NEW DATA ON THE AGE OF SUBALKALINE MAGMATISM AT THE EASTERN MARGIN OF THE EAST EUROPEAN PALEOCONTINENT AND ESTIMATION OF THE RATE OF LONGITUDINAL OPENING OF THE EARLY PALEOZOIC RIFT

Abstract

Subalkaline igneous rocks are widespread in the Main Ural Fault Zone as a chain of dikes and minor intrusions that crosscut the Ordovician sequences deposited at the eastern (Uralian) margin of the East European paleocontinent. In the Polar Urals, the subalkaline rocks belong to the Paipudyn rhyolite complex, the Manitanyrd trachybasalt–trachyrhyolite complex, and the Pozhem rhyolite complex. In the Subpolar and northern Urals, they occur in the Bol’shepatoka and Malinovka trachyrhyolite complexes. The Verkhneserebryanka trachybasalt–trachyte complex, the Vaganovka gabbro–syenite complex, the Kordonokamenka alkali granite complex, and the Belokamenka syenite complex are recognized in the central Urals. Most of these complexes are still poorly characterized in terms of petrography, geochemistry, and reliable isotopic dating. The age of some complexes is based only on random K–Ar determinations of whole-rock samples. These complexes are attributed to tectonomagmatic reactivation in the Ordovician, Carboniferous, and Triassic–Jurassic.