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Shchapova Yu. V. Votyakov S. L. Ivanov V. Yu. Pustovarov V. A. 《Geology of Ore Deposits》2010,52(7):679-687
The luminescence properties of two single zircon crystals from kimberlite of Yakutia have been studied, excited by the DORIS
HASYLAB synchrotron, Germany, within energy range from the visible to the soft X-ray region (5–25, 50–200, and 500–620 eV)
at temperatures of 300 and 10 K. The luminescence spectra in the range of 2.5 to 6.0 eV and excitation spectra of the main
bands have been examined, the physical nature of the luminescence centers has been discussed, and the luminescence properties
of a crystal containing growth (radiation) structural defects and a crystal with the same impurities but annealed in air at
1200°C are compared. The zoned structure of the mineral has been considered and the value of the energy gap (E
g) in the mineral has been estimated at 7.1 eV. Two groups of luminescence bands caused by impurities of intrinsic (growth,
radiation) nature (E
max = 2.1, 2.7–2.8, and 3.2–3.3 eV) and matrix luminescence (E
max = 4.4−4.7 and 5.4 eV) probably with the participation of excitons were distinguished on the basis of selective excitation
of zircon with different synchrotron energies relative to the gap value (E
excit < E
g, E
excit ∼ E
g, and E
excit ≫ E
g). The short-lived component with a response time of 4 ns has been revealed in the afterglow of zircon in the region of 5.4
eV. 相似文献
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S. L. Votyakov V. V. Khiller Yu. V. Shchapova Yu. V. Erokhin 《Geology of Ore Deposits》2013,55(7):515-524
To develop further chemical microprobe timing of U-Th-bearing minerals on the basis of upgraded measurement techniques and special age calculation, uraninite, thorite, thorianite, coffinite, monazite from several localities in the Urals and Siberia have been dated. The samples were taken from granitic rocks of the Pervomaisky pluton in the Central Urals; the pre-Jurassic basement of western Siberia and Yamal Peninsula; carbonatite-like dolomite from the Karabash ultramafic massif in the Southern Urals; granitic pegmatites of the Lipovsky vein field; and quartz-sulfide veins of the Pyshma-Klyuchevsky Cu-Co-Au deposit in the Central Urals. Scrutiny of the composition and chemical heterogeneity of mineral grains is a necessary stage of chemical dating aimed at the estimation of the degree of closeness of the U-Th-Pb system and unbiased screening of analytical data. The condition (Si + Ca)/(U + Th + Pb + S) ～ 1 was used as evidence for significant secondary alteration of monazite; the negative correlation between Pb and Th or U +Th in uranitite was used for the same purpose. The positive correlation between Pb and U, along with low concentrations of Ca, Si, and Fe admixtures, implies that the stoichiometric composition of thorite is close to 100%. The reliability and accuracy of the chemical dating of minerals with high contents of radioactive elements can be enhanced by using bimineralic or multimineralic isochrons, e.g., monazite-uraninite, uraninite-coffinite, etc. The results obtained have been compared with the available isotopic ages of the studied minerals; the compared data are satisfactorily consistent. 相似文献
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Features of metamict zircons based on their micrographs and the data of electron microprobe analysis
S. L. Votyakov D. A. Zamyatin Yu. V. Shchapova A. V. Porotnikov A. A. Krasnobaev 《Doklady Earth Sciences》2014,457(1):882-886
A new quantitative approach on the basis of joint probability distribution (JPD) analysis of BSE- and CL-images is proposed for studies of the zoning of polygenic (polychronous) grains of zircon. It was shown for the example of zircon of the Mugodzhar metamorphic rocks (South Ural) that a series of zones might be distinguished in the grains of high chemical (structural) heterogeneity. Zones Ia and Ib belong to the fragments of crystalline and radiation-damaged zircon, respectively. Zone II corresponds to the primarily disordered areas (the “genetically metamict” zones) of high concentrations of the impurities of Y, P, REE, U, Hf, etc. The Ia-Ic trend is related to the process of autoradiation metamictization. Based on the data on oxygen content, the declinations of zircon composition from the stoichiometry and the hydration effects were considered. 相似文献
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To develop chemical microprobe timing of U-Th-bearing minerals, monazite grains from several localities in the Ural and Siberia have been dated using upgraded measurement techniques and age calculation based on original software. The samples were taken from pegmatites of the Ilmeny Mountains and the Ilmeny-Vishnevy Mountains Complex in the South Urals; pegmatites from the Adui granitic pluton and its framework in the Central Urals; gneisses and granulites of the Taratash Complex in the South Urals; and felsic gneisses from the Transangara region of the Yenisei Ridge. Scrutiny of the composition, heterogeneity, and chemical substitution of U and Th ions is a necessary stage of chemical dating aimed at estimating the degree of closeness of the U-Th-Pb system and unbiased screening of analytical data. The results obtained have been compared with the known isotopic ages of the studied minerals; the compared data are satisfactorily consistent. 相似文献
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Zamyatin Dmitry A. Shchapova Yuliya V. Votyakov Sergey L. Nasdala Lutz Lenz Christoph 《Mineralogy and Petrology》2017,111(4):475-497
Mineralogy and Petrology - The U-Th-Pb isotope system in the accessory mineral zircon may be disturbed, as for instance by the secondary loss of radiogenic lead. The recognition of such alteration... 相似文献
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