11 results on '"V. N. Golubev"'
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2. Post-Ore Processes of Uranium Migration in the Sandstone-Hosted Type Deposits: 234U/238U, 238U/235U and U–Pb Systematics of Ores of the Namaru Deposit, Vitim District, Northern Transbaikalia
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N. N. Tarasov, V. N. Golubev, I. V. Chernyshev, B. T. Kochkin, G. V. Ochirova, and A. V. Chugaev
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geography ,geography.geographical_feature_category ,Drainage basin ,Geochemistry ,chemistry.chemical_element ,Geology ,Uranium ,Permafrost ,Mineral resource classification ,Basement (geology) ,Deposition (aerosol physics) ,chemistry ,Geochemistry and Petrology ,Economic Geology ,Leaching (metallurgy) ,Quaternary - Abstract
Abstract To assess the nature of the post-ore behaviour of uranium in the Namaru deposit (Khiagda ore field), U–Pb isotope systems and the isotopic composition of uranium (234U/238U and 238U/235U) were studied. The studied samples represent different ore zones of the deposit and were collected along cross-sections both vertically and horizontally. Wide variations in the isotopic composition of uranium and U–Pb isotopic age have been established. Deviations of the 234U/238U ratio from equilibrium values, which for some samples exceed 50%, along with significant variations in the isotopic age, indicate that permafrost layer, which covered the catchment areas of paleovalleys with meteoric oxygen-containing waters ca. 2.5 Ma ago, did not lead to preserving uranium ores at the deposit. Uranium migration took place during the Quaternary period. The effective combining the U–Pb dating and 234U/238U data in assessing the post-ore redistribution of uranium made it possible to recognize: removal of uranium from some zones of the ore body and its accompanying redeposition in others. Wide variations in the 238U/235U (137.484–137.851) ratios throughout the entire studied cross-sections can be explained by the different locations of samples relatively to the ore deposition front and change in redox conditions as this front advanced. Depletion of the light isotope 235U in the lower zone of the ore body may be associated with the influence of ascending carbonic waters established in the regional basement. The effect of such waters on uranium-bearing rocks causes predominant leaching of light 235U.
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- 2021
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3. The Northern Kazakhstan Uranium Province, Kokchetav Massif: U–Pb (ID-TIMS) and Rb–Sr Geochronology of Rocks of Ore-Hosting Volcanotectonic Depressions
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V. N. Golubev, E. B. Sal’nikova, K. N. Shatagin, and I. V. Chernyshev
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geography ,geography.geographical_feature_category ,Geochemistry ,chemistry.chemical_element ,Geology ,Massif ,Uranium ,010502 geochemistry & geophysics ,Geologic map ,01 natural sciences ,Mineral resource classification ,Devonian ,chemistry ,Geochemistry and Petrology ,Geochronology ,Economic Geology ,010503 geology ,Quartz ,Chemical composition ,0105 earth and related environmental sciences - Abstract
Geochronological studies have been conducted for ore-hosting rocks (quartz rhyolites, felsitic rhyolites, porphyry granites) of some U deposits of the Yakshi-Yangistau complex within the Balkashino ore center of the Northern Kazakhstan uranium province. According to geological maps of various scales, the rocks were traditionally ascribed to the Early–Middle Devonian (quartz and felsitic rhyolites) and Middle–Late Devonian (porphyry granites). The results of U–Pb, Rb–Sr, and K–Ar dating have shown that, according to the current version of the Geochronological Chart, the age of quartz rhyolites is Early–Late Silurian and that of felsitic rhyolites and porphyry granites is Late Silurian. The features of the chemical composition and different initial Sr isotopic composition of these rocks suggest that quartz rhyolites, felsitic rhyolites, and porphyry granites of the Yakshi-Yangistau complex are hardly comagmatic. They are characterized by different ages and formed from independent magmatic sources. Our data indicate the minimum possible age of the formation of primary U ores within the Balkashino ore center.
