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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]

Zircon samples of loess detritus were taken from Qugang loess profile in Maizhokunggar area, southern Tibetan Plateau. Based on the experimental analysis of zircon morphology, trace elements and zircon U–Pb age, provenance information and formation model of Qugang loess were discussed in combination with regional geological, topographic and geomorphological characteristics. The information of zircon morphology and trace elements suggests that the clastic zircons are of magmatic origin and proximal sedimentary characteristics. Zircon U–Pb age spectrum shows that the provenance information is significantly different from loess in the Loess Plateau and the northeastern Tibetan Plateau, related to the distribution of bedrock in regional geology, and corresponding to the Gangdese magmatic activity. The loess sediment development has a "Rock-Valley detrital material-Loess" model. [ABSTRACT FROM AUTHOR]

The research results were received from studying the Pechenga ore-bearing Paleoproterozoic structure, which is located on the northwestern part of the Kola region. The U–Th–Pb zircon age was determined by Secondary Ion Mass Spectrometry (SIMS) on the Sensitive High-Resolution Ion microprobe (SHRIMP-II) spectrometer and Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICPMS) on the ThermoQuest Finnigan MAT Neptune instrument. Basalt conglomerates of the Televi Formation, red gritstones of the Luchlompolo Formation, and high-siliceous turbidites from the middle part of the Matert Formation were tested. On the U–Pb concordia diagram, the part of analytical points for zircon from conglomerates are approximated by the discordia with a top intercept at 2792 ± 7 Ma. All zircon grains from gritstone are located on the concordia. Most of the values of their ages lie within 2700–2820 Ma, and the lesser part of the age values lies within 2840–3000 Ma. Single grains have an age from 3037 ± 4 Ma to 3698 ± 8 Ma. The concordant value of the 207Pb/206Pb age, which is 2640 ± 16 Ma, was established for turbidite zircon. Rocks of the basement at the northern rim of the Pechenga structure: gneisses of the Kirkenes, Varanger, and Svanvik complexes (2715, 2803, and 2825 Ma) and high-aluminous gneisses (2798–2830 Ma) were sources of zircon for conglomerates and gritstones. Granitoids from the southern flank of the structure were sources of zircon for turbidites. The predominant role of the zircon group with an age of 2.7 Ga proves the global increment of the continental crust during this period. The ancient age of zircon (3.0–3.7 Ga) of red-colored gritstones is related to deeper erosion of the basement and exposure of the Eoarchaean and Mezoarchaean rocks at the northern rim during the period of the first global "Oxygen revolution" (2.4–2.3 Ga). [ABSTRACT FROM AUTHOR]

The formation time of 410.5 ± 1.1 Ma (zircon U/Pb SHRIMP) and the duration of rock crystallization (2-2.5 Ma) were determined for gabbro from the Nurali massif. The gabbro zircons showed a complicated polyphase structure. A new polygenous type of zonality including traces of primary growth and of the processes of crushing, dissolution, and substitution was discovered in the zircons. The formations of gabbro and ultramafites (lherzolites) of the massif are separated by a time break of 30-35 Ma determined by the genetic discontinuance. [ABSTRACT FROM AUTHOR]

The results of LA-ICP-MS U-Pb analyses of detrital zircons from the Precambrian deposits of Luga-Ladoga monocline are discussed. The age spectra of the zircons separated from the Riphean to Upper Vendian sandstones from the Shotkusa-1 well demonstrate dominance of the Paleo- and Mesoproterozoic grains while the Archaean zircons are subordinate. The Riphean debris sources were local swells of the Northern Ladoga basement. The sequence interval presumably corresponding to the Vasilieostrov Formation (Upper Vendian) has yielded not only Paleo- and Mesoproterozoic zircon ages, but Neoproterozoic as well, implying a Timanide provenance: these zircons (527 ± 9 and 516 ± 13 Ma) allow deposition of a significant part of the Shotkusa-1 sequence at the very beginning of the Cambrian. [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]

Petrogeochemical and geochronological study of boudined quartzite sandstones and tonalites, as well as host amphibolites, in the shear zone showed that potential sources of detrital zircons were Neoarchean-Paleoproterozoic rocks of the Angara-Kan block and products of their metamorphism. Interpretation of the available data does not confirm the inferred presence of the Early Precambrian basement of the Siberian Craton in the Transangara region. [ABSTRACT FROM AUTHOR]

