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The first U-Pb isotope-geochronological data were obtained on the age of early collisional granitoids of the Matut massif (Western Sangilen, SE Tuva). The rocks that have been studied are assigned to magnesian, calc-alkaline, high-potassium, and low-peraluminious varieties. LA-ICP-MS analysis on two zircon samples showed that the Matut granite massif formation age corresponds to 522 Ma (U/Pb, LA-ICP-MS, zircons, 520±3 Ma (sample KT-1070) and 524±3 Ma (sample KT-1324)). Thus, the Matut massif granitoids are among the most ancient in Western Sangilen and were formed at the early collisional stage of the structural evolution of the region. Based on the data obtained, an assessment was made of the duration of collisional orogeny on the northwestern margin of the Tuva-Mongolian massif. The initiation to collapse period of the orogen is at least 80 million years.

This paper presents the results of isotope-geochronological and petrological studies of gabbroic and combined diorite-granite dikes located in the eastern part of the Kaakhem magmatic area. Both groups of dikes cut through diorite-tonalite-plagiogranite associations of different ages (489±5 and 476±4 Ma). Zircons from granitoid of mingling dikes have an age of 477±3 Ma (LA-ICP-MS). The age of the gabbroic dikes was determined by LA-ICP-MS (zircon) and Ar-Ar (amphibole) methods and is 454±10 and 450±6.3 Ma, respectively. Similar contents of major and trace elements in basic and intermediate rocks of dikes indicate their formation from a single source with subduction characteristics. The salic rocks of the combined dikes vary in composition and are close to the heterogeneous diorite-tonalite-plagiogranite-granite associations of the host rocks. The formation of dike complexes occurred at the collisional stage of development of the Kaakhem magmatic area and is associated with the development of local extension zones.

The Srednyaya Zima alkaline-ultramafic carbonatite complex is located in the Eastern Sayan and is a part of the area of manifestation of Neoproterozoic rare-metal alkaline-carbonatite magmatism along the southern and southeastern margins of the Siberian craton. Mineralogical studies of calciocarbonatites of the Srednyaya Zima complex have shown the presence of primary magmatic mineral phases of calcite, biotite (annite-phlogopite), ilmenite, and fluorapatite. Pyrochlore, zircon, burbankite, magnetite, rutile, titanite, strontianite, and barite were identified of the accessory minerals. The chemical composition of the magmatic minerals of the Srednyaya Zima carbonatites is similar to the mineral composition of the closely aged carbonatite complexes Belaya Zima and Arbarastakh. The rare-element and structural analysis of zircon from carbonatites showed the presence of two zones – a magmatic core and areas of recrystallization. U-Pb dating of igneous zircon showed the age interval of its crystallization – 637±4 Ma, which coincides with the geochronology of the formation of alkali-ultramafic rare-metal complexes along the southern margin of the Siberian craton. The formation of Neoproterozoic alkaline-carbonatite complexes is associated with tectonic events of the breakup of the Rodinia supercontinent.

Geochronological studies have been made on the main types of rocks from the Burpala alkaline massif and two gabbro and gabbro-diorite dikes located nearby. U-Pb LA-SF-ICP-MS zircon geochronology for the Burpala massif yielded a date of 294±2 Ma for gabbro crystallization, 607±4 Ma for diorite crystallization, 298±2 and 296±2 Ma for melanocratic alkaline and nepheline syenite crustallization, 291±2 and 293±3 for quartz and quartz-containing syenite crystallization, and 293±3 Ma for alkaline granite crystallization. The stage of formation of the massif rocks (298–291 Ma) coincides with the formation period of alkaline rocks from the Synnyr pluton and some alkaline complexes of the Vitim segment of Transbaikalia and confirms a widespread occurrence of post-collisional alkaline magmatism in Western Transbaikalia.

