Search academic texts

Information × Registration Number 0219U005378, 0116U002906 , R & D reports Title Prospect estimation of indigenous diamond bearin potential in central part of Novograd-Volyn block of the Ukrainian Shield popup.stage_title Head Shcherbak Mykola Petrovych, Registration Date 20-09-2019 Organization nstitute of Geochemistry, Mineralogy and Ore Formation popup.description2 The research report contains the results of the three-year (2016-2018) research project. Initially planned for five years, the project remained uncompleted due to the premature death of its main executors and initiators. The research was performed at the M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation. The objects of the study are alkaline-ultramafic rocks of the central part of the Novohrad-Volynsky block of the Ukrainian Shield, as well as xenocrysts of the mantle minerals found in these rocks. The main tasks of the work: determination of petrographic, mineralogical and geochemical features of alkaline-ultramafic rocks in the research area; determination of the conditions of the initial melts formation and, based on that, their potential with respect to diamonds; determination of the prospects of the central part of the Novohrad-Volynsly Block of the Ukrainian Shield with respect to diamonds. Alkaline-ultramafic rocks have attained a wide distribution in the central part of the Novohrad-Volynsky Block of the Ukrainian Shield (the Northwestern part of the Shield), forming a whole series of small intrusions and dyke-like bodies. The urgency of the study of these rocks is defined by the presence of the early Proterozoic detrital zircons in the Topilnya Series sediments, which fill in the located nearby Bilokorovychi basin. Therefore, it is extremely important to determine the age of alkaline-ultramafic rocks as possible sources of diamond (or as rocks related to the diamond sources), as well as to determine the sources of the primary melts, to establish their potential concerning diamond. In the course of the research, it has been found that at least a part of the xenocrystal minerals (chrome spinelides) was formed at the mantle conditions; some clinopyroxenes also crystallised either in the upper mantle or in the lower crust. The composition of the initial melts corresponded to alkaline pyroxenites, which had high magnesia, high content of Cr, Ni and Cu. At the same time, they were characterised by a high amount of alkalis and SiO2. The features of the distribution of trace elements in the investigated rocks indicate that they were formed due to the low degree (first percents) partial melting of moderately depleted mantle garnet-containing lherzolites, which experienced some mantle metasomatism immediately prior melting. The age of the formation of alkaline-ultramafic rocks in the central part of the Novohrad-Volynsky block, according to geological and geochemical data, estimated in 1780-1790 Ma. All of these intrusions were formed from the same, or a series of geochemically similar, magmatic centres, located in the lower part of the lithosphere. The presence of alkaline-ultramafic rocks of deep origin in the Novohrad-Volynsky block and their affiliation with the hypabyssal facies indicates the possibility of preserving of little eroded pipes and dykes of kimberlites in this area, whose indicator minerals often occur in the terrigenous rocks of the sedimentary cover. The results of the research can be applied in the work of geological enterprises of Ukraine that carry out geological surveys and prospecting for diamonds. Product Description popup.authors Цимбал Степан Микодайович Цимбал Юрій Степанович Шумлянський Леонід Владиславович Щербак Микола Петрович popup.nrat_date 2020-04-02 Close