Age of the Vishnyakovskoe deposit of rare-metal pegmatites (East Sayan): U-Pb geochronological study of manganotantalite     

E. B. Sal’nikova  A. M. Larin  S. Z. Yakovleva  A. B. Kotov  V. A. Glebovitskii  A. V. Tkachev  I. V. Anisimova  Yu. V. Plotkina  B. M. Gorokhovskii 《Doklady Earth Sciences》2011,441(1):1479-1483

The U-Pb age of the manganotantalite from rare-metal pegmatites of the Vishnyakovskoe deposit (East Sayan Belt) has been assessed at 1838 ± 3 Ma. The acquired data indicate the pegmatites of this deposit and associated granites of the Sayan complex belong to the postcollision South Siberian igneous belt (1.88–1.84 Ga), which stretches along the southwestern frame of the Siberian Craton by more than 2500 km, from the Yenisei Ridge to the Aldan Shield. Formation of this igneous belt is related to joining (starting from about 1.9 Ga BP) of the series of continental microplates and island arcs to the Siberian Craton; this led to final stabilization of the craton at about 1.8 Ga BP.  相似文献   

Sources of the Jurassic terrigenous rocks of the Upper Amur and Zeya–Dep troughs of the eastern part of the Central Asian fold belt: Results of Sm–Nd isotopic–geochemical and U–Pb (LA-ICP-MS) geochronological studies     

Yu. N. Smirnova  A. A. Sorokin  A. B. Kotov  V. P. Kovach 《Doklady Earth Sciences》2015,465(2):1224-1228

The results of U–Pb geochronological studies of detrital zircons and Sm–Nd isotopic–geochemical studies of terrigenous rocks of the Upper Amur and Zeya–Dep troughs indicate that the beginning of orogenic processes, which led to the formation of the Mongol–Okhotsk fold belt, occurred in the Early Jurassic.  相似文献   

Composition, sources, and mechanism of continental crust growth in the Lake zone of the Central Asian Caledonides: I. Geological and geochronological data     

V. V. Yarmolyuk  V. P. Kovach  V. I. Kovalenko  E. B. Salnikova  A. M. Kozlovskii  A. B. Kotov  S. Z. Yakovleva  A. M. Fedoseenko 《Petrology》2011,19(1):55-78

Data on the composition, inner structure, and age of volcanic and siliceous-terrigenous complexes and granitoids occurring in association with them in the Caledonian Lake zone in Central Asia are discussed in the context of major relations and trends in the growth of the Caledonian continental crust in the Central Asian Foldbelt (CAFB). The folded structures of the Lake zone host basalt, basalt-andesite, and andesite complexes of volcanic rocks that were formed in distinct geodynamic environments. The volcanic rocks of the basalt complex are noted for high concentrations of TiO₂ and alkalis, occur in association with fine-grained siliceous siltstone and siliceous-carbonate rocks, are thus close to oceanic-island complexes, and were likely formed in relation to a mantle hotspot activity far away from erosion regions supplying terrigenous material. The rocks of the basalt-andesite and andesite complexes have lower TiO₂ concentrations and moderate concentrations of alkalis and contain rock-forming amphibole. These rocks are accompanied by rudaceous terrigenous sediments, which suggests their origin in island-arc environments, including arcs with a significantly dissected topography. These complexes are accompanied by siliceous-terrigenous sedimentary sequences whose inner structure is close to those of sediments in accretionary wedges. The folded Caledonides of the Lake zone passed through the following evolutionary phases. The island arcs started to develop at 570 Ma, their evolution was associated with the emplacement of layered gabbroids and tonalitetrondhjemite massifs, and continued until the onset of accretion at 515–480 Ma. The accretion was accompanied by the emplacement of large massifs of the tonalite-granodiorite-plagiogranite series. The postaccretionary evolutionary phase at 470–440 Ma of the Caledonides was marked by intrusive subalkaline and alkaline magmatism. The Caledonides are characterized by within-plate magmatic activity throughout their whole evolutionary history, a fact explained by the accretion of Vendian-Cambrian oceanic structures (island arcs, oceanic islands, and back-arc basins) above a mantle hotspot. Indicators of within-plate magmatic activity are subalkaline high-Ti basalts, alkaline-ultrabasic complexes with carbonatites and massifs of subalkaline and alkaline gabbroids, nepheline syenites, alkaline granites, subalkaline granites, and granosyenites. The mantle hotspot likely continued to affect the character of the lithospheric magmatism even after the Caledonian folded terrane was formed.  相似文献   

