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Vol. 18 (2015 year), No. 2
Nikiforov S. L., Koshel S. M., Sorokhtin N. O., Kozlov N. E.
Seabed digital elevation models and some possibilities of their morphometric analysis
Seabed bathymetry is an important component of marine geology and geomorphology activity, so as cartography and paleogeography, geoecology and hydroacoustics and other applied areas of research also. General seabed digital elevation model (DEM) could be the basement in the definition of "key" shelf areas for further detailed study, including sound profiling. All of them are required at the stage of industrial planning, construction and exploration, definition of geo-hazard, for the monitoring activity and also required to repel potential threats, including natural ones, etc. Developed methods are the most adequate approach for optimization of material costs, considering the large amount, sometimes huge, costs of marine field research. Simulation of seabed relief within large areas is always connected with the limit of hydrographic survey data. From the other hand, detailed knowledge of the bottom topography for software-based automatic processing is not expected in the near future and is not possible now due to technical reasons. Thus, all available geological and morphological information should be used. Our technique is based on the analysis and digitizing of the navigation charts of different scale and drawing manually additional isobaths under developed classification of seabed relief. Using the DEM it is possible to determine some series of morphometric parameters based on calculating the derivative grid models
(in Russian, стр.8, fig. 6, tables. 0, ref 9, Adobe PDF, Adobe PDF 0 Kb)
Vol. 19 (2016 year), No. 1, DOI: 10.21443/1560-9278-2016-1/1
Sorokhtin N. O., Nikiforov S. L., Koshel S. M., Kozlov N. E.
Geodynamic evolution and orphostructural analysis of the Western sector of the Russian Arctic shelf
The paper considers issues of the Barents Sea shelf geodynamic evolution and influence of basement geologic structural processes on seabed morphology in their interaction. The obtained data have made possible to assume that the Norwegian-Mezenskaya rift system, Voronin graben, St. Anne and Victoria grabens were formed at the expense of the lithosphere stretching processes, but the Vostochno-Barentsevomorskaya basin and Medvezinsko-Edzinskaya area of depressions developed on the initial stage of lithosphere plate evolution due to collision of several island arcs and now all of them are outliers of the ancient oceanic crust. The technique of morphostructural analysis developed by the authors has allowed solve the inverse problem, and under morphological approach split all largest depressions on two main genetic types that confirm received geodynamic conclusion
(in Russian, стр.0, fig. 0, tables. 0, ref 0, Adobe PDF, Adobe PDF 0 Kb)
Vol. 20 (2017 year), No. 1, DOI: 10.21443/1560-9278-2017-20-1/1
Kozlov N. E., Fomina E. N., Martynov E. V., Sorokhtin N. O., Marchuk T. S.
On reasons of specific composition of the Keivy domain rocks (the Kola Peninsula)
The Keivy domain differs from the other structures of the Kola region by the specific composition of the metamorphic complexes, the presence of the oldest for the region alkaline granites and gabbroanorthosites associated with them as well as by the presence of unique mineral deposits. The previous studies of the Keivy structure showed that within this structure there are metasedimentary formations that differ from both Early Precambrian metasedimentary rock associations of the Kola region and Phanerozoic sedimentary complexes in the content of titanium and the ratio Al2O3/SiO2. The present study confirms the correctness of this conclusion. The authors have attempted the search of the generalized indicator (trend) describing the nature of changes in the chemical composition of rocks in the transition from Low-Ti to High-Ti varieties of rocks (with simultaneous increase in the ratio Al2O3/SiO2). To solve this problem the method of search of differences in the specified number of sets has been used with the partial order relation introduced by the researcher. The formations of the same type and age, namely metapelites of the Chervurtskaya suite of the Keivy series, have been chosen as the informational basis. Such indicator has been found. It describes the process which besides a significant titanium input was accompanied by a simultaneous increase in the content of CaO and decrease in the content of Al2O3, ?Fe, and Na2O. It must be emphasized that the obtained trend is not related to the supergene processes characterized by the similar behavior of titanium with aluminum and iron which is especially clearly exhibited in the formation of crusts of weathering. The location on this generalized indicator of the points of rock compositions of all strata of the geological section of the Keivy domain taken far or close to alkaline granites corresponds to the position of less or more titaniferous rocks, thus confirming the assumption of a metasomatic alteration of the latter. The fact that all the metasedimentary Keivy formations are subjected to metasomatic alteration most probably related to the Archean complexes of alkaline granites, which is confirmed by direct geological observations of the relationships of the Lebyazhinskiye and Chervurtskiye rock complexes with alkaline granites, allows us to speak about their Archean age.
(in Russian, стр.12, fig. 4, tables. 1, ref 29, Adobe PDF, Adobe PDF 0 Kb)
Vol. 20 (2017 year), No. 1, DOI: 10.21443/1560-9278-2017-20-1/1
Sorokhtin N. O., Lobkovsky L. I., Kozlov N. E.
