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The Komsomolsk tin-ore district is located along the Miao-Chan Ridge in the Middle Amur River area (Khabarovsk krai) within the Badzhal accretionary terrane of the Sikhote-Alin orogenic belt. This work presents new results of U–Pb zircon dating of tonalite from the Miao-Chan complex of the Silinka granite pluton (99.7 ± 1.1 Ma) and rhyolites of the lower part of the Kholdami Formation (98.4 ± 1.0 and 98.7 ± 1.2 Ma) from the northeastern part of the Komsomolsk district. The geochemical characteristics of the rocks studied show that granitoids of the Miao-Chan complex are I-type rocks and that synchronous rhyolites of the Kholdami Formation are highly aluminous and correspond to S-type rocks. New data on the composition and early Cenomanian age of the rocks make it possible to consider the ore-magmatic system of the Komsomolsk ore district as part of the previously identified Albian–Cenomanian igneous province of Pacific Asia. [ABSTRACT FROM AUTHOR]

The results of U‒Pb (ID-TIMS) geochronological studies of garnet from iron-bearing skarns of the Shalym deposit (Kondoma ore field, Gornaya Shoriya) are presented. Our data are the first direct estimation of the age of the formation of the iron deposit of the Kondoma ore field (499 ± 1 Ma). The formation of this deposit is related to the Middle to Late Cambrian subalkaline magmatism, which hasn't previously been recognized within the Gornaya Shoriya fold areas (the western part of the Altai–Sayan fold area). [ABSTRACT FROM AUTHOR]

A rostrum fragment of a representative of the Toarcian–Early Aalenian (the latest Early Jurassic–the earliest Middle Jurassic) belemnites Arcobelus cf. krimholzi (Sachs, 1970) was found for the first time in kimberlites of the Obnazhennaya pipe of the Kuoika kimberlite field (northeastern Siberian Platform, Olenek Uplift). It was shown that the belemnite records previously known here and dated to the Late Jurassic or Early Cretaceous may be of Bajocian–Bathonian (Middle Jurassic) age. The stage of kimberlite magmatism of 177 ± 1.5 Ma, recently established in the northeastern part of the Siberian craton according to U–Pb geochronological data, falls on the time of the existence of belemnites of the genus Arcobelus. The estimated Late Bajocian–Early Bathonian age of the representative of the genus Pachyteuthis, previously found in kimberlites of the Obnazhennaya pipe, is consistent with the 40Ar/39Ar age (167 Ma), as well as with the age based on some paleomagnetic data (168 ± 11 Ma) reported for the pipe. Taking into consideration the new data on belemnites, the internal part of the shelf should be extended to the territory of the Kuoika kimberlite field in the paleogeographic schemes of the northeastern part of the Siberian Platform during the Toarcian–Early Bathonian. [ABSTRACT FROM AUTHOR]

In the present contribution, we aim to better constrain the age of the oldest arc-related volcanic units in the North Tianshan of Kyrgyzstan (NTS) in order to improve our understanding of the early evolution of subduction systems in the western part of the Central Asian Orogenic Belt. We conducted zircon U–Pb dating (LA-ICP-MS) on andesitic tuffs from the Sultansary and Tashtambektor formations, which were previously believed to be of early Cambrian and middle Cambrian to early Ordovician age, respectively. The results reveal ages of 491 ± 3 and 487 ± 3 Ma for these formations, indicating that both units are of Late Cambrian age. We conclude that these volcanic rocks belong to a major magmatic arc that evolved on a heterogeneous basement in the NTS during the Late Cambrian and Early Ordovician. [ABSTRACT FROM AUTHOR]

The paper presents new isotopic U–Pb zircon data (LA-ICP-MS method) on the intrusive rocks from the Chinorsai massif, which is spatially and probably genetically related to the large Jilau tungsten-gold deposit. This deposit, together with the other large Au deposits (Muruntau, Zarmitan, Kumtor, etc.) is part of the largest Au (Au–W) metallogenic belt of Tien Shan. The deposit is represented by small zones of scheelitebearing skarn and later (overprinting) large stockwork of veins and veinlets with scheelite-gold mineralization that occurs within and near the intrusion. The concordant isotopic zircon U-Pb data (301.0 ± 2.6 Ma; MSWD = 2.6) are older than the isotopic zircon U–Pb data previously reported (about 288 Ma). This indicates a substantial extent of the magma emplacement and crystallization process that probably corresponded to several intrusive events or phases, which is a prerequisite for the formation of associated intrusive-related Au deposits. Also, the isotopic age determined highlights the earlier formation of gold-polymetallic-tungsten deposits as compared to Mo–W and Sn-W deposits in the region, which are related to the later Early Permian intrusions. In addition, zircon xenocrysts with much older age (from ca. 970 Ma to ca. 2200 Ma) have been identified; they probably represent the age of the orogenic basement including that of the basement terranes of the Tarim and Karakum cratons. [ABSTRACT FROM AUTHOR]

