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The paper presents new isotopic U–Pb data (LA-ICP-MS method) of zircon from the main types of intrusive rocks at the Kuru-Tegerek gold-copper-molybdenum skarn deposit situated in the Chatkal segment of the Middle Tien Shan. This and other gold, copper, tungsten and molybdenum deposits are parts of the extended Late Paleozoic metallogenic belt of Tien Shan. The concordant isotopic U–Pb values obtained for zircon autocrysts from the rocks of sequential intrusive phases span over the interval from approximately 323 to 311 Ma. This interval comprises the crystallization of gabbro-diorite (from 323.5 ± 2.5 Ma to 323.2 ± 6.8 Ma) and tonalite (from 321.4 ± 3.8 Ma to 311 ± 3.8 Ma). The age dates obtained for these zircon autocrysts correspond to the emplacement of these moderate-potassic intrusions in the Late Carboniferous and are almost coincident with the isotopic dates previously known for the high-potassic intrusions of the porphyry Cu–Au–Mo deposits of the Almalyk mineralized cluster (Kurama segment of the Middle Tien Shan), which were also emplaced in the Late Carboniferous (about 330–310 Ma). This corresponds to the subduction tectonic regime occurred in this region in relation to the steep-dipping (in the Kurama segment) or flat (in the Chatkal segment) subduction of a tectonic plate toward the north, under the structures of the Kazakhstan–North Tien Shan continental massif and accreted segments of the Middle Tien Shan. The intrusive rocks studied at the Kuru-Tegerek deposit contain also zircon xenocrysts (including these in the core of complex crystals) with the isotopic U–Pb age of some 1.9–2.1 Ga. These dates are in agreement with the age of metamorphic rocks in the Tarim craton basement and indicate the presence of the ancient continental crust in this segment of the Middle Tien Shan. [ABSTRACT FROM AUTHOR]

Speleothems are unique archives of information on climate, geomagnetism, and environmental conditions of the past, and have been successfully used for paleoclimatic and paleomagnetic studies in the last two decades. The uniqueness of these geological objects lies in the peculiarities of their formation and preservation of a wide range of geochemical, geological and geophysical proxies, and, most importantly, in the ability to obtain time series of the corresponding characteristics in an unprecedentedly accurate resolution using isotope-geochronological dating methods and incremental chronology. This paper presents the first results of dating the Vor speleothem from the Vorontsovskaya Cave (Krasnodar region), which preserved a record of the geomagnetic excursion, obtained by 230Th/U α-spectrometry, 14C dating, and incremental chronology. Such studies have been carried out in Russia for the first time. Despite the limitations of using the methods of isotope geochronology, it was possible to obtain an upper limit on the age of the excursion, which probably occurred no earlier than 5500–6000 years ago. By the method of incremental chronology, the duration of the main phase of the excursion Vor – 871 ± 16 years – was determined with great accuracy. [ABSTRACT FROM AUTHOR]

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X2306017X [ABSTRACT FROM AUTHOR]

The paper presents new petrographic and geochemical data from terrigenous rocks and first U–Pb ages of detrital zircons from sandstones of the Tekturmas zone of Junggar-Balkhash suture zone (central Kazakhstan). Petrographically and chemically the samples under study are greywacke sandstones. We performed U–Pb isotope dating of detrital zircons separated from two sandstones sampled in the northern (TK-17) and southern (TK-27) parts at the periphery of the Tekturmas zone. The distribution of U–Pb ages of zircons from sample TK-27 (northern Tekturmas zone) is unimodal with a major peak at 453 Ma. The distribution of U–Pb ages of detrital zircons from TK-17 sample (southern Tekturmas zone) has a bimodal character peaked at 510 and 450 Ma. Both samples contain a small amount of Precambrian zircons. The most probable sources of ca. 450 Ma zircons are andesitic to volcanic rocks of Tekturmas supra-subduction ophiolites. The ca. 500 Ma zircons are also low-rounded like those younger, but no igneous rocks of that age have been identified in the study area. The youngest U–Pb ages of zircons from both samples are similar (438–437 Ma), suggesting the beginning of sedimentation after the Llandovery. The greywacke composition and the poorly sorted, poorly rounded and immature characteristics of the sandstones under study and the clear major peaks of U–Pb detrital zircon ages at an extremely low amount of old zircons suggest their derivation from short-distant sources dominated by Late Cambrian-Early Ordovician and Middle-Late Ordovician supra-subduction igneous complexes. A very limited amount of oldest zircons could come from Precambrian complexes present at the periphery of both sedimentation basins. [ABSTRACT FROM AUTHOR]