One-meter Schmidt telescope of the Byurakan Astrophysical Observatory: New capabilities     

S. N. Dodonov  S. S. Kotov  T. A. Movsesyan  M. Gevorkyan 《Astrophysical Bulletin》2017,72(4):473-479

In 2013–2015 the Laboratory of spectroscopy and photometry of extragalactic objects (LS-PEO) of the Special Astrophysical Observatory together with Armenian specialists upgraded the 1-m Schmidt telescope of the Byurakan Astrophysical Observatory of the National Academy of Sciences of Armenia. We completely redesigned the control system of the telescope: we replaced the actuating mechanisms, developed telescope control software, and made the guiding system. We reworked and prepared a 4k × 4k Apogee (USA) liquid-cooled CCD with RON ~ 11.1 e^?, a pixel size of 0.″868, and field of view of about 1□°, and in October 2015 mounted it in the focus of the telescope. The detector is equipped with a turret bearing 20 intermediate-band filters (FWHM = 250 Å) uniformly covering the 4000–9000 Å wavelength range, five broadband filters (u, g, r, i, z SDSS), and three narrow-band filters (5000 Å, 6560 Å and 6760 Å, FWHM = 100 Å). During the first year of test operation of the 1-m telescope we performed pilot observations within the framework of three programs: search for young stellar objects, AGNevolution, and stellar composition of galaxy disks.We confirmed the possibility of efficiently selecting of young objects using observations performed in narrow-band Hα and [SII] filters and the intermediate-band 7500 Å filter. Three-hours long exposures with SDSS g-, r-, and i-band filters allow us to reach the surface brightness level of 28^m/□″ when investigating the stellar content of galaxy disks for a sample of nine galaxies. We used observations performed with the 1-m telescope in five broadband (SDSS u, g, r, i, and z) and 15 intermediate-band filters (4000–7500 Å) to construct a sample of quasar candidates with 0.5 < z < 5 (330 objects) in about one-sq. degree SA68 field complete down to R_AB = 23^m. Spectroscopic observations of 29 objects (19.^m5 < R < 22^m) carried out at the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences confirmed the quasar nature of 28 objects.  相似文献   

The Late Silurian Age of the Reference Aralaul Granosyenites–Granite Massif (Northern Kazakhstan)     

K. E. Degtyarev  A. A. Tretyakov  A. B. Kotov  E. B. Salnikova  M. V. Luchitskaya  V. P. Kovach  K.-L. Wang 《Doklady Earth Sciences》2018,479(1):275-278

This work presents the results of U–Pb geochronological studies of alkaline granites of the Aralaul complex of Northern Kazakhstan, which allow one to substantiate their Late Silurian (420 ± 4 Ma) age. Taking into consideration the previously obtained data, we propose a new development scheme of Paleozoic granitoid magmatism in Northern Kazakhstan, which includes Late Ordovician granite–granodiorite (Zerenda and Krykkuduk), Early Silurian granite–leucogranite (Borovoe and Karabulak), Late Silurian granosyenites–granite (Aralaul), and Early Devonian (Balkashino and Orlinogorsk) complexes.  相似文献   

