Age and origin of the corundum-bearing rocks of Khitostrov Island, Northern Karelia     

D. P. Krylov  E. B. Sal’nikova  A. M. Fedoseenko  S. Z. Yakovleva  Yu. V. Plotkina  I. V. Anisimova 《Petrology》2011,19(1):79-86

The Chupa nappe of the Belomorian Complex contains aluminous silica-undersaturated rocks with corundum, which are characterized by extremely low ¹⁸O/¹⁶O (whole-rock δ¹⁸O up to −21‰). Revealed isotopic anomalies are explained by the influence of meteoric waters that were modified through evaporation-precipitation cycles (Rayleigh distillation) under cold climatic conditions. In order to estimate whether the decrease in δ¹⁸O occurred prior to metamorphism of the protoliths of the Chupa Sequence or during water percolation in the course of metamorphic or postmetamorphic transformations, we studied oxygen composition in the rocks and minerals and conducted U-Pb dating on single zircons from corundumbearing rocks of Khitostrov.  相似文献   

Late Carboniferous Monzonite–Granosyenite Magmatism in the Northern Balkhash Region (Central Kazakhstan)     

P. V. Ermolov  K. E. Degtyarev  E. B. Salnikova  A. A. Tretyakov  A. B. Kotov  I. V. Anisimova  Yu. V. Plotkina 《Doklady Earth Sciences》2018,478(2):156-160

U–Pb dating of the Torangalyk Complex (Northern Balkhash) yielded a Late Carboniferous age of 305 ± 2 Ma. Taking into account the previous data, a new scheme for Late Paleozoic granitic magmatism in this region has been proposed. It includes the Early Carboniferous granite–granodiorite Balkhash Complex, Late Carboniferous monzonite–granosyenite Kokdombak and Torangalyk complexes, and the Late Carboniferous–Early Permian granite–leucogranite Akchatau Complex.  相似文献   

New Data on the Age of the Tonalite–Trondhjemite Orthogneisses of the Olekma Complex of the Central Part of the Chara–Olekma Geoblock,Aldan Shield     

S. D. Velikoslavinskii  A. B. Kotov  E. B. Sal’nikova  A. B. Kuznetsov  V. P. Kovach  N. V. Popov  E. V. Tolmacheva  I. V. Anisimova  Yu. V. Plotkina 《Doklady Earth Sciences》2018,482(2):1265-1269

New U–Pb zircon (TIMS) results allow dating of protoliths of tonalite–trondhjemite orthogneisses of the Olekma Complex in the central part of the Chara–Olekma Geoblock (Aldan Shield) to 2825 ± 3 Ma and 2994 ± 3 Ma. Together with the results of previous geochronological studies, this proves that the Olekma Complex comprises heterochronous igneous rocks intensively reworked under amphibolite facies conditions and formed during different stages of geological evolution of the Aldan Shield.  相似文献   

Age and Tectonic Settings of the Usugli Depression Volcanics and Dotulur Alkalic Granite (West Transbaikalia)     

A. M. Larin  A. B. Kotov  E. B. Salnikova  E. V. Sklyarov  A. M. Mazukabzov  I. V. Anisimova  E. V. Tolmacheva  Yu. V. Plotkina 《Doklady Earth Sciences》2018,482(2):1293-1297

The Dotulur alkalic granite and Usugli Depression volcanics (West Stanovoi Superterrane of the Central Asia Fold Belt) have been dated by the U–Pb method, and their geochemistry has been analyzed. The geochemistry of the rocks suggests their intraplate nature. The alkalic granite and volcanics have similar ages of 142 ± 1 Ma and 138 ± 3 Ma, respectively. Considering the Usugli Depression structural position as an upper fault slice of the Elikan metamorphic core, the obtained dates allow the formation of the mentioned core and, accordingly, the collapse of central part of the Mongol–Okhotsk orogeny to have occurred not prior to 140 Ma.  相似文献   

Crystallogenesis of zircon in alkaline granites and specifics of zircon U-Pb dating: A case study of the Khangai magmatic area     

E. B. Sal’nikova  S. Z. Yakovleva  A. B. Kotov  E. V. Tolmacheva  Yu. V. Plotkina  A. M. Kozlovskii  V. V. Yarmolyuk  A. M. Fedoseenko 《Petrology》2014,22(5):450-461

Data obtained on the Khangai zonal magmatic areole in the Central Asian Orogenic Belt indicate that accessory zircons in alkaline granitoids have crystallogenetic characteristics that generally reflect specifics of the evolution of the parental alkaline magmas. The late differentiation of these magmas was characterized by an increase in the concentrations of trace and rare-earth elements, water, and fluorine in the residual melts and aqueous salt-bearing fluids. Their action was associated with local transformations of the zircon, first and foremost, with local enrichment of zircon crystals in fluid inclusions and in crystalline inclusions of sulfides an other ore minerals. This disturbed the Pb isotopic composition of the zircon, for example, led to its enrichment in common (admixture) Pb and thus caused significant errors and uncertainties in the U-Pb zircon dates. Our recently obtained data indicate that one of the most efficient methods of preparing accessory zircons enriched in common Pb to their U-Pb dating is their preparatory treatment with acids (Makeev, 1981; Mattinson, 1994, 1997, 2005). The application of this technique makes it possible to rid the zircons of phases enriched in common Pb and usually to obtain reliable geochronologic data. The method of preparatory acid treatment of zircons is thus best suitable for geochronologic studies of granitoids of elevated alkalinity.  相似文献   