The age of sedimentation (530–520 Ma) of the Teregtig Formation of South Tuva is estimated on the basis of U–Pb dating of detrital zircon grains from terrigenous rocks and Sr chemostratigraphy of carbonate rocks. It is shown that granitoids with an age of 580 Ma were the main source of detrital zircon. The presence of a representative Precambrian detrital zircon population indicates the deposition of sediments of the Teregtig Formation within the continental crustal block with a long evolution. During the accumulation of coarse-grained rocks of the Teregtig Formation, this part of the eroded area also comprised rocks of the Agardag ophiolite massif, which is evident from numerous angular clasts of olivine, pyroxenes, and Cr-spinels in the conglomerate matrix. [ABSTRACT FROM AUTHOR]

A new locality Kimiltei, Irkutsk oblast, where unmineralized remains of arthropods were buried en masse, is described. The U–Pb zircon dating yielded a Cambrian age with the youngest values of 492 ± 4 Ma. Kimiltei arthropods are represented by Chasmataspidida, Synziphosurina, and Euthycarcinoidea. The last two groups have not been known in the Siberian Platform, and the first one has been described in this area only from Devonian rocks. The Irkutsk findings are the most ancient representatives of their groups, and their distribution areas turn out to be wider than previously known. Their co-burial is noteworthy, because the representatives of these groups have never been found together before. Taking into account the fact that the descendants of all three groups gave rise to the terrestrial lines of chelicerates and insects, the Kimiltei assemblage is the entire fauna of the land arthropod ancestors. Their cohabitation is indicative of the fact that they started their expansion on land from some close ecological niches in the intertidal zone. [ABSTRACT FROM AUTHOR]

Eastern Transbaikalia is a unique rare-metal province of Russia. Most of the studied deposits are associated with granitoid intrusions. Despite the high degree of knowledge of regional magmatism, a number of issues, related to both the belonging of specific massifs to magmatic complexes and the correlation of certain complexes within various structural-formation zones, remain. This paper compares the material composition and age of several petrotypical and parapetrotypical massifs, which are classified as Late Mesozoic complexes distributed within the Aginsk, Shilka, and Argun structural-formational zones of Eastern Transbaikalia. Based on the results of U–Pb dating, two stages of granitoid magmatism have been established: (1) the end of the Middle and the beginning of the Late Jurassic (163–156 Ma) and (2) the beginning of the Early Cretaceous (142 Ma). It is shown that the closely aged rocks of the Borshchovochnyi, Amudzhikan–Sretensk, and Shakhtama complexes have similar material characteristics, while the rocks of the Kukulbei complex (from three massifs) vary in composition. Elevated δ18O values (from +10.8 to +11.9‰) in the rocks of the Jurassic complexes indicate their formation mainly due to the melting of crustal material, and lower δ18O values (from +9.8 up to +10.3‰) in the Early Cretaceous granitoids suggest the contribution of a mantle source to their genesis. [ABSTRACT FROM AUTHOR]

It is established for the first time that biotite plagiogneisses from the Garevka metamorphic complex of the North Yenisei Ridge have geochemical characteristics of C-type adakites with island-arc melt sources. The Hf isotopic composition of zircons indicates the participation of several sources in the formation of the granite melt, including the juvenile mantle and older crustal rock protoliths with model ages THf(DM)с = 1838–1916 and 1965–2357 Ma, respectively. Based on the results of U–Pb dating of zircons, new pulses of Neoproterozoic endogenous activity at the western margin of the Siberian Craton (913 ± 11 and 915 ± 36 Ma for adakite-like granites and 932 ± 26 Ma for leucogranites), correlating with the Grenville tectonic events, were determined. These Grenville episodes of regional crustal evolution are correlated with the synchronous successions and a similar style of tectonothermal events along the Arctic margin of the supercontinent Rodinia. This confirms the spatial proximity of Siberia and the North Atlantic cratons (Laurentia and Baltica), which is consistent with the proposed Neoproterozoic paleogeographic reconstructions of Rodinia. [ABSTRACT FROM AUTHOR]

