‒Ca garnet for the first time. The U‒Pb dates obtained (299 ± 1 Ma) corresponds to the initial stage of the collision development of the southern segment of the Uralian Fold Belt. Based on the results of studying the internal structure of the garnet, the stages of its formation are established. The second stage of garnet formation in rodingites corresponds to the stage of formation of the gold ore mineralization of the deposit.

Research subject . Zircon of sandstones of the Basu Formation, Asha Series, Vendian, in the reference section along the Kukrauk stream (Southern Urals). Aim. To determine the age of rocks in the provenance based on U-Th-Pb (LA-ICP-MS) dating of zircon clastics. Materials and methods . In terms of color, detrital zircon grains were divided into three groups. Pale pink grains predominate (about 50%), and pink and colorless grains are present in equal proportions (about 20–30%). Zircon is mainly represented by rounded grains and single grains of a prismatic shape. According to the cathodoluminescence data, most grains retain traces of zonation. Results. The U-Th-Pb concordant ages dates of 166 detrital zircon grains are predominantly in the time intervals of 996–1029, 1079–1110, 1152–1191, 1200–1234, 1250–1324, 1331–1370, 1416–1438, 1447–1557, 1573–1666, 1756–1806, 1824–1874, 1889–1979, 1987–2015, 2022–2074, and 2661–2729 Ma. Individual grains have concordant ages of 579, 776, 2120, 2142, 2148, 2190, 2763, 2874, 2804, 2816, 2889, 2957, 3014, and 3203 Ma. Conclusions . The group of pink grains is dominated by a population of zircon of the Early Karelian and Archaean age, in colorless grains – Early Riphean, and in pale pink grains – Early and Middle Riphean. Among the grains of detrital zircon from the sandstones of the Basu Formation, there are zircons from local Ural sources (776, 1350–1800, 2000–3200 Ma). For clastic zircon with ages of 996–1320 Ma, the sources of demolition among the local feeding provinces have not been identified; however, they are known within the Sveko-Norwegian area in the north-west of the East-European Platform. This allows us to consider the igneous rocks of the Grenville (950–1220 million years) Sveko-Norwegian orogen as sources of zircon clusters over this time interval. The source of zircons with a dating of 579 Ma, closeto the age (573–577 Ma) of zircons from tuff layers in the Basu Formation itself, could be ash material from the explosive activity of volcanoes

The results of U–Pb (ID-TIMS, single grain) of monazite from aluminous gneisses (Chupa belt, Belomorian province) define the age of two metamorphic events associated with the formation of the Belomorian and Lapland–Kola orogens (the age of monazite is 2736 ± 30 and 1857 ± 4 Ma, respectively). These monazite ages are consistent with results of local U–Th–Pb (LA-ICP-MS) geochronological studies of zircon with Paleoproterozoic age of rims and 2809 age of cores 2809 ± 17 Ma.

The paper presents the results of U–Pb (CA-ID-TIMS) geochronological studies of columbite-tantalite and zircon from the pegmatite vein of the Aleksandrovskoye ore field, which is part of the East Sayan rare-metal pegmatite belt. As a result of U–Pb geochronological studies of columbite, age estimates of 1825 ± 3 Ma were obtained for the first time for the quartz core of the pegmatite vein and 1817 ± 5 Ma for the zone of intense alteration of amphibolites within its exocontact. The age estimate of 1810 ± 5 Ma was obtained for metamict zircon from the boundary zone of the quartz core. The studies suggest that the age of rare-metal pegmatites of the Aleksandrovskoye ore field in the East Sayan pegmatite belt differs significantly from that of the spatially conjugated granitoids of the Sayan complex (1.86–1.90 Ga).

New U–Pb (CA-ID-TIMS) zircon age data were obtained for metadacite from the Mezhezero Formation of the Megriyarvy structure of the Gimoly–Sukkozero belt of the Central Karelian domain (Karelian Province, Fennoscandian Shield). Metadacites are fine-grained rocks with porphyritic plagioclase phenocrysts in the epidote-muscovite-biotite-quartz-plagioclase matrix. In terms of chemical composition, dacites are characterized by the enrichment in Ba (900–1300 ppm), Sr (average of 650 ppm), LREE (average (La/Yb)n = 20; La = 38 ppm), as well as by well-defined negative Nb and Ti anomalies on the spider diagram. The concordant U–Pb age of zircon from metadacites is 2735 ± 6 Ma (MSWD = 0.061). The whole-rock εNd(t) values are +0.5 and +0.8 and the tNd(DM) values are 2.83–2.85 Ga. Neoarchean metaandesites and metadacites, similar in composition, structural features, age, and Nd isotope composition, are also present in other greenstone belts of both the Central Karelian domain and beyond. Metadacites are similar in age and geochemistry to the granitoid varieties of the sanukitoid series of the Karelian Province but differ from primitive sanukitoids in lower contents of MgO, Cr, Ni, alkalis, REE (especially LREE), Ba, and Sr. They correspond to sanukitoids of the normally alkaline group, i.e., rocks of an intermediate composition between the rocks of the tonalite-trondhjemite-granodiorite association and subalkaline sanukitoids, and, possibly, are their effusive analogs. In the Gimoly–Sukkozero belt, the polymictic conglomerates of the Sukkozero Formation (plagioclase porphyry pebbles, matrix, interbeds of biotite-quartz-plagioclase schists) are similar to metadacites of the Mezhezero Formation in the composition and the U–Pb zircon age of about 2.76 Ga. This may indicate subsynchronous volcanism and sedimentation in this structure in the early Neoarchean.

The oldest granitoids of the Kan–Chingiz Complex with quartz diorites, granodiorites, plagiogranites, and granites are dated for the first time in the Chingiz–Tarbagatai region of eastern Kazakhstan. The U‒Pb (ID-TIMS and SIMS) age of granites and plagiogranites is 509 ± 2 and 512 ± 3 Ma, which corresponds approximately to the Early–Middle Cambrian boundary. These data indicate the Early Cambrian age of volcanosedimentary sequences host granitoids. The peculiarities of the composition of granitoids of the Kan–Chingiz Complex point to their formation within an ensimatic island arc.

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

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 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.

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.

The Late Ordovician and Silurian ages, previously considered as the Precambrian, were established for the first time for plutonic and volcanic complexes of the Karakamys block of Southwestern Kazakhstan. U–Pb (SIMS, and ID-TIMS) geochronological study of gneiss–granites and felsic volcanic rocks was carried out, and age estimates of 443 ± 5 Ma and 436 ± 2 Ma, consequently, were obtained. These data allow us to refer gneiss–granites to the very end of the Ordovician and the beginning of the Silurian, and felsic volcanic rocks and tuffs, to the Llandovery series of the Silurian. Special features of the composition of granitoids and felsic volcanic rocks indicate their formation in supra-subduction settings.

New and previously obtained paleontological data from the Vendian reference sections of the central and southwestern areas of the East European Platform are analyzed. Various associations of organic-walled microfossils and macroscopic fossil organisms of Redkino and Kotlin age are widespread in the Upper Vendian terrigenous deposits of northwestern Russia, northern Belarus, and western Ukraine. It is assumed that the Redkino and Kotlin intervals correspond to two major stages of transformation in the communities of fossil organisms. Finds of new fossils, including those representing animals, in the Upper Vendian deposits of the Kotlin Regional Stage suggest a more complex composition of the Kotlin biota than previously thought.