Metallogeny of subduction zones
The paper deals with the multistage mechanism of the Earth's crust enrichment in ore elements in underthrust zones. The processes of metamorphism and the formation of hydrothermal solutions at pulling of the watered oceanic lithospheric plate into the subduction zone have been described. Some physical and chemical transformation regularities of structural-material complexes in these areas and mechanisms of the formation of ore deposits have been discussed. Spatio-temporal patterns of the localization of a number of endogenetic and exogenetic deposits have been described using metallogeny of the Ural and the Verkhoyansk-Kolyma Fold Belts as an example. It has been shown that in nature there are several effective mechanisms of the enrichment of the crust in ore minerals. One of them is the process of pulling into subduction zone of metalliferous sediments and ferromanganese crusts as well as seabed nodules, their metamorphic transformation, partial melting and transition of ore components into magmatic melts and mineralized fluids. In the future this leads to the release of ore material by magmas and hydrothermal solutions into the folded formations of island-arc and Andean types and the formation of igneous, metasomatic and hydrothermal deposits. Another, yet no less powerful natural mechanism of a conveyor enrichment of the crust in ore elements is the process of destruction and sedimentation of mineral deposits formed in the folded areas as well as the formation of placers and their transfer to the marginal parts of the continent. Later, during the collision of active and passive margins of two lithospheric plates, such as the collision of the Kolyma Massif with the eastern part of the Siberian craton in the middle of the Mesozoic there was a thrusting of a younger lithospheric plate over a more ancient one. As a result, the sedimentary sequences of the passive margin of the Siberian plate were submerged and partially melted by the basic magmas intruded in the bottom of the cut. This led to the transition of a part of ore elements from placers to igneous rocks of granitoid composition and fluid solutions, thereby forming magmatic, metasomatic and hydrothermal mineral deposits. Cyclic enrichment of the Earth's crust in this way can repeatedly manifest itself in the history of the Earth and lead to the enrichment of ore deposits from the ancient complexes to the young ones. Studying processes of geodynamic evolution of the structural-material complexes of continental and oceanic lithosphere is important to understand the processes of ore genesis in the Earth's crust. Most endogenetic deposits are closely connected with the processes of metamorphism, magmatism and hydrothermal activity and are usually formed at the margins of lithospheric plates. A part of exogenetic deposits is also genetically connected with endogenetic and is formed due to their destruction. The regularities of ore genesis in underthrust zones described in the paper cover only a part of the natural processes of the Earth's crust enrichment in ore minerals. The paper has also focused on polycyclic and conveying mechanisms of the formation and transformation of ore elements in subduction zones, as well as on the mechanism of remobilization of orebearing deposits and their joint transfer to the upper structural layers of the folded system and the formation of ore-bearing volcano-plutonic associations.
(in Russian, стр.18, fig. 5, tables. 0, ref 35, Adobe PDF, Adobe PDF 0 Kb)
Vol. 22 (2019 year), No. 1, DOI: 10.21443/1560-9278-2019-22-1
Sorokhtin N. O., Kozlov N. E., Kalatchev V. Yu.
The first find of diamond on the Sredny and Rybachy Peninsulas in the north-eastern Baltic Shield
The regular features of the region's spatial-temporal evolution have been discussed. Based on geodynamic analysis and the time scale of the crust formation in the eastern Baltic Shield, it is defined, that the most promising search areas for diamond-bearing rocks are intersections of deep lithospheric faults and discovered belts of possible diamond-bearing kimberlitic magmatism. The paper suggests the most promising search areas for diamond-bearing kimberlitic explosion pipes that can be united in the single diamond-bearing Norwegian-Mesensky belt. Prospecting for diamonds was carried out in the area of the Rybachy and Sredny Peninsulas in 2005–2007. Detailed decoding of large-scale aerial photographs and in situ measuring of fractures in the northern margin of the Sredny Peninsula allowed defining prospective intersection nodes of deep faults. Heavy mineral concentrate has been sampled here and indicated diamonds and associated minerals. They can suggest either native wash-out origins, or immediate scouring of Paleo-marine terraces that used to be rich in these minerals. No magmatic explosion pipes of the kimberlitic composition have been found here. It can be due to a lack of geological data on the region obtained by large-scale geophysical methods. The diamond finds have made it possible to recommend enhancing such investigations and paying more attention to this issue. We take into account that the Riphean sedimentary complexes of the Rybachy and Sredny Peninsulas are formations of the passive continental margin at that time and the watershed of the Musta-Tunturi Range is close to the study area. Based on that, we suggest that the matter transfer was not significant, just first km or, probably, first tens of km. Therefore, bedrocks of diamond-bearing explosion pipes should be prospected for close to the location of the diamond find
(in English, стр.12, fig. 11, tables. 1, ref 5, 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. 26 (2023 year), No. 1, DOI: 10.21443/1560-9278-2023-26-1
Kozlov N. E., Sorokhtin N. O., Marchuk T. S.
Evolution of the Keivy domain in the Precambrian
Detailed geological and petrogeochemical studies carried out using the techniques developed by the authors have made it possible to complete the picture of the formation of supracrustal complexes of the Keivy structure. The studies have shown that the metasedimentary complexes of the Chervurt and Vykhchurt suites were formed mainly due to the material of the underlying strata. In the development of the Vykhchurt Formation, starting from its upper part, the material of the domains surrounding the Keivy takes an active part. The authors have come to the conclusion that at least the middle part of the Keivy section was formed as a result of washing and redeposition of the material of the structure itself, it confirms the conclusions about the presence of redeposited weathering crusts within the Keivy. The results obtained testify to the correctness of the earlier conclusion about the formation of the Keivy structure under conditions most similar to the middle massifs, and to a certain extent explain the formation of a giant deposit of aluminum raw materials within the Keivy.
(in Russian, стр.6, fig. 1, tables. 2, ref 12, AdobePDF, AdobePDF 0 Kb)