This paper reports the first discovery of zoned aragonite, a high-pressure CaCO3 polymorph, in a mantle xenolith from kimberlite. Aragonite is the most common epigenetic mineral in the studied xenolith and is located in the interstitial space, where it can occupy up to 80 vol %. According to the P‒T parameters of the last equilibrium (6.9 GPa and 1350°C), the studied sheared lherzolite belongs to the deepest mantle xenoliths from kimberlites. Based on the stability of aragonite, it could have formed in sheared lherzolite both in situ in the lithospheric mantle and during ascent of the kimberlite magma to a depth of ~80 km. The studied aragonite has high contents of SrO (from ~0.7 to 8.3 wt %) and Na2O (up to ~1.1 wt %). Diffusion modeling at mantle temperatures of 1100–1350°C shows that the aragonite grains lose zonation in SrO over ~1–7 years. Thus, the zonation pattern indicates a link between the formation of aragonite in the sheared lherzolite and magmatism, which formed the eastern body of the Udachnaya pipe. In general, such high contents of aragonite in the interstitial space of the studied xenolith are direct evidence of the existence of carbonatite melts in the lithospheric mantle of ancient cratons at depths below ~230 km shortly before the formation of kimberlites on the surface. The results in the present study again raise the question regarding the compositions of primitive kimberlite melts and true concentrations of alkalis (in particular, Na2O) in them. [ABSTRACT FROM AUTHOR]

The first results of the geochronological dating of the specific sill-like gabbrodiorite–granodiorite intrusive bodies within the areal extent of the Paleoproterozoic Ladoga complex, singled out at an early stage of the tectono–metamorphic evolution of the Svecofennides in the southeastern part of the Fennoscandian Shield are presented. Their affinity to the fold-and-thrust paragenetic assemblage of the Meyeri zone, which separates the northern and southern domains of the Ladoga region, in the shape of plated or tabular-like magmatic bodies that fill the feather joints of low-angle thrust faults, is shown. The results of zircon dating by two technologies of the U–Pb method, indicating the time span of the early kinematic stage of the Svecofennian tectogenesis and the according plutonic igneous and metamorphic events at ca. 1.87 Ga, as well as the time limit of the imprinted folding event of the second deformation stage at about 1.83 Ga, are compared. [ABSTRACT FROM AUTHOR]

The original and published geochronological data and the geological position of different granitoid complexes of the Main (Kolyma) Batholith Belt of Northeast Asia have been generalized. It was proved that the belt was formed in two stages. The first Late Jurassic stage of magma generation of granitoids of the Kolyma complex resulted from the collision of island arc and cratonic terranes. This stage was ended with amalgamation of the Kolyma–Omolon superterrane (microcontinent), which is reflected in the U–Pb dating of zircons from granitoids (155–147 Ma). The second, main, stage of the collision of the Siberian continent and the Kolyma–Omolon microcontinent occurred at the boundary between the Jurassic and the Cretaceous. During this stage, intrusions of the Kolyma complex were developed at the upper horizons of the crust, which was proved by the Ar–Ar age estimation (146–133 Ma). The melting out of granitoids of the Nel'kan, Baky-Derbekin, Sakhan'ya, and Omchikandya complexes of the Main Belt with the Early Cretaceous dating for zircon (145–130 Ma) is related to this stage. [ABSTRACT FROM AUTHOR]

The first data of U–Pb isotopic study (LA–ICP–MS method) of zircon from tonalite–granodiorite forming a dominant part of the "trondhjemite" intrusive massif at the giant Tyrnyauz W–Mo deposit (North Caucasus) is presented. The concordant zircon isotopic U–Pb age obtained (302 ± 4 Ma) indicates a Late Paleozoic (Late Carboniferous–Early Permian) age of crystallization of these rocks. This is consistent with the Late Paleozoic epoch of W-bearing magmatism and related W mineralization in the North Caucasus (Peredovoi Ridge) and allows the possibility of the Late Paleozoic age of the large bodies of altered skarn with W mineralization at the Tyrnyauz deposit. [ABSTRACT FROM AUTHOR]

On the basis of petrographic and mineralogical studies, we have established the presence of clastic rocks with a strong predominance of K-feldspar among the rock-forming fragments within the Late Precambrian sedimentary sequence in the southwestern part of the Siberian Platform. Two types of mineralogical occurrence of K-feldspars are determined: (1) huge zonal crystal clasts with increased Ba concentrations in the central parts of the grains and (2) the main mineral phase in the form of a decrystallized glassy mass. In both cases, low concentrations of Na (lower than 0.1 wt %) are detected. K-feldspars of the second type contain intergrowths of idiomorphic rhombic dolomite with a high ankerite component. Dolomite grains contain inclusions of K-feldspar. The prevailing accessory minerals are F-apatite (with high concentrations of REEs), zircon (with high concentrations of Th), magnetite, rutile, monacite, and sinchizite. Encasement minerals with an idiomorphic shape are identified, with K-feldspar being located in the center, while the middle shell is formed by apatite with a high REE content, and the outer shell is formed by apatite without rare earth elements. These rocks are products of high-potassium volcanic activity. The age of this event has been established on the basis of U–Pb zircon dating to about 640 Ma. The Lu–Hf zircon systematics for these rocks indicates the connection of volcanism with igneous events of mantle genesis within its range. The products of explosive eruption, which are widespread within the Biryusa uplift of the Siberian Platform, were erroneously considered earlier as Riphean sedimentary rocks of the Karagas Series. [ABSTRACT FROM AUTHOR]

