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Vol. 19 (2016 year), No. 1, DOI: 10.21443/1560-9278-2016-1/1

Kudryashov N. M., Skublov S. G., Kalinin A. A., Lyalina L. M.
Mineralogical and geochemical characteristics of zircon from diorite porphyry dyke in Sergozerskoe gold occurrence (the Strel'ninsky greenstone belt, Kola region)

Mineralogical and geochemical investigation of zircon from diorite porphyry from Sergozerskoe occurrence has been carried out. Study of morphology and inner structure of zircon crystals in back scattered electron rays as well as assaying for content and distribution of Rare Earth Elements in mineral grains have given important information about conditions of crystallization and following metasomatic alteration of zircon. Zircon characteristics show that it crystallized in a melt, enriched in fluid phase. Fluid influence lasted after zircon crystallization, this reflected in uneven composition of the mineral and in configuration of REE spectra, typical for metasomatic zircon. Similar zircon characteristics have been noted in zircons from other gold occurrences in greenstone belts in the Kola region

(in Russian, стр.0, fig. 0, tables. 0, ref 0, Adobe PDF, Adobe PDF 0 Kb)

Vol. 24 (2021 year), No. 2, DOI: 10.21443/1560-9278-2021-24-2

Skublov S. G., Mamykina M. E., Rizvanova N. G.
U-Pb age and trace elements composition of titanite from granites of Belokurikhinsky massif, Gorny Altai

As a result of isotope-geochemical study, the age data (U-Pb method, ID-TIMS) of titanite from the first phase granites of the Belokurikhinsky granite massif, Gorny Altai, were obtained for the first time. The concordant value of the titanite age of 255 ± 2 Ma coincides within the margin of error with the previously published results of dating micas from granites of the second and third phases of the Belokurikha massif by the Ar-Ar method (250 ± 3 Ma). At the same time, the results of dating differ significantly from the previously published age values for the granites of the Belokurikha massif (232 ± 5 Ma, U-Pb method for the monofraction of zircon grains; 245 ± 8 Ma, Rb-Sr method for the whole rocks). Therefore, there is every reason to narrow the time interval of the formation of the Belokurikha granite massif to 255–250 Ma. The study of the trace element composition of titanite by SIMS demonstrated their zonal structure. The central part of the titanite grain differs from the rim by a noticeably higher content of REE, Cr, Y, and Nb. The content of V, Zr and Ba decreases to a lesser extent towards the rim, the content of Sr and U remains constant. At the same time, the REE distribution spectra in the central and rim parts are conformal to each other, having a convex spectrum for LREE and a concave one for HREE. Titanite is characterized by a negative Eu-anomaly, the depth of which decreases to the rim of the grain. A negative Eu-anomaly indicates the co-crystallization of titanite and plagioclase. The REE distribution spectra in titanite from the Belokurikha massif correspond to the characteristics of a typical magmatic titanite from granitoids and differ significantly from the distribution spectra in metamorphic titanite.

(in Russian, стр.9, fig. 4, tables. 3, ref 27, AdobePDF, AdobePDF 0 Kb)

Vol. 28 (2025 year), No. 1, DOI: 10.21443/1560-9278-2025-28-1

Rogova I. V., Skublov S. G., Berezin A. V., Petrov D. A.
Geochemical characterization of Gubanovskaya intrusion of rapakivi granites (Wiborg massif)

The paper presents new data on geology and composition of rapakivi granites of Gubanovskaya intrusion (Wiborg massif). Petrographic and geochemical characteristics of rapakivi granites of the second (ovoid) and third (trachytoid) phases of intrusion, as well as granites from the phase contact zone have been considered. Data on rock composition were obtained by XRF and ICP-MS methods. Ovoid granites are characterized by increased amounts of alumina and iron and calcium oxides, as well as high concentrations of barium and light rare earths, compared to trachytoid granites and rocks of the contact zone. Trachytoid granites are characterized by increased silica content compared to the granites of the second phase, and reduced barium and strontium values, which indicate the evolution of magma towards differentiation, typical for the late phases of intrusions of rapakivi granites. The contact zone rocks show the highest silica and REE contents. Anomalously high LREE content is comparable to rare-metal pegmatites of Olympic Dam, which may indicate the possibility of mineralization detection in them. The results of the study of rocks have shown that all studied granites by their geochemical characteristics belong to intraplate granites of A-type, namely A2-type rocks of crustal or mantle-crustal origin, and belong to calcareous-alkaline and shoshonite series.

(in Russian, стр.12, fig. 3, tables. 2, ref 26, AdobePDF, AdobePDF 0 Kb)