Authors: G.V. Artemenko

Summary: The monograph presents the results of original geochemical studies of Archean sedimentary-volcanogenic rocks of the greenstone belts and intrusive complexes of the Azov and Middle Dnipro megablocks of the Ukrainian Shield from the Pravoberezhny region to the Eastern Azov, which were formed between 3.5 and 2.6 billion years ago. It is shown that in the West Azov block with Eoarchean-Paleoarchean basement (3.97-3.3 Ga), volcanism in greenstone structures was bimodal, and in the greenstone structures of the Middle Dnipro megablock with Paleoarchean-Mesoarchean basement (3.3—3.2 Ga), it was polymodal, with a wide occurrence of andesites. It was determined that the komatiites and basalts of the greenstone structures of the Azov and Middle Dnieper megablocks were melted from the primitive (PM) and deep-depleted mantle (DEP). The geodynamic conditions for the formation of komatiites and basalts corresponded to those of modern oceanic or marginal continental plateaus. No differences were found in the composition of metamorphosed komatiites and basalts of greenstone structures of the Middle Dnieper and West Azov blocks. It was established that quartz diorites and tonalites of Paleoarchean (3.5—3.3 Ga) age have contrasting geochemical characteristics. Some of them were probably formed during the melting of the thickened basaltic crust, and others – as a result of the melting of metabasites with restite, which included garnet and/or hornblende. Tonalites of the Mesoarchean age of the Sura complex of the Middle Dnieper megablock and the Shevchenko complex of the Azov megablock have typical geochemical characteristics for TTG. It was determined that the high-potassium felsic volcanics of Bilozerka series were formed during the melting of older granito-gneisses of the basement with a Sm-Nd model age TNd(DM) = 3.3-3.1 Ga. They were probably formed as a result of activation of the mantle under the Middle Dnieper Block in the Neoarchean-Paleoproterozoic. Early TTG magmatism (3.1—3.0 Ga) occurred simultaneously in the Azov and Middle Dnipro megablocks. Later TTG (2.92—2.83 Ga) was formed only in the West Azov block, and in the Middle Dnipro block, these phases are represented by potassium-sodium crustal granites.

Reading audience: For geologists of industrial and scientific organizations.

ISBN 978-966-00-1946-1

DOI: https://doi.org/10.15407/978-966-00-1946-l

Book project: Scientific book

Responsible institutions: M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of NAS of Ukraine

Published: Kyiv

Size in pages: 164

Print run: 100