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- 2020
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4. Anomalous Lead Isotopic Composition of Galena and Age of Altered Uranium Minerals: a Case study of Chauli Deposits, Chatkal–Qurama District, Uzbekistan
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I. V. Chernyshev, V. N. Golubev, and A. V. Chugaev
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Radiogenic nuclide ,020209 energy ,Geochemistry ,chemistry.chemical_element ,Geology ,02 engineering and technology ,engineering.material ,Uranium ,010502 geochemistry & geophysics ,01 natural sciences ,Mineral resource classification ,Uranium ore ,chemistry.chemical_compound ,Uraninite ,chemistry ,Geochemistry and Petrology ,Galena ,Phanerozoic ,0202 electrical engineering, electronic engineering, information engineering ,engineering ,Carbonate ,Economic Geology ,0105 earth and related environmental sciences - Abstract
The enrichment of lead isotopic composition of nonuranium minerals, in the first place galena in 206Pb and 207Pb, as compared to common lead is a remarkable feature of uranium deposits. The study of such lead isotopic composition anomalous in 206Pb and 207Pb in uranium minerals provides an opportunity for not only identification of superimposed processes resulting in transformation of uranium ores during deposit history but also calculation of age of these processes under certain model assumptions. Galena from the Chauli deposit in the Chatkal–Qurama district, Uzbekistan, a typical representative of hydrothermal uranium deposits associated with domains of Phanerozoic continental volcanism, has been examined with the highprecision (±0.02%) MC-ICP-MS method. Twenty microsamples of galena were taken from polished sections. Six of them are galena hosted in carbonate adjacent to pitchblende spherulites or filling thin veinlets (approximately 60 μm) cutting pitchblende. Isotopically anomalous lead with 206Pb/204Pb and 207Pb/204Pb values reaching 20.462 and 15.743, respectively, has been found in these six microsamples in contrast to another fourteen in which the Pb–Pb characteristics are consistent with common lead. On the basis of these data and with account for the 292 ± 2 Ma age for the Chauli deposit, the age of epigenetic transformation of uranium ores of this deposit has been estimated. During this process, radiogenic lead partly lost from pitchblende was captured into galena. The obtained date is 170 Ma. In the Chatkal–Qurama district, these epigenetic processes are apparently caused by the interaction of uranium minerals with activated underground water under tectonic activity and relief transformation, which took place from the post-Permian (i.e., after the Chauli formation) to the Jurassic period.
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- 2017
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5. Polygenetic and polychronic uranium mineralization at deposits of the Khiagda ore field, Buryatia
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En. E. Asadulin, O. V. Andreeva, V. N. Golubev, N. N. Tarasov, and B. T. Kochkin
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geography ,geography.geographical_feature_category ,Field (physics) ,Geological evolution ,Geochemistry ,chemistry.chemical_element ,Geology ,Uranium ,010502 geochemistry & geophysics ,01 natural sciences ,Mineral resource classification ,Volcano ,chemistry ,Geochemistry and Petrology ,Uranium mineralization ,Economic Geology ,010503 geology ,0105 earth and related environmental sciences - Abstract
The unique combination of several exogenic processes augmenting uranium mineralization followed one another in time at deposits of the Khiagda ore field and gave rise to the formation of uranium resources exceptional for the paleovalley geologic and economic type. The specific geological evolution, volcanic activity, and regional climatic conditions taken together became the main cause of local occurrence of these deposits.
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- 2017
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6. The Schlema–Alberoda five-element uranium deposit, Germany: An example of self-organizing hydrothermal system
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B. P. Vlasov, O. F. Mironova, V. N. Golubev, and G. B. Naumov
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020209 energy ,Geochemistry ,Federal republic of germany ,Metamorphism ,Geology ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Mineral resource classification ,Hydrothermal circulation ,Tectonics ,Geochemistry and Petrology ,0202 electrical engineering, electronic engineering, information engineering ,Economic Geology ,0105 earth and related environmental sciences ,Uranium deposit - Abstract
As a result of integrating geological, mineralogical, and geochemical data on the unique Schlema–Alberoda five-element uranium deposit situated in Federal Republic of Germany and explored in detail down to a depth of 2 km, it has been shown that its formation for more than 100 Ma has been caused by combination of internal and external factors. The latter comprise favorable metallogenic specialization of the region, injection of intrusive bodies bearing the necessary stock of energy, and periodic pulses of tectonic reactivation. The internal factors of self-development involve evolutionary processes, which occur in host rocks at the consecutive stages of prograde and retrograde metamorphism giving rise to alteration of rocks in consistence with physical and chemical laws at variable temperature and degree of system opening.
