Potential volcanic danger in the Keli highland (Greater Caucasus): Evidence from isotopic-geochronological study of the youngest lavas     

V. A. Lebedev  G. T. Vashakidze  V. G. Sakhno 《Doklady Earth Sciences》2008,418(1):169-173

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Age,main geochemical characteristics,and sources of late Cenozoic volcanic rocks in the Udurchukan volcanic area (Amur Region)     

A. A. Chashchin  A. A. Sorokin  V. A. Lebedev  M. G. Blokhin 《Russian Journal of Pacific Geology》2016,10(4):239-248

This paper presents new mineralogical, petrographic, geochemical, and isotope–geochronological data on the Cenozoic basaltic trachyandesites from the Udurchukan volcanic area (Amur region), which occupies the watersheds of the Uril, Mutnaya, and Khingan rivers. Based on the available geochrolonological data and new K–Ar dating, the basaltic trachyandesites are middle Miocene in age (18.9–17.1 Ma). Petrogeochemically, they are divided into two groups. These groups differ in the contents of MgO, TiO₂, P₂O₅, as well as Sr, Ba, Nb, Ta, and LREE, which is presumably related to the different degrees of metasomatic reworking of the mantle sources and their melting. In terms of the trace-element distribution and ratios, the basaltic trachyandesites from the Udurchukan area are close to the within-plate rocks and were contributed by enriched lithospheric mantle previously subjected to fluid metasomatism.  相似文献   

A MECHANICAL MODEL OF THE DEFORMATION OF CARTOGRAPHIC PAPER IN A DIRECTION PERPENDICULAR TO ITS SURFACE     

T. G. Ivanova  Yu. M. Lebedev  A. P. Sokol  S. G. Markova 《地理信息系统科学与遥感》2013,50(2):154-159

The mathematical basis for analyzing the dimensional stability of cartographic drafting surfaces, and more specifically paper, is presented in the form of a simple mechanical model. Deduction from a universal equation incorporating such factors as elasticity, viscosity, and relaxation time yields less general but more applicable equations once assumptions are made about which factors are dominant and, on the other hand, insignificant. Translated from: Izvestiya vysshykh uchebnykh zavedeniy, Geodeziya i aerofotos” yemka, 1986, No. 4, pp. 106-111.  相似文献   

U-Pb zircon age of gabbroids of the Ust’-Belaya mafic-ultramafic massif (Chukotka) and its interpretation     

G. V. Ledneva  B. A. Bazylev  V. V. Lebedev  N. N. Kononkova  A. Ishiwatari 《Geochemistry International》2012,50(1):44-53

The Ust’-Belaya mafic-ultramafic massif is assigned to the Western Koryak fold belt and largely composed of residual spinel peridotites, layered spinel and plagioclase peridotites, and gabbros. These rocks are crosscut by occasional plagiogranite and diorite veins and exhibit locally a close spatial association with basalts and carbonate-sedimentary deposits of Late Devonian and Early Carboniferous age. Based on this evidence, the massif was ascribed to the pre-Late Devonian ophiolite association. Our study presents new U-Pb SHPIMP II zircon ages and petrographic and mineralogical data on samples of the layered amphibole gabbro and vein diorite from the Ust’-Belaya massif. The approximate concordant U-Pb age corresponding to a timing of of amphibole gabbro crystallization is 799 ± 15 Ma, and the concordant U-Pb age reflecting a timing of of vein diorite crystallization is 575 ± 10 Ma. These ages coupled with geological studies of the massif, petrological and mineralogical investigations of the dated samples, as well as literature data on the petrology of peridotites and the age of formed plagiogranites suggest that the peridotites and layered gabbros of the Ust’-Belaya massif were formed by the Late Riphean, whereas the vein diorite and plagiogranite were resulted from a later (Vendian-Cambrian) magmatic stage. The peridotites and gabbros of the massif display no genetic relationship with spatially associated basalts and sedimentary rocks and, thus, they cannot be considered as members the pre-Late Devonian ophiolitic association. The results of this study will inevitably lead to a significant revision of geological and geodynamic interpretations of the Ust’-Belaya mafic-ultramafic massif. However, uneven study of the Precambrian complexes of the Koryak and Chukchi areas, their evolution in different structures of the region cannot yet be described by a single geodynamic scenario.  相似文献   

Age and origin of Miocene gabbroid intrusions in the northern part of the Lesser Caucasus     

V. A. Lebedev  I. V. Chernyshev  G. T. Vashakidze  Yu. V. Goltsman  T. I. Oleinikova  A. I. Yakushev 《Petrology》2014,22(6):521-535