The Uyandina–Yasachnaya volcanoplutonic belt (UYVB) is located in Northeast Asia. As one of the largest volcanic belts in the region, it extends for 900 km from the headwaters of the Kolyma River in the northwesterly direction. The Late Jurassic UYVB overlaps the folds of the Cherskii collision belt. The UYVB rocks are characterized by highly variable facies indicating the heterogeneous nature of the belt. The UYVB has been studied at the cross section of the Indigirka River. This paper reports the first data on U–Pb dating of zircons and the geochemical features of rocks. The concordant U–Pb age of volcanic rocks is 150 ± 2–152 ± 2 Ma (Kimmeridgian–Volgian of the Late Jurassic). It is concluded that the formation conditions of the volcanic rocks change upward through the section, from those typical of mature island arcs to those more typical of active continental margins. [ABSTRACT FROM AUTHOR]

This paper reports on the lithological, micropaleontological, and chronometric data (radiocarbon dating) for one of the areas of the White Sea coast. The sedimentary sequences were studied in the current lake basins, which were separated from the large basin at different times. The basin was situated in the head of the current Onega Bay. On the basis of these data, the bottom sediments were stratified and the Late Pleistocene–Holocene paleogeographic settings were reconstructed for the southeastern part of Onega Bay. [ABSTRACT FROM AUTHOR]

This paper reports on lithium metallogeny in geological time. The geochronological analysis was conducted on the basis of data on 71 lithium deposits distributed globally. These deposits contain almost all Li resources, which are industrially significant and of potential interest in terms of the economy. It was established that these deposits were formed in different geological epochs, from the Late Mesoarchean to the Holocene. The distribution of their resources on the scale of geological time is distinctly discrete. In the Kenoran, Columbian, and Rodinian supercontinent cycles, only pegmatite deposits of lithium were formed. In the Pangean cycle, the main resources are also attributed to pegmatite deposits, but some of them are concentrated in lithium–fluorine rare-metal granites. In the incomplete Amasian cycle, salars of geodynamically active areas play a main role in the resource base; the epithermal stratiform deposits, pegmatites, and lithium-fluorine granites are of much less significance. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of U-Pb isotope-geochronological study on zircons from subalkali gabbros and granodiorites of the Dogaldyn intrusive massif located in the Karalon-Mamakan zone of the Baikal-Muya belt. The ages of 254 ± 2 and 256 ± 1 Ma yielded for rocks of the two main intrusion phases do not differ significantly from each other and correspond to the Late Permian period. The Nd-isotope and geochemical data indicate the relationship between the primary melts of intraplate rocks from the Dogaldyn Massif and various sources, including plume-mantle and ancient crustal ones. The manifestations of Late Permian intraplate magmatic activity in the Baikal-Muya belt could have been induced by the Iberian superplume framed by the Siberian trap province. [ABSTRACT FROM AUTHOR]

This paper reports on the integrated geochronological and geochemical methods used in studying the ore deposits and metalliferous sediments of the Yubileinoye field. This study gives the opportunity to carry out cross dating of hydrothermal deposits, including the 230Th/U dating of sulfides, the 230Th, 14C dating, and foraminiferal analysis of the sediments, and, on this basis, to reconstruct hydrothermal activity over time. It was established that the ores started forming about 100 000-123 000 years ago and were renewed 4-5 times with a frequency of 10-20 ka. As a result, the complex of pyrite-marcasite, chalcopyrite and sphalerite ores and the associated metal-bearing and ore-bearing sediments with consistent geochemical specialization were formed. The integrated geochronological and geochemical studies of the ores and sediments allow us to obtain detailed data on evolution of the hydrothermal ore-formation not only in the certain areas but also for the entire Mid-Atlantic Ridge. [ABSTRACT FROM AUTHOR]

