Ivanovskii

The Ivanovskii complex is located at the northeastern end of the Kola aulocogen on the northeastern coast of the Kola peninsula in the area of the Ivanovka Gulf. It is represented by several clusters of dykes and small intrusions as well as tuffs and lavas of alkaline and melilite picrites, lamprophyres, alkaline trachyte, olivine melteigite porphyry, olivine pyroxenite and melteigite. These rocks are concentrated in a northeasterly-trending zone embracing the area of the Drozdovka Gulf, the northeastern extremity of the Ivanovskii Peninsula and the Island of Novokuev. The zone is 6-8 km broad and extends along the deep fault zone of the Kovdor-Kharlov lineament. The extrusive rocks are represented by tuffs, tuffisites, lavas and lava breccias of alkaline trachyte and nepheline trachybasaltoids, which are part of a volcanogenic sedimentary series that is preserved as relics in a linear zone extending over 18 km. The series is subhorizontal and 30-40 m thick. The intrusive rocks comprise small plugs and necks of 0.2-4 km2. The largest plug in the area has a circular structure and is composed of olivine melteigite and olivine pyroxenite with zones of eruptive breccia. Small necks of peralkaline trachyte (e.g. 20x40 m) and a diatreme (20x30 m) of picrite pass gradually into carbonatite. The diatreme fragments are of sandstone, olivine pyroxenite, melteigite porphyry, alkaline trachyte and their tuffs, monchiquite and melanephelinite. The cement of the breccia is of both picritic and carbonatitic composition. Among the dyke series alkaline lamprophyres are the most abundant (77%) with alkaline picrites comprising 13% and alkaline trachytes 10%.