Title

A. V. Krylov, R. Marquet

Marine mollusks of Atlantic origin from the Pliocene – Eopleistocene deposits in western Russian Arctic and their biostratigraphic significance. Mollusks of Astarte, Cyrtodaria, Mya, Panomya genera

Massif Vuruchuaivench in Monchegorsk pluton composed with gabbronorites, anorthosites, metasomati-zed in varying degrees, as well as propylitized. Massif is platinum-bearing with an average grade of 2.5 ppm of PGM, with a maximum up to 19 ppm of PGM. Age of igneous rocks of the Monchegorsk pluton 2,500 Ma, but age of his southern framing massifs still debatable. To solve this problem, propylites sample was taken from massif Vuruchuaivench and using the Rb-Sr isotopic system, determine the age 2470 ± 130 Ma. Isotopic data indicate a slight part of a crustal component in formation of rocks and ores in massif.
Key words: age of the rocks, Rb-Sr isotopic system, Monchepluton, propylites.