The paper presents results of geochronological and paleomagnetic studies of the volcanogenicsedimentary sequence of Henrietta Island in the East Siberian Sea. Our Ar/Ar investigations confirm existing ideas that the bottom part of the section formed in the Ediacaran (~565 Ma) and that the basalts in the top of the section formed before the middle Cambrian (~520 Ma). Calculated paleomagnetic data confirm that during the rocks formation the territory of present-day Henrietta Island was located close to the 20° latitude, which lets us adjust some information published earlier on the age and natural remanent magnetization of the dolerite dikes of the nearby Jeannette Island. The new data also let us propose that a regional tectonothermal event, probably caused by accretion-related processes, took place at the beginning of the Ordovician. [ABSTRACT FROM AUTHOR]

One of the richest rare metal provinces in Russia occurs within the Altai–Sayan fold area, which spans the territory of the East Tuva Upland and East Sayan. The deposits of rare metals, elements, and earths formed within the province have different ages and originated in different geotectonic settings and metallogenic epochs. They are related to the intrusion of alkaline rocks, which are abundant along the fault system between the Caledonides of the Altai–Sayan fold area and the Precambrian Tuva–Mongolian Superterrane. The area of their occurrence is also recognized as the East Sayan rare metal metallogenic zone (ESMZ), which originated as a result of the mantle plume impact on the SW frame of the Siberian Platform. These geochemical and geochronological studies were conducted at the Ilee fluorite–phenakite occurrence that formed as a result of the intrusion of granitoids of the Ognit Complex into limestones of the Mongosha Formation, which became a geochemical barrier for a F- and Be-rich magmatic fluid. According to Rb‒Sr and Ar‒Ar geochronological studies, the age of subalkali granite and felsic volcanic rocks of the Ilee Sequence is the Middle Devonian (~390 Ma), which is consistent with the age estimations for rocks of the Ognit Complex. Thus, the coeval age of magmatism and ore formation at the Ilee ore occurrence indicates the contribution of Devonian magmatism to the formation of rare metal mineralization of the ESMZ. [ABSTRACT FROM AUTHOR]

This paper reports on geochronological U–Pb studies of baddeleyite from nepheline syenite of the Korgere-Daba alkaline massif, which is the largest massif within the Sangilen Highlands (Tyva). The established age of rocks, 295 ± 1 Ma, indicates that, in the Early Permian, undersaturation by silica magmatism occurred in the region in addition to the alkaline-granite magmatism (Ulug-Tanzek, etc.). This age furthermore points to the need to make corrections in the conceptions of a petrophysical type for the Devonian Sangilen complex, which is traditionally distinguished in this region. Until now, the Korgere-Daba massif has been considered in this regard. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The results of U‒Th‒Pb (LA-ICP-MS) geochronological studies of detrital zircon from metagraywackes of the Kodar Group of the Udokan complex of the Aldan Shield are presented. It is established that the age of terrigenous rocks of the Kodar Group of the Kodar Subzone of the Kodar–Udokan Trough is 2.02−1.91 Ga. The accumulation of rocks of the Kodar Group was separated from the accumulation of rocks of the Chinei and Kemen groups of the Udokan complex and the formation of Cu mineralization of ~1.90–1.87 Ga ago by a deformation and metamorphism stage. Our geochronological data allow us to raise a question on the recognition of the Kodar Group or, at least, its lower part as an individual complex. The rocks of the Kodar Group of the Kodar Subzone were sourced from the Archean (~2.76–2.92 Ga) igneous and metamorphic complexes of the Chara–Olekma Geoblock of the Aldan Shield, as well as unidentified (at the present level of erosion) island arc or active continental margin complexes with an age of ~2.02 Ga in the western–northwestern and southern (in the present-day coordinates) framework of the Chara–Olekma Geoblock. [ABSTRACT FROM AUTHOR]

The age of magmatic rocks of basic composition sampled at the Alpha–Mendeleev Rise in the Arctic Ocean by a research submarine was studied based on the measurement of the U/Pb age of zircons separated from them. Early Cretaceous rocks of the moderately alkaline series, which had been formed at the turn of 112 million years, are most common on the Rise. These rocks contain a large number of ancient xenogenic zircons the age analysis of which shows that the subalkaline melts interacted with the crust at two levels including the horizon of Early Cretaceous sandstones and with rocks of the Late Archean crystalline basement aged 2675.1 ± 11.6 Ma. They also contain a small number of younger zircons aged 83 to 87 Ma, which probably arose during the recrystallization of Early Cretaceous zircons under the influence of Late Cretaceous magmatism. [ABSTRACT FROM AUTHOR]

