ИСТИНА

The Early Carboniferous volcanic complexes are widespread in the Southern Urals tectonic province, a fragment of the western (in present-day coordinates) segment of the Central Asian Orogenic Belt. Here, the Lower Carboniferous sequences crop out within the following N-S-trending tectonic zones (from west to east): Magnitogorsk, Ui River, East Ural, Transural, and Valeryanovka. We have got new isotope ages for the Early Carbonifrous volcanic rocks of the Magnitogorsk zone. We describe and discuss the geology, geochemistry and paleomagnetic data of the Early Carboniferous volcanic complexes on the base of published and newly obtained data, with implications to paleo-tectonic models. The western zones are dominated by bimodal rhyolite-basalt series, with the basalts relatively enriched in Ti and Zr but depleted in Nb. The volcanics of the Valeryanovka Zone belong to typical evolved calc-alkaline series, with the derivatives depleted in Ti and Nb. Almost all selected groups of volcanics bear geochemical signatures transitional between those of subduction-related and intraplate igneous rocks. The relative enrichment of the volcanics of the East Ural and Transural Zones may be interpreted as a result of magma generation at a greater depth and / or the involvement of locally enriched material of the subcontinental lithospheric mantle. The magnetic poles obtained for the Early Carboniferous volcanics of the Magnitogorsk zone do not coincide with those for the East European Platform. This may be related to the numerous shears widely developed in the Southern Urals and the rotation of single blocks. However, according to paleomagnetic data we suggest that the Magnitogorsk zone was accreted to the stable East European Platform by the Early Carbonirefous time.