In order to resolve the age of Navysh volcanics (NV), which is usually attributed to the Lower Riphean of the Ai Formation, we have used geochronological, petrologic, and mineralogical methods of zirconology, apart from the SHRIMP isotopic data of single zircon grains. Moreover, TIMS isotope age analyses have been conducted, the results of which can be regarded as both controlling and providing the most correct information. The TIMS and SHRIMP data make it possible to suggest a polychronous character of the NV, which include not only Riphean, but also Paleozoic groups of volcanics. In this situation, an assessment of the scales of such polychroneity of NV and, correspondingly, of the Ai Formation as a whole becomes urgent. [ABSTRACT FROM AUTHOR]

The problem of the development of the ancient continental crust in the Primorye Region is discussed. It is substantiated by geological and isotope-geochemical criteria: a granite-metamorphic mineral composition of different-aged terrigenous deposits and pelagic cherts, occurrence of arkoses, as well as Proterozoic model age datings of sedimentary complexes and the occurrence of early Proterozoic zircons and monazites. The manifestation of potassium, high-Ba, LREE- and Nb-rich basite-ultrabasite magmatism, typical of Sino-Korean and Okhotsk Ba-bearing nuclears, of lengthy age intervals (Jurassic-Paleogene) in Primorye and the Amur Region is an important criterion. [ABSTRACT FROM AUTHOR]

This paper reports the first results of U-Pb SHRIMP dating of zircon inclusions in sapphire from the Nezametninskii placers in the north of Primorye. The obtained age of paragenesis of these minerals (12.2 ± 0.2 Ma) is almost consistent with the age of erupted alkali basalts in the region, thus evidencing their genetic relation. According to the geochemistry data on trace elements, the dated zircon was crystallized from an alkali basaltic magma or its later trachyte/phonolite derivatives. [ABSTRACT FROM AUTHOR]

The compositional and isotope-geochemical features of zircons from wehrlite of the Feklistov massif, which formed platinum coastal placers, are discussed in this paper for the first time. Zircons from wehrlite of the Feklistov massif, similarly to worldwide zoned clinopyroxenite-dunite massifs, are characterized by different morphology, composition and a wide spectrum of ages (from 2.717 to 0.373 Ga). The Late Devonian age (373.2 ± 7.5 Ma) of zircons allows us to characterize the timing of the formation of wehrlite from the Feklistov massif and to correlate its emplacement with a significant superplume event, which covered the Siberia and Laurussia continents. The geological meaning of this dating refers to limiting the lower age boundary for emplacement of the Feklistov clinopyroxenite-dunite massif into the Earth's crust, which does not contradict geological observations. [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]

This work presents the results of U-Pb isotope dating of zircons from granodiorites and plagiogranites of the Tallainskii gabbro-granodiorite-plagiogranite complex of the Karalon-Mamakan zone of the Baikal-Muya belt, ascribed to the Tallainskii pluton. The age datings obtained for granodiorite of the Eleninskii massif (605 ± 6 Ma) and plagiogranite of the Ust-Berezovo massif (609 ± 6 Ma) are in close agreement within the limits of error. Taking into account previously published data, the emplacement of the Tallainskii complex occurred within the age interval of 615-603 Ma in connection with postcollision extension. The 'island arc' geochemical characteristics of granodiorites and plagiogranites can be explained by magmatic differentiation and (or) participation in the formation of a melt source enriched in the suprasubduction component involved in petrogenesis during the preceding Neoproterozoic period. [ABSTRACT FROM AUTHOR]

Zircons in serpentinites from Nyashevo massif of the Ilmenogorskii complex were dated for the first time by means of the SHRIMP technique. The maximum date of 1892 ± 23 Ma for the zircons accounts for the minimum age of their mantle substrate probably constituting the restite residue. The date is comparable to those for metamorphic rocks of the Selyankino group, as well as of fenite-sand amphibolites of the Ilmenogorskii complex. The Upper Ordovician age limit of 443 ± 12 Ma is adequate for formation of the massif and conforms to the age of the Buldym massif and miaskites. The Early Permian dates of zircons (275.8 ± 2.1 Ma) represent late shear processes in the Ilmenogorskii complex. [ABSTRACT FROM AUTHOR]