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 results of U-Pb LA-ICP-MS dating of 150 detrital zircon grains from the Precambrian (Riphean?) sandstones of the Kildin group on the coast of the Ivanovka Bay (northeastern Kola Peninsula) are presented. A group of three youngest grains yielded constraint on the sandstone maximum depositional age of 1179±45 Ma. Detrital zircon age distribution is dominated by three maximums of 1.9, 2.4 and 2.7 Ga. The authors consider two complementary scenarios of interpretation of the data obtained. The first scenario involves the contribution of distant provenance out of granitoids in the Lapland-Kola orogen (~1.9 Ga) and adjacent areas of the Kola-Karelia region (~2.7 Ga), Imandra-Varzuga structure (~2.4 Ga), and Sveconorwegian belt (~1.2 Ga); the off-Baltic (Greenland?) sources of the detrital zircon also cannot be excluded. According to the second scenario, the Ivanovsky graben received zircons also from the proximal sources – sialic complexes formed upon melting of granite-gneiss substratum of the upper crust of the Murmansk craton during largescale episodic mafic magmatism 1.86, 2.50 and 2.68 Ga. The Raman spectroscopy showed that about 25 % of the analyzed detrital zircon grains experienced a 1.4-Ga-old thermal effect which did not lead to Pb losses but partially restored the crystalline structure of zircon. This result can be used as an additional constraint in the detailed provenance analysis of the northeastern East European Platform sedimentary basins and is indicative of 1.4-Ga-old large-scale magmatic events related to the breakup of the supercontinent Nuna.

Based on the isotope-geochronological (zircons, U-Pb method), petrogeochemical, and structural and petrologic data, the following paper provides a detailed description of the characteristics of the Late Paleozoic basic and granitoid magmatism in the eastern part of the Kaakhem magmatic area (Eastern Tuva). During the formation of the Shivey alkaline-granitoid and Chadal gabbroid massifs in the period of 292–283 Ma, there were revealed two stages of contrasting magmatism. The early stage is characterized by the formation of plutonic mingling structures and intermediate rocks. Deformation structures, widespread in the early-mingling rocks, are superimposed and formed in extensional regime. At a later stage, there occurred a sequential intrusion of salic and mafic magmas into the zones of local extension in the early-mingling host rocks. A similar petrogeochemical composition of basic rocks of the early and late mingling indicates that they all formed from enriched magma. Granosyenites and granites are derived from melting of tonalities and metasedimentary rocks with a significant contribution of the mantle component. The simultaneous formation of the Chadal gabbroid and Shivei granitoid massifs took place at the intraplate stage of the development of geological structures of Eastern Tuva in the Late Paleozoic.

We present new age constraints for igneous rocks and ore-metasomatic formations of the gold deposits in the Akzhal-Boko-Ashalin ore zone. In terms of their ore formation, these deposits correspond mainly to the orogenic type, which generally reflects specific metallogeny of the West Kalba gold-bearing belt in East Kazakhstan. Gold-quartz veins and mineralized zones of the gold-sulphide formation are confined to fractures feathering regional NW-striking and sublatitudinal faults. Their common features include the following: gold-bearing veinlet-disseminated pyrite-arsenopyrite ores that are localized in carbonaceous-sandy-schist and turbidite strata of different ages; structural-tectonic control of mineralization, numerous dikes of medium-basic compositions in ore-control zones; and the presence of post-orogenic heterochronous granite-granodiorite rocks, although their relation to gold-ore mineralization is not obvious. Igneous rocks of the study area have similar ages in a narrow range from 309.1±4.1 to 298.7±3.2 Ma, which is generally consistent with the previously determined age of granitoid massifs of gold-ore fields in East Kazakhstan. A younger age (292.9±1.3 to 296.7±1.6 Ma) is estimated for felsic rocks of the dyke complex. For the ore mineralization, the 40Ar/39Ar dating of sericite from near-ore metasomatites yields two age intervals, 300.4±3.4 Ma and 279.8±4.3 Ma. A gap between of the ages of the ore mineralization and the igneous rocks is almost 20 Ma, which may indicate that the processes of ore formation in the ore field continued in an impulse-like pattern for at least 20 Ma. Nevertheless, this confirms a relationship between the hydrothermal activity in the study area and the formation and evolution of silicic igneous rocks of the given age interval, which belong to the Kunush complex, according to previous studies. This interpretation is supported by reconstructed tectonic paleostress fields, showing that directions of the main normal stress axes changed during the ore mineralization stage, which is why the ore bodies significantly differ in their orientations. The above-mentioned data are the first age constraints for the study area. Additional age determinations are needed to further improve understanding of the chronology of ore-forming processes. Actually, all the features characterizing the gold mineralization of the Akzhal, Ashalin and Dauba ore fields, including the data on lithology, stratigraphy, structural tectonics, magmatism, isotope geochronology, mineralogy and geochemistry, can be used as criteria when searching for similar ore fields in East Kazakhstan.