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Vol. 18 (2015 year), No. 2
Kaulina T. V., Bayanova T. B., Talat Ahmad, Lyalina L. M., Mishra M. K., Nitkina E. A., Elizarov D. V., Serov P. A.
Evolution of the Central Indian tectonic zone:Geochemical and isotope-geochronological data
In the framework of the Russian-Indian joint research projects geochemical and geochronological study of granitoid rocks across the Central Indian Tectonic Zone has been carried out. Geochronological data suggest that the Central Indian Tectonic Zone is composed primarily of Proterozoic rocks, formed as a result of several stages of granitoid magmatism: at 2.43, 2.34-2.31, 1.73-1.72 and 1.53-1.51 Ga. Metamorphic transformations reflected by Sm–Nd and Rb–Sr systems of rocks and minerals occurred 1.37-1.1 Ga ago that allows comparing the final processes in the Central Indian Tectonic Zone with the Grenville orogeny and it can be used for the reconstruction of Rodinia
(in Russian, стр.10, fig. 3, tables. 1, ref 13, Adobe PDF, Adobe PDF 0 Kb)
Vol. 22 (2019 year), No. 1, DOI: 10.21443/1560-9278-2019-22-1
Terekhov E. N., Morozov Yu. A., Smolkin V. F., Bayanova T. B., Serov P. A., Shcherbakova T. F., Smulskaya A. I.
Features of dike magmatism in the Northern frame of the Pechenga structure
A comprehensive study of Paleoproterozoic dike complexes within North-Western part of the Kola region has been carried out. The research allows establish stages of their formation, correlate with thickness of volcanites and reconstruct the geodynamic conditions of introduction. The most common dikes are composed of quartz dolerites with U-Pb age 2304 ± 1 Ma, εNd = –1.12 and model Sm-Nd protolite age – 2838 Ma. Dikes from the Ambarnaya Bay area correlate to dike swarm of the village Liinakhamari. Rocks of both swarms are correlated with volcanogenic formations of andesibasalt composition, the lower part of Pechenga structure section. Small fluctuations MgO (4–7 wt.%), low Cr (10–50 ppm) and moderate Y, Zr, REE, weakly fractionated HREE with minor negative Eu anomaly and (La/Yb)n = 5.1–5.8 are typical for dolerites. Rocks are enriched by Rb, Ba, K, depleted by Nb, Ti, and have low Sr/Y = 11–13. Dikes of quartz dolerites break plagiogranites and granites of the Archean foundation. U-Pb age of plagiogranites is 2722 ± 4 Ma. Age of granites is younger – 2418 ± 8 Ma. Plagiogranite according to Sm-Nd analysis of its gross sample has εNd = +3.77, which is close to the values of depleted mantle and indicates the origin of the rock from depleted mantle source. Granite of xenoliths dikes of quartz dolerites is characterized by εNd = –0.36. This indicates formation of rocks from a source more enriched than CHUR reservoir. The model Sm-Nd age of the protolite is 2744 Ma. These data confirm the initiation of rifting of Paleoproterozoic Pechenga-Varzugskaya belt in the continental crust. The synchronous introduction of dike swarms of quartz dolerites with the eruption of andesibasalt volcanites is determined by their structural confinement in the regional part of the "dying" sumian plume and to region of dynamic influence of regional shear zones
(in Russian, стр.16, fig. 8, tables. 5, ref 24, Adobe PDF, Adobe PDF 0 Kb)
Vol. 24 (2021 year), No. 1, DOI: 10.21443/1560-9278-2021-24-1
Kalinin A. A., Kaulina T. V., Serov P. A.
Comparison of isotope data obtained with Sm-Nd and Re-Os methods for minerals and rocks from the Ozernoe ore occurrence, Salla-Kuolajarvi belt
Sm-Nd isochrone, drawn for rock-forming and sulfide minerals from the Ozernoe ore occurrence, indicates albitite age of 1,759 ± 11 Ma. It shows synchronous formation of albitite and sulfide mineralization, and fully corresponds to the earlier defined age of rutile in albitite (1,757 ± 7 Ma U-Pb, n = 3, MSWD = 0.2), and Rb-Sr isochrone age 1,754 ± 39 Ma for biotite, apatite, albite, and WR. Recently published Re-Os ages of molybdenite 1,872 ± 23 Ma and chalcopyrite 1,891 ± 230 Ma indicate more ancient age of sulfide mineralization. These figures are in conflict with the age of rock-forming minerals, defined with Sm-Nd and Rb-Sr methods. The possibility of use of molybdenite from the Salla-Kuolajarvi belt for rock dating has been considered, and low reliability of Re-Os method for it has been shown. The reasons are the following: 1) extremely uneven distribution of Re in molybdenite, where Re content varies 1 wt.% even within one and the same grain, and 2) openness of the Re-Os system after molybdenite crystallization, Re is mobylized and partly removed from the mineral in the zone of hypergenesis. Removal of Re from molybdenite promotes erroneous ancient age of the molybdenite. According to the equations of radioactive decay, the age would be 110–130 Ma bigger if 5–6 % of Re is taken away. The conclusion is that molybdenite must be studied in detail, proved to be homogenous and unaltered, before it is used for Re-Os dating. In the other case the results will be not reliable.
(in Russian, стр.8, fig. 2, tables. 1, ref 32, AdobePDF, AdobePDF 0 Kb)
Vol. 25 (2022 year), No. 1, DOI: 10.21443/1560-9278-2022-25-1
Nitkina E. A., Serov P. A.
Zircon morphology and isotope U-Pb and Sm-Nd dating the rocks of the Kanozero alkaline granite massif (the Kola region)
The U-Pb dating zircon and Sm-Nd dating the whole rock and secondary minerals from the Kanozero massif of alkaline granites of the Kola region (the Fennoscandian shield) have been carried out. The age of alkaline granites of the Kanozero massif by zircon is 2667 ± 36 Ma, aplite-like alkaline granites – 2301 ± 13 Ma and blastomylonites – 2264 ± 12 Ma. The crystallization temperature of zircon has been estimated from the crystal habit. According to the zircon morphology of alkaline granites and blastomylonites the conditions during the crystallization process of the Kanozero massif have been established as long-term cooling high-temperature volatile- and alkali-rich crustal-mantle melts. The mineral Sm-Nd isochron by whole rock and by secondary minerals – biotite and titanite – has an age of 1921 ± 53 Ma interpreted as the time of regional Svecofene metamorphism. Based on the obtained isotopic data it can be noted that the rocks of the Kanozero massif of alkaline granites have similar features of formation and transformation with alkaline granites of the Keivsky terrane.
(in Russian, стр.11, fig. 8, tables. 3, ref 24, AdobePDF, AdobePDF 0 Kb)