Geochronology of Quaternary volcanism of the Krestovyi Pass Region, Kazbek Neovolcanic Area, Greater Caucasus     

V. A. Lebedev  I. V. Chernyshev  A. V. Chugaev  G. T. Vashakidze 《Doklady Earth Sciences》2007,413(2):272-276

  相似文献   

Geochronology and genesis of subalkaline basaltic lava rivers at the Dzhavakheti highland,lesser Caucasus: K-Ar and Sr-Nd isotopic data     

V. A. Lebedev  S. N. Bubnov  I. V. Chernyshev  A. V. Chugaev  O. Z. Dudauri  G. T. Vashakidze 《Geochemistry International》2007,45(3):211-225

The paper reports newly obtained K-Ar isotopic-geochronological data on the age of three lava flows (Khrami, Mashavera, and Kura), which begin at the Dzhavakheti volcanic highland in southern Georgia. All of the dated rocks, including those from the Kura Flow, which was previously considered as the Pleistocene, are demonstrated to have a Pliocene age. The lavas of the longest Khrami Flow were erupted at 3.25–3.10 Ma, and those of the Kura and Mashavera Flows at 2.20–2.05 Ma, a fact testifying to two pulses of volcanic activity at the Dzhavakheti Highland. The petrogeochemical and isotopic characteristics of the rocks (⁸⁷Sr/⁸⁶Sr = 0.7039–0.7042; ∈_Nd = 3.4–5.1) indicate that they are subalkaline within-plate basalts formed by the fractional crystallization of a basic mantle melt with the usually discontinuous selective or rarely continuous contamination with material that was not in geochemical equilibrium with the melt. The volcanics of the Khrami Flow are characterized by the less radiogenic Sr isotopic composition and the highest ∈_Nd values, while the younger rocks of the Mashavera and Kura Flows have similar and more “crustal” isotopic signatures. The ⁸⁷Sr/⁸⁶Sr ratios of the Dzhavakheti subalkaline basalts are close to the initial Sr isotopic ratios of the Quaternary and Middle Pliocene dacite lavas from the same territory. Considered together with petrogeochemical and geological data, this suggests that all young rocks in Southern Georgia were produced in similar tectonic and geodynamic environments.  相似文献   

Geothermal characteristics of the crimean peninsula and some areas of the eastern carpathians     

T. S. Lebedev  R. I. Kutas  V. V. Gordiyenko 《Bulletin of Volcanology》1969,33(1):190-203

  相似文献   

Geochronology of Neogene-Quaternary volcanism of the Geghama Highland (Lesser Caucasus,Armenia)     

E. V. Arutyunyan  V. A. Lebedev  I. V. Chernyshev  A. K. Sagatelyan 《Doklady Earth Sciences》2007,416(1):1042-1046

  相似文献   

Geochronology of Quaternary volcanism of the Krestovyi Pass Region,Kazbek Neovolcanic Area,Greater Caucasus     

V. A. Lebedev  I. V. Chernyshev  A. V. Chugaev  G. T. Vashakidze 《Doklady Earth Sciences》2007,413(1):272-276

  相似文献   

Jet Deflection by a Quasi-Steady-State Side Wind in the Laboratory     

David J. Ampleford  Andrea Ciardi  Sergey V. Lebedev  Simon N. Bland  Simon C. Bott  Jeremy P. Chittenden  Gareth N. Hall  Adam Frank  Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34

We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium.  相似文献   

Geochronology of eruptions and parental magma sources of Elbrus volcano,the Greater Caucasus: K-Ar and Sr-Nd-Pb isotope data     

V. A. Lebedev  I. V. Chernyshev  A. V. Chugaev  Yu. V. Gol’tsman  E. D. Bairova 《Geochemistry International》2010,48(1):41-67