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- 2017
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7. Fluorite as an Sm–Nd geochronometer of hydrothermal processes: Dating of mineralization hosted in the Strel’tsovka uranium ore field, eastern Baikal region
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A. P. Aleshin, Yu. O. Larionova, V. N. Golubev, I. V. Chernyshev, and Yu. V. Gol’tsman
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Isochron ,Mineralization (geology) ,Isochron dating ,Radiogenic nuclide ,020209 energy ,Geochemistry ,Mineralogy ,Geology ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Fluorite ,Hydrothermal circulation ,Uranium ore ,Uraninite ,Geochemistry and Petrology ,0202 electrical engineering, electronic engineering, information engineering ,Economic Geology ,0105 earth and related environmental sciences - Abstract
The possibility of using hydrothermal fluorite as an Sm–Nd geochronometer is based on the results of an REE pattern study of this mineral (Chernyshev et al., 1986). As a result of REE fractionation, in many cases, the Sm/Nd ratio achieves a multifold increase compared with its level in terrestrial rocks, and the radiogenic shift of the 143Nd/144Nd isotope ratio reaches 10–20 eNd units over a short time interval (as soon as tens of Ma). This is a necessary prerequisite for Sm–Nd isochron dating of fluorite. Zonal polychrome fluorite from a vein referred to the final stage of large-scale uranium mineralization at the Sterl’tsovka deposit in the ore field of the same name located in the eastern Transbaikal region has been dated using the 143Nd/144Nd method. To optimize isochron construction, local probes with high and contrasting Sm/Nd ratios have been sampled from the polished surfaces of two samples, taking into account the REE pattern of zonal fluorite. Sm–Nd isochron dating has been carried out separately for each sample. The 147Sm/144Nd и 143Nd/144Nd ratios vary within the intervals 0.5359–2.037 and 0.512799–0.514105, respectively. Two isochrons, each based on six fluorite probes, have been obtained with the following parameters, which coincide within 2σ uncertainty limits: (1) t = 134.8 ± 1.3 Ma, (143Nd/144Nd)0 = 0.512310 ± 13, MWSD = 0.43 and (2) t = 135.8 ± 1.6 Ma, (143Nd/144Nd)0 = 0.512318 ± 10, MWSD = 1.5. The mean age of fluorite based on two isochron datings is 135.3 ± 1 Ma. Comparison of this value with the most precise dating of pitchblende related to the ore stage in the Strel’tsovka ore field (135.5 ± 1 Ma) shows that four mineralization stages, distinguished by geological and mineralogical data, that were completed with the formation of polychrome fluorite veins 135.3 ± 1 Ma ago, represent a single and indivisible hydrothermal process whose duration does not exceed 1 Ma.
