A significant part of the area of the Pechenga district is composed of sedimentary-volcanogenic strata, representing alternation of low thicknesses of sedimentary-metamorphic rock packs and thicker volcanogenic covers. Middle Proterozoic metagabbro-diabase intrusions and late Proterozoic intrusions of basic and ultrabasic rocks are confined to the rocks of the Pechenga series. To the north and south of the Pechenga Series are developed gneisses and strongly metamorphosed rocks of the Archean.