The U–Pb LA-ICP-MS age is analyzed for detrital zircons from diamondiferous sandstones of the Khuzhir Formation of the Moti Group of a sedimentary cover of the south Siberian Platform. Similar ages are determined for two samples with the most representative maxima at 620, 780, 1860, and 2550 Ma and single data within the ranges of 985–1000, 1400–1500, 1150–1190, 2700–2880, and 3225–3230 Ma. The maximum age of sedimentation is 605 ± 6 Ma, which corresponds to the Ediacaran and is close to a period of carbonatite and alkali-silicate magmatism of the region. The Neoproterozoic ages correspond to the age of rocks of the Tuva–Mongolian Terrane of the Central Asian Orogenic Belt, and the most ancient maxima are typical of the basement rock complexes of the south Siberian Platform. Our result allows the first substantiation of the Precambrian age of diamondiferous sedimentary rocks of the Khuzhir Formation and therefore indicates the presence of Precambrian diamondiferous rocks within the Siberian Platform. [ABSTRACT FROM AUTHOR]

U–Pb (ID-TIMS) geochronological studies of garnet from iron–magnesian metasomatic rocks of the Kurung-Khoonku River ore occurrence (Leglier deposit group, West Aldan megablock) were carried out. The results obtained (1901 ± 5 Ma) are the first age determinations of formation processes of ore-bearing iron–magnesian metasomatic rocks in the Aldan Shield. They are related to the final stages of the Early Proterozoic tectonic–magmatic evolution of the Aldan geoblock. [ABSTRACT FROM AUTHOR]

The U–Pb (ID-TIMS) geochronological studies of garnet from aillikites of the Kandalaksha dike swarm (Kola alkali province) were carried out. The estimated U–Pb age of garnet (374 ± 3 Ma) coincides with the major stage (373–377 Ma) of alkali magmatism in the Kola Province (LIP). Hence, it can be concluded that rocks of the dike complex of Kandalaksha Bay and foidolite-range rocks of alkali–ultrabasic massifs of this province were formed synchronously. [ABSTRACT FROM AUTHOR]

For the first time, the U–Pb and Rb–Sr age of granodiorites of the Birandzhinskii massif, with which the gold mineralization of the Kutyn deposit in Khabarovsk krai is spatially connected, has been determined. Isotope–geochronological data show good convergence: the concordant U–Pb age of zircon is 90.7 ± 1.7 million years (SIMS), and the Rb–Sr age of the rock shaft and minerals is 92.7 ± 0.4 million years. Low εNd(t) values (about –0.8) and high primary 87Sr/86Sr ratios (0.7051–0.7053) relative to the parameters of the depleted mantle suggest that granodiorites were formed with the participation of the continental crust. The formation of the Birandzhinskii massif coincides with the second stage of the development of the Khingan–Okhotsk volcano-plutonic belt. The Rb–Sr age of gold-bearing quartz–carbonate–sericite metasomatites of the Kutyn deposit is 79.3 ± 0.5 million years. The obtained isotope–geochronological data indicate a time gap (about 10–12 million years) between the crystallization of granodiorites and the formation of metasomatites, which suggests the allometasomatic nature of gold mineralization. [ABSTRACT FROM AUTHOR]

The first direct Pb–Pb dating of carbonate rocks of the Kamo Group has been carried out. The Pb–Pb age of carbonates of the lower units (the Madra, Jurubchen, Kuyumba, and Vingold formations) of this sedimentary sequence is 1510 ± 50 Ma, while the age of the upper unit (the Iremeken Formation) is 1490 ± 50 Ma. The ages obtained show that all the carbonate formations of the Kamo Group are Lower Riphean (Early Mesoproterozoic), and their deposition continued for a period of no longer than several tens of millions of years. The new geochronological data allow us to correlate the Riphean deposits of the Baikit Anteclise with the rocks of the Riphean cover of the Anabar Uplift. [ABSTRACT FROM AUTHOR]

The principal possibility of using high-uranium metamict zircon with a high self-irradiation α-dose for U–Pb geochronological studies (ID-TIMS) is demonstrated. The application of the optimal parameters of "chemical abrasion," accompanied by preliminary high-temperature annealing, allowed us to estimate the age of Li–F granites of the Turga massif (Eastern Transbaikalia) (146 ± 4 Ma and 141 ± 1 Ma). [ABSTRACT FROM AUTHOR]

