Petrogeochemical characteristics of mafite-ultramafite rocks of the southern part of the Marunkeu block (Polar Urals)

In the Polar Urals, in the Central and Western tectonic zones, small bodies of mafic-ultramafic rocks are widespread. Their age, petrographic and geochemical features are poorly studied. The paper presents the results of petrographic and petro-geochemical study of muscovite-albite-epidote-amphibole and pyroxene-amphibole-chlorite rocks of the southern part of the Marunkeu block of the Polar Urals, localized in the Middle Riphean sediments of the Nyarovey series and presumably belonging to the Ampelshor complex (O1-2). The primary composition of metamorphites corresponded to high-magnesian, low-titanic, low-alumina, and potassium-sodium tholeiitic hornblende gabbro-dolerites (dolerites) and peridotites formed either from primary magmas melted at the level of the spinel facies from the depleted mantle under the influence of an aqueous fluid, or by intra-chamber differentiation. In terms of the contents of rare and rare-earth elements, they differ from continental riftogenic formations (in particular, dolerites of the Orangyugan-Lemva complex) and are close to the tholeiites of the ensimatic island arcs.