Shumlyanskyy L.V.
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine
Language: Ukrainian
Geochemistry and ore formation 2012, 31-32: 136-143
https://doi.org/10.15407/gof.2012.31.136
Paper deals with results of the isotope age investigation of zircons from quartzite of the Kosharo-Oleksandrivka suite of the Bug Series, Pobuzzhya. Besides this, data on Hf isotope composition in zircons, as well as whole-rock geochemistry and Sr and Nd isotope compositions in quartzite are also reported. It is shown that youngest of the detrital zircons are ca. 2540 Ma. This age corresponds to the maximal time of sedimentation. Even younger zircon grains (up to 2031 Ma) are of metamorphic origin. Oldest of the zircons found in quartzite is 3245 Ma. As shown by Hf isotope composition, zircons are probably derived from two different sources. Most of the results are located along evolution line that corresponds to Lu/Hf = 0 and intersects line of evolution of Hf isotope composition in depleted mantle at 3.32 Ga. Hf isotope composition evidences of juvenile origin of these zircons. Grains that belong to the second variety are originated from another, younger source. Nd model ages indicate origin of quartzite due to destruction of Neo- and Meso-Archaean rocks of mainly felsic composition. Distribution of zircon ages in quartzite of the “Bila Skelya” outcrop differs significantly from the quartzite that crops out nearby Kosharo-Oleksandrivka village that belongs to the same stratigraphic unit. Most probably, these were derived from different sources and have different metamorphic history. There are no evidences of the presence in the studied quartzite of the material derived from the rocks of the Paleoarchaean Dniester-Bug Series.
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