New mineralogical and isotope–geochemical data for zircon megacrysts (n = 48) from alluvium of Kholomolokh Creek (a tributary of the Ebelakh River) are reported. Using the geochemical classification schemes, the presence of zircons of kimberlitic and carbonatitic genesis was shown. The U–Pb dating of zircons revealed two major age populations: the Triassic (258–221 Ma, n = 18) and Jurassic (192–154 Ma, n = 30). Weighted mean 206Pb/238U ages allowed us to distinguish the following age stages: 155 ± 3, 161 ± 2, 177 ± 1.5, 183 ± 1.5, 190 ± 2, 233 ± 2.5, and 252 ± 4 Ma. It is suggested that the Ebelyakh diamonds could have been transported from the mantle depths by kimberlite, as well as by other related rocks, such as carbonatite, lamprophyre, lamproite, olivine melilitite, etc. Diamonds from the Ebelyakh placers most likely have polygenic native sources and may be associated with polychronous and multistage Middle Paleozoic and Mesozoic kimberlite and alkaline–ultrabasic magmatism in the eastern slope of the Anabar Shield (the Ebelyakh, Mayat, and Billyakh river 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]

The study of granites in the basement of the Western Siberian platform is highly relevant since they are associated with hydrocarbon deposits, which are located not only above the granite massif, but also within the metasomatically altered upper layer of granites. At the same time, granites are most easily and reliably dated by zircon, which makes the geological structure of the area easier to examine, especially when the latter is overlapped by a thick sedimentary cover. The composition of granitoids from the basement of the Traigorod–Kondakovskii licensed site of the Western Siberian megabasin, located in the northwestern part of Tomsk Region, near the border with the Khanty-Mansi Autonomous Okrug, about 40 km east of the village of Aleksandrovskoye, has been studied. This license area is located within the Aleksandrovskii arch, which is bounded by the Ust-Tymsk Depression in the southeast and the Koltogorskii Trough in the northwest. The Aleksandrovskii Arch has a complex structure, which includes the large Krivolutskii granite batholith enclosed in the Carboniferous–Devonian sedimentary (mainly carbonate) rocks and Ordovician–Silurian shales. It has been established that batholith rocks are leucogranites and granites of normal alkalinity and have undergone metasomatic alterations in the form of propylitization and argillization. Granites belong to the I-type and were probably formed from the island arc substrate. Their age, according to the results of U–Pb zircon dating, is approximately 268 Ma; i.e., the generation and intrusion of granites took place during the beginning of the formation of the Koltogorsk–Urengoi Rift, the central rift of Western Siberia (which, according to Ar–Ar basalt dating, was also formed 268 million years ago). [ABSTRACT FROM AUTHOR]

The volcanic–terrigenous Tim Formation in the Kursk Block of Sarmatia occurs in the Paleoproterozoic synforms. The Tim Formation volcanics are represented by metamorphosed ferropicrites, ferropicritic basalts, basalts, and andesibasalts. According to the U–Pb dating of zircon, their possible age is 2099 ± 8 Ma. Thus, the Tim Formation deposits were separated by a long hiatus from the terrigenous–chemogenic strata of the Kursk Group (~2.6–2.4 Ga). Basaltic magmatism is caused by upwelling of melts from the asthenospheric mantle in the slab-window of the subducted oceanic plate during accretion–collisional interaction between the Kursk domain and the Volga–Don orogen. [ABSTRACT FROM AUTHOR]

U–Pb dating of zircons from granitoids located within the Rassokha terrane show a Silurian age of their formation. Younger dates from one of the samples are related to radiogenic lead loss during secondary alteration of the rocks. Based on REE distributions as well as well-defined positive anomalies of K and Pb and negative anomalies of Ba, Sr, Nb, Ta, and Ti, the granitoids are comparable to rocks from supra-subduction environments. Combined with intrusive ages from adjacent areas, Silurian granitoid magmatism of the Rassokha terrane supports the existence of a back-arc basin and a long island arc in Ordovician-Silurian time. [ABSTRACT FROM AUTHOR]

U-Pb dating of zircon from amphibole latite of the central stock of the Nikolka shield volcano in Kamchatka provided the first data on its age. The end of activity falls to about 0.73 Ma (10 analyses). The local U-Pb analyses were carried out at the Isotope Research Center, Schmidt Joint Institute of Physics of the Earth (St. Petersburg) (VSEGEI) using SIMS SHRIMP II. Here, brief information about the geological structure, petrography, and chemistry of the rocks of the volcano are presented. A unique feature of the volcano is the occurrence of a gabbro-anorthosite sheet intrusion with derivates of monzonite and syenite composition in its central part. The correlation of the age obtained with the paleomagnetic data, indicating the formation of the volcano during the magnetic age of Matuyama, is also discussed. The date refers to the period of the change in epochs from the Brunhes to the Matuyama. The obtained age allows dating of the Pliocene volcanic stage in Kamchatka, when large shield volcanoes and plateaus formed. [ABSTRACT FROM AUTHOR]

