GEOCHEMICAL CHARACTERIZATION OF PRECAMBRIAN MAGMATIC SUITES OF THE SOUTHEASTERN MARGIN OF THE EAST EUROPEAN CRATON, SOUTHERN URALS, RUSSIA

Abstract

The Bashkirian anticlinorium in the western slope of the southern Ural Mountains, Russia, exposes the poorly understood magmatic units of the southeastern margin of the East European craton. Volcanic and intrusive rocks were analyzed for major and trace elements (91 samples), and the data used to correlate volcanic suites and to correlate poorlydated intrusive suites with the volcanic suites, and also assess geodynamic setting. Five distinct geochemical suites were identified although their ages are not always wellconstrained 1) Early Mesoproterozoic (lower Riphean, type section) Ai formation volcanics (ca. 1650 Ma) situ, and compositionally similar sills cutting the Early Mesoproterozoic (Lower Riphean) Satka formation 2) Late Mesoproterozoic (Middle Riphean) units including the Mashak volcanics, dykes of the Bakal quarries cutting the Mesoproterozoic (uppermost Lower Riphean), the Berdyaush rapakivi pluton and crosscutting dykes (grouped as the Mashak Igneous Event) 3) Dykes and sills cutting basement of the Taratash complex as exposed in the Radashni quarry and a high Mg dyke in the Bakal quarry. 4) dykes cutting Neoproterozoic (Upper Riphean) units and finally 5) Late Neoproterozoic (Vendian) units consisting of basalts, andesite and dacite lavas and tuffs of the Arsha formation.. A precise U-Pb age of 1385,3±1,4 Ma for the Bakal dyke represents the most precise estimate available for the Mashak Igneous event. The Mashak event may represent the Mesoproterozoic breakup of the East European craton, and can be correlated with the Midsommerso sills - ZigZag Dal volcanics in northern Greenland.