This article presents the 190Pt–4He dating results of native platinum group minerals from a unique platinum-metals placer deposit in the basin of the Kondyor and Uorgalan rivers and dunite fragments from the Kondyor alkaline-ultramafic massif. The results of 190Pt–4He dating of 75 samples determine the age of the minerals and also date the ore-forming processes. It confirms the previously developed model of polycyclic genesis of placer-forming formations of platinum group minerals (PGMs) and, thus, sheds light on the duration of the formation of the Kondyor alkaline-ultramafic massif. The following 190Pt–4He age stages are distinguished: (a) 143 ± 7 Ma, the formation time of the massif itself and early formation stages of PGMs of magmatogenic platinum (Pt) and the magmatogenic–fluid–metasomatic Pt and Os–Pt (Pt > Os) types, as well as PGMs of fluid-metamorphogenic iridium–platinum (Pt > Ir) type; (b) 128 ± 6 Ma, the early formation stages of the magmatogenic–fluid–metasomatic Pd–Pt (Pt > Pd) type and the late stages of the Pt, Pt > Os, and Pt > Ir types; (c) 115 ± 6 Ma, the late formation stages of the Pt > Pd type. The good agreement of these dates with the geological and mineralogical data allows us to conclude that the formation of placer-forming PGMs and their formations in the Kondyor alkaline-ultramafic massif was a polycyclic process for about 30 Ma. [ABSTRACT FROM AUTHOR]

Based on the results of U–Th–Pb (SIMS) dating, an Early Neoproterozoic (924 ± 4 Ma) age was obtained for granite–gneiss of the Sarychabyn Complex, which is one of the oldest complexes in the Junggar Alataw Range. This value constrains the minimum age of the metasedimentary rocks of the Sarychabyn Group hosting granite–gneiss as well. The most likely age of metasediments is Late Mesoproterozoic–Early Neoproterozoic, which is consistent with the age of lithologically similar complexes in the adjacent regions of Kazakhstan and China. The age of the gneiss of the Sarychabyn Complex coincides with the ages of anorogenic granitoids and felsic volcanic rocks from the Aktau-Mointy massif of Central Kazakhstan and the ages of granitoids in the Wenquan Complex in China. An episode of granitoid magmatism at ~920 Ma, widespread in the Aktau-Junggar microcontinent, is a characteristic feature that distinguishes it from other Precambrian crustal blocks of Kazakhstan and the Northern Tianshan. [ABSTRACT FROM AUTHOR]

This work presents results of isotope studies of primary igneous and sedimentary rocks of Mawson and Menzies series from the southern Prince Charles Mountains, East Antarctica. The data obtained show that the crystallization of the protolith of Mawson orthogneisses occurred at 3164.2 ± 9.2--3163.2 ± 7.8 Ma ago. The Mawson orthogneisses were the basement for accumulation of the deposits of the Menzies series. The maximum time of the deposition is estimated to be in a range of 3.0--3.1 Ga. The protolith of Menzies sedimentary deposits contains an admixture of the Paleoarchean material. [ABSTRACT FROM AUTHOR]

The results of U–Th–Pb geochronological study indicate that the youngest peaks on the relative probability curves of the age obtained for the Un'ya-Bom terrane correspond to ages of 207 and 212 Ma. These values were obtained for zircons from the meta-aleurolite samples from the Kurnal and Amkan formations, respectively. Similar age estimates for the youngest peaks were also obtained in the case of detrital zircons from the metasedimentary rocks of the Tukuringra terrane in the eastern part of the Mongol–Okhotsk fold belt, which indicates that, within the belt, Lower Mesozoic flyshoid complexes are much more widespread than was assumed. Based on the geochronological and Sm–Nd isotopic data obtained, it was shown that the material was carried to the sedimentation basin mainly from the continental massifs of the Amur superterrane. [ABSTRACT FROM AUTHOR]

The results of U–Pb dating of detrital zircons extracted from rocks of the Ai Formation are presented. A provenance-signal of a local source with an age of about 2.07 Ga has been documented, and the effect of the Ordovician magmatic episode on the sedimentary sequence has been revealed. [ABSTRACT FROM AUTHOR]