It is shown that presence of the Early Precambrian sial crust in the Indo-Atlantic segment of the Earth and its absence in the Pacific has been caused by geochemical differences in the mantle underlying these segments. These differences were examined on the basis of Nd-Hf and U-Pb isotopes in modern basalts. The U-Pb isotope system is of particular interest, since uranium is a member of a group of heat-generating radioactive elements providing heat for plumes. It is shown that in the Indo-Atlantic segment, a distribution of areas of the modern HIMU type mantle is typical, while it is almost completely absent in the Pacific segment. In the Archean, in the upper HIMU type paleo-mantle areas, plume generation and formation of the primordial basic crust occurred; this was followed by its remelting resulting in the appearance of an early sial crust forming cratons of the Indo-Atlantic segment. [ABSTRACT FROM AUTHOR]

We have been the first to study in situ the U-Pb isotopic system of aeschynite identified in the gold-bearing magnetite-chlorite-dolomite rocks of the Karabash serpentine massif in the Southern Urals. In the concordia diagram, the U-Pb LA-ICP-MS data on aeschynite are characterized by a considerable discordance, which is consistent with the regression line, the lower crossing of which with the concordia corresponds to an age of 298 ± 18 Ma, whereas the figurative ellipses of coexisting monazite reveal an almost concordant cluster corresponding to the U-Pb age of 317.3 ± 3.3 Ma. It has been established that the closure temperature of the aeschynite system is lower than that of the coexisting monazite. [ABSTRACT FROM AUTHOR]

U-Pb (SIMS) dating of zircons from granite of the Petrokamensk gabbro-granitoid complex, marking termination of the Devonian island-arc magmatism in the Verkhisetsk-Tura Zone of the Middle Urals, gave an age of 386 ± 3 Ma. Zircons from the West Verkhisetsk granitoids, the formation of which corresponds to the beginning stage of magmatism of the continental margin in the region, yielded ages of 386.6 ± 4.1 and 381.8 ± 6.0 Ma. This suggests that the change in the regime of the island-arc geodynamic mode to an active continental margin took place at the boundary of the Middle and Late Devonian. The upper boundary of existence of the continental margin subduction zone is determined by the closure of the Ural paleo-ocean and the beginning of continental collision processes, which resulted in accumulation of flysch in the Ural foreland trough from the second half of the Bashkirian Stage. [ABSTRACT FROM AUTHOR]

Geochemical Sm-Nd isotope and U-Th-Pb geochronological (LA-ICP-MS) studies have demonstrated that the Zeya Group of the Stanovoy Complex of the Dzhugdzhur-Stanovoy Superterrane (Central Asian fold belt) is not Paleoarchean, as was previously thought, but Paleoproterozoic in age. [ABSTRACT FROM AUTHOR]

The results of investigations of gneissose hornblende granitoids, which intrude terrigenous deposits of the Murandav Formation of the Khingan Group and which were deformed together with them due to later structural transformations, are given. It is shown that by their geochemical properties these granitoids are comparable with granitoids of type I and are 535 ± 6 Ma old (U-Pb method on zircons). The obtained data indicate that dikes of hornblende granites, which intrude terrigenous rocks of the Murandav Formation of the Khingan Group and are deformed together with them, were embedded at the Cambrian and Ediacaran transition. The assumption that terrigenous deposits of the Khingan Group (at least the Murandav and underlying Igincha formations) were accumulated in the Neoproterozoic is supported. [ABSTRACT FROM AUTHOR]

Apatite and biotite from dolomite-ankerite and calcite-dolomite carbonatite dikes emplaced into the Paleoproterozoic metamorphic rock complex in the southern part of the Siberian Craton are dated by the U-Pb (LA-ICP-MS) and Ar-Ar methods, respectively. Proceeding from the lower intercept of discordia with concordia, the age of apatite from calcite-dolomite carbonatite is estimated to be 972 ± 21 Ma and that for apatite from dolomite-ankerite carbonatite, as 929 ± 37 Ma. Values derived from their upper intercept have no geological sense. The ages obtained for biotite by the Ar-Ar method are 965 ± 9 and 975 ± 14 Ma. It means that the formation of carbonatites reflects the earliest phases of the Neoproterozoic stage in extension of the continental lithosphere. [ABSTRACT FROM AUTHOR]

