The first determination of the andesite-dacite complex isotope age of the Middle Urals Еastern zone

In the paper are given the results of the first performed U-Pb dating of zircons from dacites and volcanic paleostructure of the Eastern zone andesite-dacite complex of the Urals orogen middle-uralian part, consisting of retro-overthrusted and cover-folded structural subzones. Volcanogenic complex, including vent and nearvent facies, occurs among flyschoid and carbonate deposits with the Middle Devonian fauna in cover-folded structural subzone forming an extreme eastern orogen limitation. Zircon grain age made up 389±5,6 Ma that also correlates with Middle Devonian. Consequently the formation of sedimentary and volcanogenic complexes occurred in a close age interval, but judging by their composition and structure, in different environmental conditions. Sedimentary formations accumulated in shallow basins, and the volcanic ones have been formed, apparently, under sub-areal conditions surrounded by the shallow sea basin. It is assumed that the manifestation of andesite-dacite volcanism, most probably, testifies to the spatial and age displacement of geodynamical and facies conditions to the eastern periphery of the orogen.