Geological Structure, Composition, and Age of the Ondomozero Massif, Northeastern Baltic Shield

摘要

The discovery of low-sulfide PGE mineralization in the Early Proterozoic (Sumian) layered peridotite-pyroxenite-gabbronorite intrusions (Monchepluton, Fedorova-Pana, Mt. General'skaya, Lukkulaisvaara, and others), which are restricted to the Pechenga-Var-zuga and North Karelian riftogenic systems of the Baltic Shield, stimulated interest in similar, though less studied objects. One of these is the Ondomozero Massif located in the eastern part of the Belomorian geoblock. This massif (180 km~2 in area) is traditionally ascribed to the Early Karelian layered intrusions (the Fedorova-Pana Tundra intrusion petrotype). However, the internal structure, petrography, and composition of the rocks, as well as the age and mineragenic potential of the massif itself are poorly studied. We performed detailed geological-petrological investigations that have made it possible to significantly refine the geological structure and composition of the massif and to ascertain its age.