The results of isotope-geochronological and petrological-geochemical study are reported for Neogene mafic intrusive rocks distributed in the northern part of the Lesser Caucasus (Georgia). It is shown that the young plutonic bodies were formed here in two magmatic stages: in the Middle Miocene (around 15.5 Ma) and in the terminal Miocene (9-7.5 Ma). The first age group includes a microsyenitic massif in Guria (Western Georgia), which was formed in a setting of active continental margin related to the subduction of oceanic part of the Arabian plate beneath the Transcaucasus. The Late Miocene intrusive magmatism already records the incipient within-plate activity: small polyphase bodies of alkaline gabbroids and lamprophyres of Samtskhe (South Georgia) dated around 9-8.5 Ma and teschenite intrusions of Guria dated at 7.5Ma. Petrological-geochemical and isotope-geochemical data indicate that the parental melts of the rocks of all studied Neogene plutonic bodies of the Lesser Caucasus were derived from a single mantle source. Its characteristics are close to those of a Common hypothetical reservoir, which is usually regarded as a source of oceanic and continental hot spot basalts (OIB) but shows some regional peculiarity. The role of crustal assimilation and crystallization differentiation in the genesis of the Miocene rocks of Guria was limited, which is related to the rapid ascent of deep melts to the surface (in a setting of local extension) without intense interaction with host sequences under the absence of consolidated continental lithosphere beneath this part of the Transcaucasus. The parental mantle-derived magmas of the Neogene gabbroids of Samtskhe were strongly contributed by upper crustal material, which caused a change in their isotope (⁸⁷Sr/⁸⁶Sr up to 0.70465, ?_Nd up to + 2.8) and geochemical characteristics relative to the regional mantle source. In addition, the crustal contamination of mantle basic melts during the late phases of the Samtskhe plutonic bodies formation led to their intense fractionation with precipitation of mainly olivine and pyroxene. The larger scale mantle-crustal interaction during formation of the Samtskhe intrusions was probably related to the fact that the upper lithosphere in this sector of the Transcaucasus contained large Paleozoic blocks, which were made up of granite-metamorphic complexes and prevented a rapid ascent of mantle melts to the surface. The rocks of these blocks were presumably assimilated by mantle magmas in the intermediate chambers at the upper crustal levels.  相似文献   

Experimental studies of the possibility of remote measuring of the velocity and direction of currents in the shallow water area of the Korean strait     

V. A. Akulichev  A. A. Golov  Yu. N. Morgunov  V. V. Bezotvetnykh  M. S. Lebedev  Kiseon Kim  Ju-Sam Park 《Doklady Earth Sciences》2014,457(1):893-895

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Major events in evolution of the Kazbek neovolcanic center,Greater Caucasus: Isotope-geochronological data     

V. A. Lebedev  A. V. Parfenov  G. T. Vashakidze  I. V. Chernyshev  Q. A. Gabarashvili 《Doklady Earth Sciences》2014,458(1):1092-1098

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.  相似文献   

Climate Change in the Hydrometeorological Parameters of the Black and Azov Seas (1980–2020)     

Ginzburg  A. I.  Kostianoy  A. G.  Serykh  I. V.  Lebedev  S. A. 《Oceanology》2021,61(6):745-756

Oceanology - To study the nature of climate change in the hydrometeorological parameters of the Black and Azov Seas—surface air temperature (SAT), sea surface temperature (SST), ice cover,...  相似文献   

Cobalt mineralization in the Altai–Sayan orogen: age and correlation with magmatism     

I.G. Tretiakova  A.S. Borisenko  V.I. Lebedev  G.G. Pavlova  V.A. Goverdovsky  A.V. Travin 《Russian Geology and Geophysics》2010,51(9):1078-1090

The paper discusses the spatiotemporal and genetic relationships of hydrothermal Co mineralization in the Altai–Sayan orogen with mafic, alkaline mafic, and granitoid magmatism on the basis of isotopic, geochemical, and geochronological investigations. Four stages of Co mineralization have been distinguished for this region: Early Devonian (D₁), Late Devonian–Early Carboniferous (D₃–C₁), Permo-Triassic (P₂–T), and Early Cretaceous (K₁). They correspond to periods of large-scale mafic magmatism. Isotopic (Pb, Sr, He) and geochemical studies have shown that Co mineralization is genetically related to mafic and granitoid magmatism. Also, these studies have confirmed that Co deposits are formed with the participation of mantle fluids and are related to chambers of mafic and alkaline mafic melts. Besides, it has been found that ore originated both from magmatic sources and host rocks. A pulsed facies endogenic zonation has been established for Co deposits, Co-bearing ore clusters, and zones with high-temperature Co–As and low-temperature Ni–Co–As mineralization. It has been first established that ores at hydrothermal Co deposits are rich in Pt and Pd.  相似文献   

A HED Laboratory Astrophysics Testbed Comes of Age: JET Deflection via Cross Winds     

A. Frank  E. G. Blackman  A. Cunningham  S. V. Lebedev  D. Ampleford  A. Ciardi  S. N. Bland  J. P. Chittenden  M. G. Haines 《Astrophysics and Space Science》2005,298(1-2):107-114

We present new data from High-Energy Density (HED) laboratory experiments designed to explore the interaction of a heavy hypersonic radiative jet with a cross wind. The jets are generated with the MAGPIE pulsed power machine where converging conical plasma flows are produced from a cylindrically symmetric array of inclined wires. Radiative hypersonic jets emerge from the convergence point. The cross wind is generated by ablation of a plastic foil via soft-X-rays from the plasma convergence region. Our experiments show that the jets are deflected by the action of the cross wind with the angle of deflection dependent on the proximity of the foil. Shocks within the jet beam are apparent in the data. Analysis of the data shows that the interaction of the jet and cross wind is collisional and therefore in the hydrodynamic regime. We consider the astrophysical relevance of these experiments applying published models of jet deflection developed for AGN and YSOs. We also present results of 3-D numerical simulations of jet deflection using a new astrophysical Adaptive Mesh Refinement code. These simulations show highly structured shocks occurring within the beam similar to what was observed in the experiments.  相似文献