Determining the Geodynamic Setting of Adakitic Granitoids Using Geochemical Data     

S. D. Velikoslavinskii  A. B. Kotov  D. P. Krylov  A. M. Larin 《Petrology》2018,26(3):255-264

Discriminant analysis was performed for representative sets of igneous rocks with adakitic geochemical signatures (granitoids of Archean tonalite–trondhjemite–granodiorite suites, island-arc adakites, and adakites and adakitic granitoids of collisional to postcollisional geodynamic settings). It was shown that the granitoids of Archean tonalite–trondhjemite–granodiorite suites are significantly different from islandarc adakites, as well as from collisional to postcollisional adakites and adakitic granitoids. The following discriminant function was proposed for the geodynamic classification of island arc and collisional-postcollisional adakites and adakitic granitoids on the basis of chemical composition: DF₃ =–1.69324TiO₂–0.25537Al₂O₃–0.21269FeO* + 0.06076MgO–0.09796CaO + 0.47377Na₂O + 0.29270K₂O + 3.57821P₂O₅ + 0.00431Rb + 0.00036Sr + 0.03119Y + 0.00006Zr + 0.01088Nb–0.00048Ba + 0.01366La + 0.0004Ce + 0.02319Nd–0.18584Sm + 1.29135Eu–0.62229Gd + 0.3819Dy + 2.06583Er–2.62769Yb + 1.6464.  相似文献   

Genesis of the Paleoproterozoic Rare-Metal Granites of the Katugin Massif     

T. V. Donskaya  D. P. Gladkochub  E. V. Sklyarov  A. B. Kotov  A. M. Larin  A. E. Starikova  A. M. Mazukabzov  E. V. Tolmacheva  S. D. Velikoslavinskii 《Petrology》2018,26(1):47-64

We studied the petrography, mineralogy, and geochemistry of the Paleoproterozoic (2.06 Ga) granites of the Katugin massif (Stanovoy suture zone), which hosts the combined rare-metal Katugin deposit. Three groups of granites were distinguished: (1) biotite (Bt) and biotite–riebeckite (Bt–Rbk) granites of the western block of the massif; (2) biotite–arfvedsonite (Bt–Arf) granites of the eastern block; and (3) arfvedsonite (Arf), aegirine–arfvedsonite (Aeg–Arf), and aegirine (Aeg) granites of the eastern block. The Bt and Bt–Rbk granites of the first group are mainly metaluminous and peraluminous rocks with rather high CaO contents and the minimum F contents among the granites described here. It was suggested that the granites of this group could be derived from a source dominated by crustal rocks with a small addition of mantle materials. These granites probably crystallized from a metaluminous–peraluminous melt with elevated CaO and moderate F contents. Melts of such compositions are least favorable for the crystallization of ore minerals. The Bt–Arf granites of the second group are mainly peralkaline and show high contents of CaO and Y and low contents of Na₂O and F. A mixed mantle–crust source was proposed for the Bt–Arf granites. The initial melt of the Bt–Arf granites could have a peralkaline composition with elevated CaO content and moderate to high F content. The Arf, Aeg–Arf, and Aeg granites of the third group are enriched in ore mineral and were classified as peralkaline granites with very low CaO contents, elevated Na2O and F contents, and usually very high contents of Zr, Hf, Nb, and Ta. Based on the geochemical and isotopic data, it was supposed that the source of the granites of the third group could be derivatives of basaltic magmas produced in an OIB-type source with a minor addition of crustal material to the magma generation zone. It was suggested that the primary melt of this granite group could be a peralkaline CaO-poor and F-rich silicic melt, which is most favorable for the crystallization of ore minerals. Based on the analysis of the geochemical characteristics of the three granite groups and their relationships within the Katugin massif, a qualitative model of its formation was proposed. According to this model, the Bt and Bt–Rbk granites of the western block crystallized first, followed by the Bt–Arf granites of the eastern block and, eventually, the Arf, Aeg–Arf, and Aeg granites enriched in ore minerals.  相似文献   