The first results of U-Pb dating of detrital zircons from Upper Ordovician sandstones of the Bashkir uplift in the Southern Urals and U-Pb isotopic ages available for detrital zircons from six stratigraphic levels of the Riphean-Paleozoic section of this region are discussed. It is established that the long (approximately 1.5 Ga) depositional history of sedimentary sequences of the Bashkir uplift includes a peculiar period lasting from the Late Vendian to the Emsian Age of the Early Devonian (0.55-0.41 Ga). This period is characterized by the following features: (1) prevalence of material from eroded Mesoproterozoic and Early Neoproterozoic crystalline complexes among clastics with ages atypical of the Volga-Urals segment of the East European Platform basement; (2) similarity of age spectra obtained for detrital zircons from different rocks of the period: Upper Vendian-Lower Cambrian lithic sandstones and Middle Ordovician substantially quartzose sandstones. [ABSTRACT FROM AUTHOR]

Two age stages in the formation of high-aluminous gneisses related to the major stages of granite formation of the Uralian mobile belt were revealed in this study. The first stage (372 ± 2 Ma) corresponds to the age of metamorphism of the amphibolite facies and is controlled by intrusion of the tonalite-trondhjemite series under the environment of the continental margin. At the second stage (307 ± 3 Ma), gneiss underwent contact metamorphism under the influence of plutons of the adamellite-granite composition formed during the early episodes of collisional metamorphism. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates structural position and age justification of neuproterozoic rhyolites of precambrian massif in Central Kazakhstan. Topics discussed include determination of the age of acid volcanic rocks of the Maityubin zone by U-Pb dating method, chemical decomposition of zircon. and separation of uranium (U) and lead (Pb), and isotope study of the accessory zircon.

The article presents study on isotope composition and isomorphic admixture in zircon stimulated treatment in the evolution of the alkaline-carbonatite magmatic system of Il'meno-Vishnevogorskii Complex (IVC) in Urals, Russia. It mentions the use of laser ablation inductively coupled plasma mass spectrometry ((LA-ICP-MS), and trace elements content in zircons of the Il'meno-Vishnevogorskii complex. It adds zircon revealed in miaskite and carbonatite of the IVC.

The article presents a study which analyses results of isotope dating of detrital zircons from sandstones of the low Cambrian Brusov formation of the Southeastern White Sea region. Topics discussed include lower age limit of the beginning of the Arctida-Baltica collision, analysis of the age interval of the crystalline rock complexes, and tectonic nature of orogen.

The volcanic (basaltic, basalt andesitic, andesitic, and rhyolitic) porphyric rocks of the Tsagan-Zaba complex are studied in the Olkhon composite terrane of the Central Asian foldbelt. The concordant U-Pb (SHRIMP-II) age of single zircon grains from rhyolites (492 ± 5 Ma) may be interpreted as the period of formation of the Tsagan-Zaba complex. The volcanic rocks of this complex are characterized by clear suprasubduction geochemical features and positive ɛ( t) values. The similar ages, compositions, and ɛ( t) values of the studied volcanic rocks and gabbroic rocks of the Birkhin pluton allow us to combine them into a common Birkhin volcano-plutonic association, which may be considered as a fragment of a section of the mature island arc of ∼500 Ma in age. The gabbroic rocks may be interpreted as the middle part of this section, whereas the volcanic and volcanosedimentary rocks belong to its upper part. The section was disintegrated 470-460 Ma ago, when the Early Paleozoic island arc was accreted to the southern flank of the Siberian craton in the course of the oblique collision and became a part of the Olkhon composite terrane. [ABSTRACT FROM AUTHOR]

The article discusses the study conducted to examine the early Cretaceous collisional granitoids of the Drevnestanovoi complex from the Selenga-Stanovoi superterrane of the Central Asian mobile belt. Topics discussed include foliation of coarse-grained porphyroid biotite horn blende granites and monzonites, amphibolite-facies conditions, and extraction of zircon from porphyroid biotite hornblende granites.

The article discusses the study conducted on granulite gneiss areas (GGA) and granite greenstone areas (GGSA) as important tectonic elements of the Archean time period to examine the reasons for the early evolution of the Earth. Topics discussed include Pobuzhie granulite complex (PGC) composed in the southwestern part of the Ukraine, information about Granulite UR132 as a glassy and gneissose rock with poor foliation and microbanding, and obtaining age of zircons during recrystallization.

