NEW ISOTOPIC AND PALAEOMAGNETIC DATA ON THE EARLY CARBONIFEROUS BEREZOVKA COMPLEX OF THE MAGNITOGORSK ZONE (SOUTHERN URALS). ARTICLE 1. ISOTOPIC DATES AND GEOCHEMICAL CHARACTERISTICS

This series of articles presents the first isotopic and palaeomagnetic data for rocks from the Early Carboniferous Berezovka complex of the Magnitogorsk zone. The aim of the work was to develop kinematic reconstructions for the time of its formation. For this purpose, in the vicinity of Bogdanovskoye Village, a set of 93 oriented samples was taken from nine sites; besides, two sets of 8 and 3 samples were collected respectively for geochemical and isotope-geochronological studies. Paper 1 presents the first isotopic ages for felsic volcanics from the Berezovka complex: rhyodacites – 348.5±3.1 Ma, fluidal rhyolites – 350.7±2.9 Ma, dacitic ignimbrites – 340.6±2.8 Ma, as well as geochemical characteristics for these rocks. The material composition of the studied volcanics is consistent with that of the rocks typical for the Berezovka complex. According to the newly obtained dates, Early Carboniferous volcanism started almost simultaneously throughout the southern part of the East Magnitogorsk zone and earlier than the date obtained paleontologically for its eastern part before. The newly obtaied data allow us to conclude that active volcanism in this region may have begun during the Rezhian substage of the Early Turonian.

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