Granitoids of the Kongo Magmatic Zone of the Omolon Massif (Northeastern Russia): Rock Composition,Age, and Geodynamic Setting     

Glukhov  A. N.  Kotov  A. B.  Priymenko  V. V.  Sal’nikova  E. B.  Ivanova  A. A.  Plotkina  Yu. V.  Fedoseenko  A. M. 《Geotectonics》2022,56(2):178-190

Geotectonics - In our study we analyzed the composition of granitoid rocks within the Kongo magmatic zone of the Omolon median mass. The studied calc-alkaline granitoids cut through the Early...  相似文献   

Age of the Ust’-Gilyui sequence in the Stanovoi Complex of the Selenga-Stanovoi Superterrain, Central Asian fold belt     

S. D. Velikoslavinskii  A. B. Kotov  E. B. Salnikova  A. M. Larin  A. A. Sorokin  A. P. Sorokin  V. P. Kovach  E. V. Tolmacheva  S. Z. Yakovleva  I. V. Anisimova 《Doklady Earth Sciences》2012,444(2):661-665

According to the results of U-Pb geochronological investigations, the age of the amphibolite protoliths (metabasalts) in the Ust??-Gilyui sequence within the Stanovoi Complex of the Amazar-Gilyui structural and formational zone in the Selenga-Stanovoi Superterrain of the Central Asian fold belt can be estimated at 193 ± 1 Ma. The Nd model age of the Ust??-Gilyui metasedimentary rocks is in the interval of t _Nd(DM) = 1.1?C3.1 Ga. This information along with the previously obtained geochronological data are indicative of the fact that the Ust??-Gilyui sequence consists of metasedimentary and metavolcanic rocks of various ages: (1) volcanic rocks with the age of 193 ± 1 Ma; (2) metasedimentary and metavolcanic rocks broken through by the Paleozoic granitoids dated to 370 Ma and characterized by minimum estimations of t _Nd(DM) = 1.1 Ga, i.e., rocks with an age of 1.1?C0.4 Ga. In addition, it is quite possible that this sequence also includes more ancient rocks. The SSS Amazar-Gilyui structural and formational zone is likely to be a tectonic mélange composed of the metasedimentary and metavolcanic rocks of the Mesozoic and, probably, Paleozoic and Early Precambrian ages. The studied zone was formed in the Mesozoic, most likely, in the course of the collision processes initiated by the closing up of the Mongol-Okhotsk Ocean.  相似文献   

Sources of the Late Mesozoic magmatic associations in the northeastern part of the Amurian microcontinent     

A. A. Sorokin  A. B. Kotov  V. P. Kovach  V. A. Ponomarchuk  V. M. Savatenkov 《Petrology》2014,22(1):65-76

Based on generalization of available geochronological data, Late Mesozoic magmatic associations in the northeastern part of the Amurian microcontinent are divided into three groups: 142–125, 124–115, and <110 Ma. The age of these associations decreases with approaching the Pacific margin of Asia. In the same direction, they show a change in sources of their parental melts: continental crust (142–125 Ma) → continental crust + PREMA (DM) (124–115 Ma) → continental crust + PREMA (DM) + EMII (<110 Ma). Isotope-geochemical (Sr-Nd) study indicates that intrusive and volcanic rocks of the Late Mesozoic magmatic associations in the northeastern part of the Amurian microcontinent were originated in geodynamic settings that provided access of enriched mantle sources to magma formation. The most probable of these settings are as follows: (1) plate sliding accompanying by the formation of slab window beneath continental margin; (2) passage of the Asian margin over the East Asian mantle hot field in the Late Mesozoic; (3) asthenospheric upwelling due to delamination of the lower crust during closure of the Mongolian-Okhotsk ocean caused by collision between the Amurian microcontinent, Dzhugdzhur-Stanovoy, and Selenga-Stanovoy superterranes in the Central Asian fold belt.  相似文献