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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. 20 (2017 year), No. 1, DOI: 10.21443/1560-9278-2017-20-1/1
Kaulina T. V., Nerovich L. I., Bocharov V. N., Lyalina L. M., Il'chenko V. L., Kunakkuzin E. L., Kasatkin I. A.
Raman spectra of impact zircons in the Jarva-varaka layered massif
(the Monchegorsk ore region, the Kola Peninsula)
Zircon crystals from granophyre norites of the Jarva-varaka massif of the Monchegorsk ore region (the Kola Peninsula) have been studied by means of back-scattered electron (BSE) imaging and Raman spectroscopy. The Jarva-varaka massif according to geological and geochemical data has been compared with the Sudbury structure, for which an impact origin is assumed. Zircon study is stipulated by zircon ability to keep signs of shock metamorphism even under granulite-facies conditions, thus it can be used for identification of ancient impact structures. BSE images reveal complicated internal texture – darker central domains (cores) and light rims without texture. Mineral inclusions in zircon are represented by sillimanite and plagioclase which indicates that the studied zircon grains were inherited from the host aluminous gneisses. Zircon crystals show variation of Raman spectra from the core of crystals with typical zircon Raman pattern to complete absence of spectral bands in the marginal parts and rims. Mineral inclusions in zircon rims also have no Raman spectra. Such patterns may be associated with the transformation of crystalline zircon (and mineral inclusions in it) to diaplectic glass under the influence of shock metamorphism, core domains were screened by rims and thus preserved their structure. The received data suggest the participation of the meteorite impact in the formation of the Jarva-varaka massif that requires further investigation.
(in Russian, стр.11, fig. 4, tables. 0, ref 28, Adobe PDF, Adobe PDF 0 Kb)
Vol. 22 (2019 year), No. 1, DOI: 10.21443/1560-9278-2019-22-1
Kaulina T. V., Lyalina L. M., Il'chenko V. L.
Sequence of REE-Th-U minerals in the Litsa uranium ore area (the Kola Region)
Mineralogical and petrographic study of REE-Th-U mineralization in rocks of the Litsa uranium ore area has been carried out to detail the sequence of formation of rare-earth, uranium and thorium minerals in rocks. The study has been aimed to Dikoe ore occurrence with the earliest in the area REE-Th-U mineralization described by previous workers. Rocks and minerals have been studied by means of optical and electron microscopy, as well as microprobe methods, this has made it possible to identify the relationship of minerals and the sequence of their crystallization. In monzodiorite veins and host biotite gneisses are found accessory minerals represented by monazite-(Ce), uraninite, zircon, apatite, and thorite, which are in close association with each other, but are formed at different stages of formation and transformation of the host rocks. Monazite-(Ce) with high thorium content (9–10 %) in association with apatite grows at the magmatic stage of monzodiorite crystallization both in the veins themselves and after the fine-grained mass of minerals in the biotite plates of the host gneisses. Magmatic zircon with elevated content of thorium and uranium crystallizes in veins together with monazite and apatite. The formation of uraninite, containing impurities of sulfur, yttrium and calcium, and associated with areas of granulation of plagioclase, occurs as a result of hydrothermal-metasomatic processes in veins simultaneously with the formation of textureless zircon rims with high calcium, iron, and hafnium content in the host gneisses. The development of galgenbergite and anglesite rims around uraninite grains reflects the next superimposed hydrothermal processes
(in Russian, стр.11, fig. 6, tables. 3, ref 12, Adobe PDF, Adobe PDF 0 Kb)
Vol. 23 (2020 year), No. 1, DOI: 10.21443/1560-9278-2020-23-1
Nitkina E. A., Kaulina T. V. , Kozlov N. E.
The ages and rock mineral composition of the Pechenga eastern frame, the Kola region
The research and dating of rocks in the area of the Central Kola block (the Kola Peninsula) is due to the need to develop the Lyceum uranium ore area, the most promising for uranium mining in the Kola region, located in close proximity to the study area and composed of similar gneisses from the Kola series. Within the Central Kola block, Archean complexes are represented by granite-gneisses and migmatites with relicts of biotite-plagioclase, biotite-amphibole-plagioclase gneisses, amphibolites, garnet-biotite-plagioclase and aluminous gneisses containing interlayers of ferruginous quartzite (quartz metasomatites) of various capacities. The rocks are repeatedly metamorphosed in conditions from high-temperature steps of the amphibolite facies to the granulite facies. Geological and geochronological methods have established the sequence of geological processes manifested in the rocks of the Kola series of the northwest framing of the Pechenga structure. The results of U-Pb dating are determined by zircon grains of the following genesis: metamorphic – in gneiss; magmatic and metamorphic – in metagabbro; metamorphic and metasomatic – in quartz metasomatite. The data obtained have made it possible to establish the age sequence of geological processes: 2.8 Ga – the time of metamorphism of garnet-biotite gneisses; 2,722 ? 9 Ma – crystallization of granodiorites; 2,636 ± 41 Ma – the formation of aplitic granites; 2,620 ? 16 Ma – the emplacement of pegmatites; the age of aplitic granites and pegmatites marks the final stages of the Archean evolution of the region; 2,587 ± 5 Ma – the emplacement of gabbroids, 2,522–2,503 Ma – the period of the thermal process associated with the formation of quartz metasomatites during the metamorphism of gabbro and garnet-biotite gneisses; 2,507 ± 7 Ma – metamorphism, schist and budding of gabbroids.
(in Russian, стр.10, fig. 4, tables. 1, ref 31, AdobePDF, AdobePDF 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)