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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. 21 (2018 year), No. 1, DOI: 10.21443/1560-9278-2018-21-1

Nitkina E. A., Bayanova T. B.
Isotope-geochronological study of Ingozero massive (the Kola Peninsula)

The Ingozero massive composed of Archeaen gneisses and granitoids is situated in the north-eastern part of the Belomorian mobile belt. The Ingozero massive petrochemical and geochemical characteristics are similar to those of tonalite-trondhjemite-granodiorite (TTG) complexes established on other Archean shields. High concentrations of Na, Ca, and low of K characterize the gneisses of the Ingozero massif and the samples points lie on the tonalite and trondhjemite fields on the Ab-An-Or diagram. The high content of light rare earth elements and the absence of Eu anomalies indicate the origin of rocks from enriched sources without the essential role of fractional crystallization. The isotope U-Pb single zircon grains dating of the biotite gneisses yielded the oldest age for the Ingozero gneisses magmatic protolith at 3 149 ± 46 Ma. Model Sm-Nd ages have shown the formation of the gneisses protolith initial melt occurred at 3.1–2.8 Ga. The ages of metamorphic processes were determined by isotope U-Pb dating (ID TIMS): biotite gneisses – 2 697 ± 9 Ma; amphibole-biotite gneisses – 2 725 ± 2 and 2667 ± 7 Ma; and biotite-amphibole gneisses – 2 727 ± 5 Ma. The ages for granitoids, which cut the deformed gneisses are 2 615 ± 8 Ma and 2 549 ± 30 Ma for plagiogranites and pegmatoid veins in gneisses respectively

(in Russian, стр.9, fig. 5, tables. 4, ref 21, 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)