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Information × Registration Number 0210U000608, 0108U003819 , R & D reports Title Lithospheric evolution of the Ukrainian and Baltic Shields in early Precambrian: general features and basic geodynamic differences popup.stage_title Head Shcherbak M. P., Registration Date 01-03-2010 Organization M.P. Semenenko Institute of Geochemistry, mineralogy and Ore Formation popup.description2 According to the project the analysis of geological structure and material composition of Archean cratons (megablocks) of the Ukrainian and Baltic Shields is carried out. It is shown, that greenstone structures of the Ukrainian Shield were formed throughout a short interval of time from 3,2 to 3,0 Ga. From 2,8 till 2,6 Ga thick weathering crusts are formed within the Peri-Dnieper megablock, which were the source for accumulation of terrigenous rocks of the Krivoy Rog suite (2,6-2,0 Ga). Greenstone belts of the Karelian craton are formed from 3,1 to 2,75 Ga. Geological and geochronological data testify to different trend of lithospheric evolution of this region. This fact explains difference in ages of iron deposits of Krivoy Rog and Kostomuksha regions. By results of ion-ionic microprobe investigations (SHRIMP) carried out on the rocks of Vasilkovsky site of Orekhovo-Pavlograd sutural zone, it is established, that tonalite and garnet-biotite gneisses (ultra-mylonites after tonalite) show the age of 3500 Ma. The magmatic and /or metamorphic event is occured about 3400 Ma, that results in formation of new generation of zircon with the recrystallization of magmatic grains of early zircon generation. At present uranium-lead classical and ionic-ionic (SHRIMP) methods paleoarchean formations (3,6-3,2 Ga) are unequivocally established on two sites, Orekhovo-Pavlograd interblock zone of eastern part (Novopavlovsk and Vasilkovsky sites) and Gajvoron-Zavalevsk structure of Dnestrovo-Bugsk megablock of western part of the Ukrainian Shield. The data reported with taking into account the results of previous investigations indicate the fact that Dnestrovo-Bugsk and Orekhovo-Pavlograd tectonic structures are synchronous in time with polycyclic and prolonged nature of their formation (3,6-2,1 Ga). On the basis of new geochemical and isotopic data two mantle sources of meso-and neo-archean basic rocks of the Ukrainian and Baltic Shields are established and characterised that shows isotopic-geochemical heterogeneity of mantle in time and space under both shields. The results of studying of rare, rare-earth and high-charge elements in Archean metabasalts from greenstone belts of Peri-Dnieper and Near-Azovian regions as well as Kola and Karelian provinces has shown, that among possible source of basalt formation were primitive mantle (PM) and deeply depleted mantle (FOZO). This fact indicates on similar geodynamical conditions of Archean terraine formation within both these shields. It is established, that Al-depleted and Тi-enreached komatiites (Barberton type) are distributed within Near-Azovian megablock, while Al-undepleted and Ti-depleted komatiites (Yilgarn type) are distributed within Middle Dnieper megablock. We propose to do some certain corrections in chronostratigraphic scale of early Precambrian of Ukraine which are specified in corresponding chapters of this report. Moreover, perspective complex problems for specification of geological time scale of early Precambrian are planned, the main things from which are: 1) Paleoarchean - specification of the upper and lower age boundaries of Aul suite. 2) Mesoarchean - identificationof of lower age boundary of Sura suite, Konska group. 3) Neoarchean - identification of the lower age boundaries of Bugsk group by U-Рb method on zircon syngenetic to metapellites which occur in the section of metasedimentary rocks of Bugsk group The results of SRW are used in the industrial organisations and institution Minecoresources and NAS of Ukraine, and also by National Stratigraphic Committee of Ukraine and Stratigraphic Committees of the adjacent countries, first of all - Russian and Belarussian committees, for making geological, tectonical and metallogenic maps. Product Description popup.authors Артеменко Геннадій Володимирович Бахмутов Володимир Георгійович Демедюк Валентина Валентинівна Пономаренко Олександр Миколайович Самборська Ірина Анатоліївна Степанюк Леонід Михайлович Цимбал Степан Миколайович Шумлянський Леонід Владиславович popup.nrat_date 2020-04-02 Close