The time length of formation of the Angara-Vitim batholite: Results of U-Pb geochronological studies     

V. P. Kovach  E. B. Sal’nikova  E. Yu. Rytsk  V. V. Yarmolyuk  A. B. Kotov  I. V. Anisimova  S. Z. Yakovleva  A. M. Fedoseenko  Yu. V. Plotkina 《Doklady Earth Sciences》2012,444(1):553-558

This paper describes the results of geochronological studies (U-Pb method over micro lots and single grains of zircon) of autochtonous and allochtonous granitoids of the Barguzinskii complex of the Angara-Vitim batolite of the petrotypical area in the basin of the Dzhirga and Kovyli rivers (tributaries of the Barguzin River). The age of crystallization of gneissose granitoids is 297 ± 5 Ma, and that of intrusive leucocratic biotite granites is 291 ± 1 Ma. The estimates of the age finalize the discussion on the age of granitoids of the Barguzin complex and cannot be considered as ??rejuvenated.?? The analyses of the geochronological data that have been obtained up to the present for granitoids of the Angara-Vitim batolite with the SHRIMP and U-Pb methods for large samples of zircons show that in the majority of cases they cannot be used for precise estimation of the age of their crystallization. The geochronological data obtained with use of the U-Pb method over micro samples and single grains of zircon allow one to make a conclusion on the formation of granitoids of the described complexes of the Angara-Vitim batholite that occurred within 303 ± 7?C281 ± 1 Ma. Thus, the time length of formation of the largest in the eastern segment of the Central Asian belt of the Angara-Vitim batholite is not more than 22 Ma (minimum 6 Ma), which allows us to consider it as a large granitic province and is a boundary condition for development of the geodynamic models of its formation.  相似文献   

Stages and regularities in the development of Late Paleozoic anorogenic volcanism in the southern Mongolia Hercynides     

A. M. Kozlovsky  V. V. Yarmolyuk  A. V. Travin  E. B. Sal’nikova  I. V. Anisimova  Yu. V. Plotkina  V. M. Savatenkov  A. M. Fedoseenko  S. Z. Yakovleva 《Doklady Earth Sciences》2012,445(1):811-817

  相似文献   

Convergent boundaries and related igneous and metamorphic complexes in caledonides of Central Asia     

I. K. Kozakov  E. B. Sal’nikova  V. V. Yarmolyuk  A. M. Kozlovsky  V. P. Kovach  P. Ya. Azimov  I. V. Anisimova  V. I. Lebedev  G. Enjin  Ch. Erdenejargal  Yu. V. Plotkina  A. M. Fedoseenko  S. Z. Yakovleva 《Geotectonics》2012,46(1):16-36

Fragments of the crystalline complexes where Vendian metamorphism of moderate and elevated pressure predated Early Paleozoic metamorphism have been established in the accretionary-collisional domain of the eastern segment of the Central Asian Foldbelt (Early Caledonian superterrane of Central Asia). The geodynamic setting of the Vendian (??560?C570 Ma) South Hangay metamorphic belt located in the junction zone of the Baydrag Block and the Late Riphean (??665 Ma) ophiolite complex of the Bayanhongor Zone is considered. The origination of this belt was related to the formation of the convergent boundary in the framework of the Zabhan microcontinent about 570 Ma ago. At the same time, an island-arc complex was formed in the paleo-oceanic domain. Metamorphism of elevated pressure indicates that Vendian structures with sufficiently thick continental crust were formed in the framework of the continental blocks. Vendian metamorphism is also established in the Tuva-Mongolia Massif and the Kan Block of the Eastern Sayan. These data show that the Late Baikalian stage predated the evolution of the Early Caledonian superterrane of Central Asia. The development of its accretionary-collisional structure was accompanied by Late Cambrian-Early Ordovician low-pressure regional metamorphism. Granulite-facies conditions were reached only at the deep levels of the accretionary-collisional edifice. The outcrops of crystalline complexes in the southern framework of the Caledonian paleocontinent are regarded as fragments of the Early Paleozoic Central Mongolian metamorphic belt.  相似文献   

Sources and Provenances of Late Cenozoic Sand Deposits of the Ol’khon Island (Baikal Rift Zone)     

Kotov  A. B.  Skovitina  T. M.  Kovach  V. P.  Sklyarov  E. V.  Donskaya  T. V.  Lopatin  D. V.  Plotkina  Yu. V.  Tolmacheva  E. V.  Gorokhovskii  B. M.  Buchnev  I. N. 《Doklady Earth Sciences》2019,484(1):45-47

Doklady Earth Sciences - Geochronological (LA–ICP–MS) U–Th–Pb studies of detrital zircon of the Late Cenozoic sand deposits on Ol’khon Island have been performed. It...  相似文献   

The Early Cambrian Age and Crustal Sources of Granitoids of the Goryachinskiy Pluton (Northern Baikal): Geodynamic Implications     

Rytsk  E. Yu.  Salnikova  E. B.  Yarmolyuk  V. V.  Andreev  A. A.  Bogomolov  E. S.  Lebedeva  Yu. M.  Velikoslavinsky  S. D.  Anisimova  I. V.  Plotkina  Yu. V.  Fedoseenko  A. M. 《Doklady Earth Sciences》2019,484(2):163-166

Doklady Earth Sciences - New results of U–Pb zircon and Nd–isotope analyses of the Goryachinskiy Pluton adakite granites have been obtained. The pluton is exposed along the Baikal coast...  相似文献