Complex geochronological and isotope-geochemical studies showed that the Late Quaternary Elbrus volcano (Greater Caucasus) experienced long (approximately 200 ka) discrete evolution, with protracted periods of igneous quiescence (approximately 50 ka) between large-scale eruptions. The volcanic activity of Elbrus is subdivided into three phases: MiddleNeopleistocene (225–170 ka), Late Neopleistocene (110–70 ka), and Late Neopleistocene-Holocene (less than 35 ka). Petrogeochemical and isotope (Sr-Nd-Pb) signatures of Elbrus lavas point to their mantle-crustal origin. It was shown that hybrid parental magmas of the volcano were formed due to mixing and/or contamination of deep-seated mantle melts by Paleozoic upper crustal material of the Greater Caucasus. Mantle reservoir that participated in the genesis of Elbrus lavas as well as most other Neogene-Quaternary magmatic rocks of Caucasus was represented by the lower mantle “Caucasus” source. Primary melts generated by this source in composition corresponded to K-Na subalkali basalts with the following isotopic characteristics: ⁸⁷Sr/⁸⁶Sr = 0.7041 ± 0.0001, ƒ_Nd = +4.1 ± 0.2, ¹⁴⁷Sm/¹⁴⁴Nd = 0.105–0.114, ²⁰⁶Pb/²⁰⁴Pb = 18.72, ²⁰⁷Pb/²⁰⁴Pb = 15.62, and ²⁰⁸Pb/²⁰⁴Pb = 38.78. The temporal evolution of isotope characteristics for lavas of Elbrus volcano is well described by a Sr-Nd mixing hyperbole between “Caucasus” source and estimated average composition of the Paleozoic upper crust of the Greater Caucasus. It was shown that, with time, the proportions of mantle material in the parental magmas of Elbrus gently increased: from ∼60% at the Middle-Neopleistocene phase of activity to ∼80% at the Late Neopleistocene-Holocene phase, which indicates an increase of the activity of deep-seated source at decreasing input of crustal melts or contamination with time. Unraveled evolution of the volcano with discrete eruption events, lacking signs of cessation of the Late Neopleistocene-Holocene phase, increasing contribution of deep-seated mantle source in the genesis of Elbrus lavas with time as deduced from isotope-geochemical data, as well as numerous geophysical and geological evidence indicate that Elbrus is a potentially active volcano and its eruptions may be resumed. Possible scenarios were proposed for evolution of the volcano, if its eruptive activity were to continue.  相似文献   

Erratum: Geochronology of Late Cenozoic volcanism in the area of Lake Van,Turkey: An example of developmental dynamics for magmatic processes [Doklady earth sciences, 433(2), pp. 1031–1037]     

Lebedev  V. A.  Sharkov  E. V.  Keskin  M.  Oyan  V. 《Doklady Earth Sciences》2010,435(1):1548-1554

An isotope-geochronological study has been performed to examine the products of Late Cenozoic collision volcanism on the northern coast of Lake Van, Turkey. We obtained 45 new K—Ar dates, based on which the principal time characteristics of volcanic activity in the region have been determined. Volcanic activity in the northern coast of Lake Van has lasted ∼15 myr; it has had an expressed discrete nature, when periods of intense volcanic activity alternated with long-lasting pose periods. Four stages of Neogene—Quaternary volcanism have been identified: Middle Miocene (15.0—13.5 Ma), Late Miocene (10—9 Ma), Pliocene (5.8—3.7 Ma), and Quaternary (1.0—0.4 Ma). The average duration of the stages was 1—2 myr; the stages were separated from each other with periods of inactivity of approximately equal lengths (∼3 myr). For each of the Pliocene and Quaternary stages, three additional phases of volcanism have been identified, which were separated from each other with short time intervals (a few hundred thousand years). The last burst of volcanic activity in the study area occurred ∼400 ka; similar to Quaternary volcanism in general, it was not characterized by a high intensity. An important result of the studies performed was to confirm the existence of a separate Middle Miocene stage of collision volcanism for the Caucasian—Anatolian Segment of the Alpine Fold Belt. New geochronological data generated presented in this paper indicate that Neogene—Quaternary volcanism in this portion of the belt started much earlier (∼15 Ma) than assumed by the majority of the previous researchers.  相似文献   

Significance of sea water supercooling and intrawater ice generation for the formation of water mass and ice cover in the East Siberian and Chukchi seas     

G. A. Lebedev  V. I. Fedotov  N. V. Cherepanov 《Russian Meteorology and Hydrology》2014,39(2):93-99

  相似文献   

Middle Pleistocene warming phase based on the deposits of a buried oyster reef,Southern Lesser Kuril Islands     

N. G. Razjigaeva  L. A. Ganzey  T. A. Grebennikova  N. I. Belyanina  A. M. Lebedev  F. E. Maksimov  V. Yu. Kuznetsov 《Doklady Earth Sciences》2014,455(2):376-382

  相似文献