Estimates of the P- T parameters of metamorphism, the first results of U-Pb dating of zircons from migmatites of the Teletsk-Chulyshman metamorphic belt, are reported. The age of migmatites from the southern block of the Teletsk-Chulyshman belt is 483.9 ± 5.7 Ma. As is evident from the pressure estimate (≤3-4 kbar), the Chulyshman migmatite-gneiss complex could be an apical part of the thermal-dome structure formed during the Early Ordovician thermal impact of a shallow magmatic basic thermal source, later displaced to the appropriate depth along the thrust at the collisional stage. [ABSTRACT FROM AUTHOR]

Based on geochronological U-Pb studies, the age of Wrangel Island granitoids was estimated as Neoproterozoic (Cryogenian). Some granitoids contain zircons with inherited cores with an estimated age of 1010, 1170, 1200, and >2600 Ma, assuming the presence of ancient (Neoarchean-Mesoproterozoic) rocks in the Wrangel Island foundation and their involvement in partial melting under granitoid magma formation. [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 formation of the Large Igneous Province (LIP) approximately 1380 Ma old in the South Urals was related to the Mashak riftogenic event in the Bashkir meganticlinorium, which was synchronous with the emplacement of different magmatic bodies (the Berdyaush pluton of rapakivi granites and associated rocks, the Main dike of the Bakal ore field, and the Medvedev, Guben, and Kusa massifs, among others) localized among sedimentary deposits of the Burzyan and Yurmatin Groups representing Lower and Middle Riphean type units of northern Eurasia. The U-Pb ID-TIMS age of 1379.6 Ma (MSWD = 1.3) obtained with an accuracy of ±2.9 Ma (confidence interval 95%) combined with the available published U-Pb ID-TIMS data constrain the age and duration of the Early-Middle Riphean pulse in the LIP formation in the Southern Urals. [ABSTRACT FROM AUTHOR]

The U-Pb (SHRIMP) dating of zircon from the layered complex of ophiolitic gabbro in the Klyuchevsk massif yielded an age of 456 ± 6 Ma corresponding within the limits of error to zircon dates obtained for other petrographic varieties from this massif. The investigation of the composition of silicate inclusions in dated zircon grains revealed that they are represented by typical metamorphic minerals: albite, zoisite, and secondary amphiboles. The data indicate that zircon was crystallized during metamorphic transformations of gabbroids and its U-Pb age (Late Ordovician-Silurian) is characteristic of all rocks in the ophiolite association of the Klyuchevsk massif indicating the age of metamorphism, not their formation time. [ABSTRACT FROM AUTHOR]

Here we present the results of U-Pb LA-ICP-MS dating of detrital zircons from the Ediacaran-Early Cambrian deposits of the eastern part of the Baltic monoclise (Leningrad Region). The obtained age spectra of the detrital zircons suggest that, in the Ediacaran-Early Cambrian, the main clastic material source to the northwest of the Russian Platform was the Baltic Shield. Then in the Early Cambrian along with the Baltic Shield provenance, a clastic source from the Timanian margin of Baltica (northeast in modern coordinates) contributed to the deposits. The obtained data either somewhat set limits of the Timanian orogen formation as older than the previously suggested Middle Cambrian (about 510 Ma), based on the 'absence of a Proto-Uralian-Timanian provenance signal' in the Sablino Formation rocks in the south Ladoga, or suggest another rearrangement of detritus transportation paths at the end of Stage 3 (Atdabanian). [ABSTRACT FROM AUTHOR]

Monzogabbrodiorites and monzodiorites from the Tatibin Group of Central Sikhote Alin (Primorye), which hosts the Glukhoe gold ore deposit, are considered with discussion of the most important data on the geological structure and composition of magmatic complexes and the results of U-Pb and SHRIMP dating. It is first established that mineral associations of the gold ore deposit include native Pt, Cu, and other compounds and mineral associations. Their formation conditions of both scientific and practical significance are analyzed. [ABSTRACT FROM AUTHOR]

The U-Pb geochronological data on detrital zircons from placers confined to Neoproterozoic quartzite-schist sequences, which are widespread in the Kokchetav massif of northern Kazakhstan, are discussed. Detrital zircons (332 grains in total) originate from the ore occurrences in the central, northern, and western parts of the massif. The concordant ages of detrital zircons from all the examined occurrences largely correspond to intervals of 1017-1528, 1628-1946, and 2653-2739 Ma. The obtained data imply that material of quartzite-schist sequences of the Kokchetav massif was provided by Mesoproterozoic, Paleoproterozoic, and Neoarchean rock complexes. The lower age limit determined for these sequences is approximately 1.06 Ga. The dates obtained for detrital zircons are most consistent with events that took place in Laurentia. They correspond to the formation and breakup of the Columbia/Nuna supercontinent (approximately 1650-1580 and 1450-1380 Ma ago, respectively) and formation of the Rodinia supercontinent in the period of 1300-900 Ma ago. [ABSTRACT FROM AUTHOR]