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- 2016
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8. U-Pb systems and U isotopic composition of the sandstone-hosted paleovalley Dybryn uranium deposit, Vitim uranium district, Russia
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A. V. Eremina, V. N. Golubev, Victoria V. Krupskaya, I. V. Chernyshev, A. N. Baranova, and A. V. Chugaev
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Terrigenous sediment ,Geochemistry ,chemistry.chemical_element ,Mineralogy ,Geology ,Uranium ,Mineral resource classification ,Isotopic composition ,Uranium ore ,Deposition (aerosol physics) ,chemistry ,Geochemistry and Petrology ,Economic Geology ,Uranium deposit - Abstract
The isotopic (U-Pb, 238U-235U, 234U-238U) and chemical study of whole-rock samples and finegrained fractions of rocks in a vertical section of the terrigenous sequence at the Dybryn uranium deposit in the Khiagda ore field shows that a wide U-Pb isotopic age range (26.9-6.5 Ma) is caused by oxidation and disturbance of the U-Pb isotopic system in combination with protracted uranium ore deposition. The oxidation of rocks resulted in the loss of uranium relative to lead and eventually to an overestimated 206Pb/238U age at sites with a low U content. The 238U/235U ratios in the studied samples are within the range of 137.74–137.88. Samples with a high uranium content are characterized by a decreasing 238U/235U ratio with a decrease in 207Pb/235U and 206Pb/238U ages. A nonequilibrium 234U/238U ratio in most studied samples furnishes evidence for young (
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- 2013
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9. Age of dispersed uranium mineralization in rocks of the framework of the Strel’tsovka uranium ore field and the Yamsky site, Eastern Transbaikal region
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V. N. Golubev
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Radiogenic nuclide ,Granitic rock ,Pluton ,Geochemistry ,chemistry.chemical_element ,Geology ,Uranium ,Mineral resource classification ,Uranium ore ,Uraninite ,chemistry ,Geochemistry and Petrology ,Uranium mineralization ,Economic Geology - Abstract
An isotopic geochronological study of dispersed uranium mineralization was performed in the granitic rocks of the Urtui pluton in the framework of the Strel’tsovka uranium ore field and in the Yamsky site of the Urov-Uryumkan granite-gneiss arch. Two stages of such mineralization—783 ± 26 Ma in the Urtui granitic pluton and 138.6 ± 2.3 Ma in the Yamsky site—have been established. The emplacement of granite pertaining to the Unda Complex disturbed the U-Pb isotopic system in uraninite from the Urtui granitic pluton and resulted in redeposition of uranium phase dated at 262 ± 34 Ma. The young, probably, recent process gave rise to the redistribution of radiogenic lead in the U-bearing phases developing after uraninite.
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- 2011
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10. The Strel’tsovka uranium district: Isotopic geochronological (U-Pb, Rb-Sr, Sm-Nd) characterization of granitoids and their place in the formation history of uranium deposits
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E. B. Sal’nikova, Yu. V. Golzman, E. D. Bairova, S. Z. Yakovleva, A. B. Kotov, I. V. Chernyshev, and V. N. Golubev
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Granitic rock ,Geochemistry ,chemistry.chemical_element ,Geology ,Uranium ,Mineral resource classification ,Hydrothermal circulation ,Uranium ore ,Basement (geology) ,chemistry ,Geochemistry and Petrology ,Uranium mineralization ,Economic Geology - Abstract
An isotopic geochronological study of Russia’s largest Strel’tsovka uranium district has been carried out. Polychronous granite generation, which determined the structure of the pre-Mesozoic basement, had important implications for the formation of volcanotectonic structural elements bearing economic uranium mineralization. The study of U-Pb, Rb-Sr, and Sm-Nd isotopic systems of whole-rock samples and minerals of granitic rocks allowed us to estimate the deportment of these systems in spatially conjugated granite-forming and hydrothermal processes differing in age and gave grounds for revising the age of granites pertaining to the Urulyungui Complex and refining the age of the Unda Complex.
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- 2010
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11. Deposition and remobilization of uranium in the North Baikal region: Evidence from the U-Pb isotopic systems of uranium ores
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L. V. Bylinskaya, L. B. Makar’ev, and V. N. Golubev
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Mineralization (geology) ,Isotope ,Geochemistry ,chemistry.chemical_element ,Mineralogy ,Geology ,Uranium ,Isotope dilution ,Mass spectrometry ,Mineral resource classification ,Devonian ,Uraninite ,chemistry ,Geochemistry and Petrology ,Economic Geology - Abstract
Based on the study of local volumes of minerals, including their microsampling and subsequent analysis of Pb/Pb and U/Pb isotope ratios with the classic methods of isotopic dilution and thermoionization mass spectrometry (TIMS), U-Pb and Pb-Pb isotopic datings of minerals were carried out in uranium ores from deposits in the Akitkan and Nechera-Nichatka ore districts (North Baikal region). Reliable evidence in favor of the Middle Devonian (384 ± 8 Ma) remobilization of Paleoproterozoic primary uranium concentrations and the redeposition of uranium as pitchblende 2 has been obtained for the first time for ores of the Akitkan district. The Paleoproterozoic (1832 ± 13 Ma) age of uraninite mineralization and the timing of the latest (377 ± 5 Ma) transformation of uranium ores at the Chepok deposit (Nechera-Nichatka district) are substantiated.
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- 2008
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