Based on analysis of new data on the geodynamical nature, ages of formation, and magmatic sources of contrasting rocks from the tectonic mélange of the Yenisei shear zone, the chronological sequence related to early stages in the evolution of the Paleoasian Ocean was established. The data obtained specify the legend and stratigraphic scheme of the Yenisei Group and peculiarities in the evolution of the Sayany-Yenisei accretionary belt at the final stage of its Neoproterozoic history. [ABSTRACT FROM AUTHOR]

This report presents the results of U-Pb geochronological LA-ICP-MS studies of detrital zircons from metasedimentary rocks of the western part of the Tukuringra terrane. The obtained data show that the Algainskaya, Garmakanskaya, and Teploklyuchevskaya series in the western part of the Tukuringra terrane are not of Middle Paleozoic but of Early Mesozoic age. It is shown that the main sources of clastic matter for these formations were Late Precambrian, Paleozoic, and Late Triassic-Early Jurassic complexes of continental massifs of the Amur superterrane. [ABSTRACT FROM AUTHOR]

New LA-ICP-MS data on the U-Pb isotope age, Hf isotope characteristics, and concentrations of trace elements in zircons from volcanic tuff of the Upper Vendian Sylvitsa Group on the western slope of the Middle Urals are reported. [ABSTRACT FROM AUTHOR]

The spatial and temporal characteristics of magmatism caused by the Barents-Amerasian Jurassic-Cretaceous plume in conjunction with the geodynamics of destructive transformations of the lithosphere are presented here. The localities of manifestation of magmatism were concentrated mainly out of general contour of the areal occupied by the Siberian superplume, and they demonstrated certain gravitation to the Caledonide-Ellesmeride belts. This suggests an inherited position of both the J-K plume and the initial detachment zone produced by it: this led to formation of the Canadian Basin. The stages in the evolution and character of polycyclic multiphase plume magmatism are substantiated by the geochronology of magmatic provinces in the Arctic region during formation of the Amerasian Basin. [ABSTRACT FROM AUTHOR]

The results of Sm-Nb isotopic-geochemical studies of metasedimentary and metavolcanic rocks of the Dzheltulak Group of the central part of the Dzheltulak suture, as well as geochronological U-Th-Pb (LA ICP MS) studies of detrital zircons from metasedimentary rocks, which are considered as Paleoproterozoic in current stratigraphic schemes, are presented. The age of the youngest zircons is 170-190 Ma, whereas the age of the last stage of regional metamorphism is 140-150 Ma. Thus, the Dzheltulak Group hosts metasedimentary rocks, the age of the protolith of which ranges from 140-150 to 170-190 Ma. The detrital zircons derived from intrusive and metamorphic rocks of the Selenga-Stanovoi and Dzhugdzhur-Stanovoi superterranes. [ABSTRACT FROM AUTHOR]

The products of the activity of the Late Quaternary Kazbek neovolcanic center in the Greater Caucasus are studied by isotopic-geochronological methods. It is found that the youngest magmatism evolved during the last 400-450 k.y. over four discrete phases: 395-435, 200-250, 90-120, and less than 50 ka. The petrological-geochemical and published isotopic data point to the mixed mantle-crustal origin of the Kazbek lavas with the leading role of crystallization differentiation of deep magmas and assimilation of the crustal material. We recorded two episodes (∼100 and less than 50 ka) of replenishment of the subsurface magmatic chamber under the Kazbek center by the main mantle melt and its mixing with the relict dacite magma that led to the formation of highly mobile hybrid andesite lavas and served as a trigger of the renewal of volcanic activity. Reactivation of the mantle source of the Kazbek center at the end of the Neopleistocene and the Holocene age of the last eruptions indicate the potential danger of this region because of the renewal of the volcanic activity. The medium Devdoraki copper deposit is located in the vicinity of the Kazbek volcano. It represents a unique polychronous, currently evolved ore-magmatic system that originated in the Jurassic. [ABSTRACT FROM AUTHOR]

The article focuses on the determination of terminal stage of collisional magmatism in the Western Magnitogorsk Zone of the South Urals, Russia using Samarium-neodymium dating method. Topics discussed include factors associated with age estimation such as intersection of intrusive bodies and dikes, mineralogical composition of hornblende dolerites and porphyrites, and presence of large-ion lithophile elements such as cesium and rubidium.