The article presents a research related to zirconology of ultramafic rocks from the Vostochnotagilskii massif (Middle Urals). Topics discussed under research include analysis of mineralogical peculiarities of zircons from ultramafic rocks of the massif and Zircons from dunite showing signs of early and late generations. It reveals that zircons showed clear signs of crushing, recrystallization and idiomorphism.

The Vurechuaivench layered PGE-bearing pluton (VP) is located in the central part of the Kola Peninsula, at the southeastern contact of the Monchegorsk layered complex with the Paleoproterozoic Imandra-Varzuga rift structure. The VP is composed of gabbronorites with a layered horizon of intercalated gabbronorites and anorthosites, containing sulfide and PGE-bearing mineralization. The U-Pb (ID-TIMS) age of baddeleytte from gabbronorite of the ore zone (sample M-42) was determined on a Finningan MAT-262 (RPQ) seven-channel mass-spectrometer in the Laboratory of Geochronology at the Geological Institute, Kola Scientific Center, Russian Academy of Sciences. Zircons from anorthosites and gabbronorites of the ore zone (samples B-1 and B-2, respectively) were studied on a SHRIMP-II secondary-ionic microprobe in the Center of Isotopic Studies of the Federal State Unitary Enterprise VSEGEI (St. Petersburg). The reliable age of formation of various VP rocks was determined by single grains of accessory baddeleytte and zircon based on additional studies of sample M-42 (2498.2 ± 6.7 Ma) and new studies of samples B-1 and B-2 (2507.9 ± 6.6 and 2504.8.4 Ma). The identical U-Pb ages of anorthosites and gabbronorites from the ore reef indicate that anorthosites are a dependent phase and were formed along with gabbronorites during the intrachamber melt differentiation and crystallization. [ABSTRACT FROM AUTHOR]

The article focuses on a study to examine the geodynamic environment of Early Mesozoic magmatism within Mongolia–Transbaikalia region of the eastern part of the Central Asian foldbelt. As per the study, geochronological investigations of granitoids were performed using uranium-lead (U–Pb) method in zircons within Altakhtinskii and Talovskii Complex. The study also revealed that leucogranite of the Altakhtinskii Complex and trachyrhyolite of the Talovskii Complex have the same age of 209–208 Ma.

The article presents a study on the zirconology of dunite contained by Sarany ultramatic complexes such as the Southern and Northern massifs, located in the Middle Urals of Russia. It states that the massifs, which contains chromite ores, were characterized by a strong tectonic violation. It mentions that the age of zircons from dunites of Southern and Northern massifs differs significantly as metasomic alterations in Northern massifs are more intense than that of the Southern massifs.

The article presents information on a study conducted for determination of geochronology of deposition of zircons minerals in Timan Ridge, Russia. The isotopic investigation of the zircon minerals developed from terrigenous rocks in North Timan Ridges in Russia revealed that the rock has been formed in the Riphean geologic timescale. It mentions that the geologic age of the zircon minerals were analyzed through uranium-lead dating method. The study also revealed that the rocks in North Timan Ridges in Russia are largely composed of pelites, silt stones and sandstones.

The article estimates the age of the rocks of Solzan granitoid massif of the Khamar-Daban Province in Baikal, Russia using uranium-lead dating method. It analyzes the composition of the massif in the eastern which include granodiorite-gneiss and granite with amphibole, biotite, or garnet in dependence on the composition of host gneiss. It examines the accessory zircons that were extracted from samples representing biotite and garnet-biotite biotite leucogranites of layered bodies from the eastern part of the massif. It cites the uranium-lead dating of zircons which showed that magmatic zircons from granite melts in the Solzan massif started to crystallize 516-515 million years ago.

The article discusses the study conducted for the reconstruction of Late mesozoic provenances for the east Asian continental margin based on Uranium (U) Lead (Pb) detrital zircon geochronology. Topics discussed include investigation done using facies analysis, petrography, and lithochemistry, dating of detrital zircons using laser ablation inductively coupled plasma mass spectrometry, and metasedimentary rocks with subordinate volcanics.