The U-Pb dating of zircons from the Mazara granite massif (Southern Urals) by means of the SHRIMP II technique resulted in the conclusion that the zircons were constituted of two key generations belonging, respectively, to the substrate and to the intrusion proper. The age of the granite substrate presented by zircon cores is estimated at 1527-1548 Ma; the final stage of the substrate evolution is characterized by a concordant date of 1388 ± 16 Ma. The latter estimate is much closer to the Mesoproterosoic stage of magmatism. The information on the formation of granites of the Mazara intrusion is mainly contained in the outer parts of the crystals, with two stages distinguished within the formation history. The early and final stages are determined by the datings of 746.6 ± 24.3 and 709.1 ± 5.2 Ma, respectively (both estimates conform to the Neoproterozoic). [ABSTRACT FROM AUTHOR]

This report presents the results of local U-Pb zircon dating (SIMS SHRIMP II) for a sample of migmatite gneiss dredged on the western slope of Alpha Ridge in the Arctic Ocean in the course of the 'Arktika-2012' Russian polar expedition. The distribution of U-Pb ages of the examined zircon points to the Early Precambrian origin of this gneiss, for the bulk of the zircon was crystallized at least 3450 Ma ago from a magmatic melt under acidic volcanism at the primary crust formation. Zircon of the second generation was crystallized 3300 Ma ago under the remelting of acid volcanics and appearance of migmatite gneisses under the amphibolite facies of metamorphism. Most likely, a partial recrystallization of zircon and formation of microfolded structures and foliation took place 3000 Ma ago at the stage of rocks deformation. The latest zircon was formed 1900 Ma ago from the crust fluid or melt under the low-gradient metamorphism. In view of the possibility of the appearance of the treated clastogenic gneiss fragment under current oceanic erosion, the obtained results allow one to affirm that the occurrence of a fragment of the most ancient sialic continental crust formed at least 3450 Ma ago is possible at the submarine rises of the Arctic Ocean (Alpha Ridge and the Mendeleev Rise). [ABSTRACT FROM AUTHOR]

New data on the U-Pb (SHRIMP II) age are obtained for aluminous gneisses of the Kola Group of the Baltic shield. Gneisses are typically ascribed to metasedimentary rocks with detrital zircons. Our work interprets the isotopic data based on the magmatic (tonalite) origin of gneisses and zircon that was established from study of the morphology and geochemistry of zircons. The age of crystallization of the protolith is 2.9 Ga. The existence of two stages of Archean granulite metamorphism is confirmed: an early stage (2.9 Ga) and later granulite metamorphism (2707-2656 Ma). [ABSTRACT FROM AUTHOR]

The article presents a study regarding Uranium-Lead (U-Pb) dating of Zircon from the Chelyabinsk meteorite. Topics include Distribution of rare elements in zircon from the Chelyabinsk meteorite; ,processes that resulted in the formation of zircon grains in the meteorite with the different concentrations of rare and rare earth elements and with the different oxygen isotope compositions; and effect of repeated impacts of the meteorite parental body with other objects on zircon formation.

This report presents the results of U-Pb-geochronological studies (LA-ICP-MS) of detrital zircons from metasedimentary rocks of the west of the Yankan terrane (one of the largest within the structure of the Mongolian-Okhotsk mobile belt). The performed studies ascertain sufficiently the current notions of the geological development of the terrane. It is shown that the rocks are different in age from the main populations of detrital zircons and in the Sm-Nd isotope-geochemical characteristics. In view of this, one may suppose that these rocks do not belong to the unified stratigraphic series but are included into the structures of different-aged accretionary complexes. The terrigenous deposits of the Baldizhak series, as well as those of the Krestovka and Dzhalinda suites, probably belong to the accretionary complexes formed in front of the southeastern margin of the North-Asian craton. On the contrary, the sedimentary formations of the Preobrazhenovka suite are most likely constituents of the accretionary complex formed near the southern margin of the Amur superterrane. The absence of detrital zircons of Mesozoic age in the treated rocks allows one to assume that the considered accretionary complexes were formed during the Paleozoic. [ABSTRACT FROM AUTHOR]

The article discusses a study on formation of geological objects through Uranium - Lead dating and Argon - Argon dating conducted on the Ketkap–Yuna igneous province in Aldan Shield. The study is focussed on the Alkaline volcano - plutonic complexes which shows through isotopic geochronological investigation that there are subalkaline complexes present and are concluded that the oldest of alkaline rocks are volcanic facies.

The U-Pb (LA-ICP-MS) age was determined for detrital zircons from the Upper Triassic volcanomictic rocks of the Osipai Formation (Bulkur River) of the northeastern Siberian Platform. The mineral composition and textural and structural peculiarities of these rocks indicate their formation as a result of eruptive high-potassium trachitic volcanism 235 Ma ago. More local manifestation of this volcanism in the area of the Lena River is evident from the U-Pb age of detrital zircons from the area of the Khatystakh River, which were previously ascribed to the Carnian Stage. Our data indicate redeposition of the clastic material of the Carnian diamond horizon in the post-Jurassic period. [ABSTRACT FROM AUTHOR]

The article discusses a study conducted on Zircons to determine their age through Uranium - Lead dating from an Hypersthene Plagio gneisses mineral which are found in earth's crust. The study was conducted on the Aldan shield area, which indicates volcanogenic composition in them and also indicates that the region underwent granulitic metamorphism.

The article discusses mineralization of Voznesenskoe copper–porphyry deposit in the Main Uralian Fault Zone in Russia. Topics discussed include parental rocks' composition, research on composition of plagiogranite–porphyries, and Uranium–lead (U–Pb) dating of zircons. Other topics include use of Samarium-neodymium (Sm-Nd) dating method and composition of gabbro diorites from the Karagaikul ore.

The article looks at the result of the uranium-lead dating on the age of granitoids in the basement of the Pechora basin in Russia. Topics discussed include formation of granitoid rocks in region, tectonic structure of the basement of the Pechora basin, and deposition of zircons that resulted into formation of rocks.

The article looks at a study done in order to investigate detrital zircons rocks in from paragneiss of the Bulun block in Russia using uranium-lead dating and lutetium-hafnium (lu-hf) isotope systematics. Topic discussed include deformation and metamorphosis up to amphibolite facies of sedimentary volcanogenic rocks, composition and age of metamorphic rocks of the region, and sources of the detrital zircon in the Bulun block metasediments.

The article discusses Uranium-Lead (U-Pb) systematics of Proterozoic magnesites from Satka Deposit, South Urals which provides information on the age and the environment of their formation. It mentions that U-Pb of carbonate rocks it is assumed that the formation of metasomatic magnesite of the Satka deposit occurred during the Middle Riphean.

U-Pb (LA-ICPMS) geochronological studies established the minimum age of detrital zircons from metasedimentary rocks of the Uril Formation of the Amur Group of ∼240 Ma, which approximately corresponds to the lower age boundary of formation of their protoliths. The upper boundary of accumulation of sedimentary rocks of this formation is governed by the age of superimposed structural-metamorphic transformations (220-210 Ma). It follows that the age of protoliths of metasedimentary rocks of the Uril Formation is Triassic in contrast to the previously suggested Early Precambrian age. At the same time, previous estimations of the Nd model age of metasedimentary rocks of the Tulovchikha Formation of the Amur Group and intruding gabbroic rocks are 1.7 and 0.5 Ga, respectively. In other words, the age of this formation is 1.7-0.5 Ga. All of this indicates a combination of sedimentary and volcanic rocks of different ages in the section of the Amur Group. Judging from the Lu-Hf isotopic-geochemical studies of zircons, the major sources of protoliths for metasedimentary rocks of the Uril Formation are Neoproterozoic igneous rocks and also Early and Late Paleozoic and Early Mesozoic igneous rocks, the formation of which was related to the reworking of the Neo- and Mesoproterozoic continental crust. [ABSTRACT FROM AUTHOR]

This paper presents the U-Pb zircon age of pulaskite of the main phase (294 ± 1 Ma) and the rare metal syenite (283 ± 8 Ma) of the Burpala alkaline pluton. The geochronological data show that it was formed in the Early Permian. By age, it is comparable with the Synnyr pluton of the Synnyr rift zone, alkaline granitic rocks and bimodal volcanic associations of the Uda-Vitim rift zone, and carbonatites of the Saizhen rift zone of the Central Asian foldbelt. These intraplate igneous complexes were formed almost simultaneously with crustal granitic rocks of the Angara-Vitim batholite. All of this gives ground to suppose that the origination of their parental melts is a result of the influence of the mantle hot spot or mantle plume on the lithosphere that led to extensive crustal anatexis. [ABSTRACT FROM AUTHOR]

The article discusses a study which presents the first uranium-lead (U-Pb) isotope results of detrital zircons from the Riphean Stratotype of the Southern Urals. It tackles detrital zircon age dating which aims to investigate the age data of strata and deposits. The data gathered shows that at first approximation, zircons can be divided into three populations. It adds that the age spectra difference in zircons show that the Bashkir Meganticlinorium formed due to terrigenous material.

The article focuses on testing the tectonic evolution of the paleozoic sandstones of Polar Urals with the use of uranium-lead (U-Pb) dating of detrital zircons (dZr). It states that the samples were disintegrated manually using mortar and separated in bromoform. It mentions that the results show changes in the sedimentation settings which took place during the Paleozoic period.