Geology and age relations on Vaeroy, Lofoten, north Norway

Two westward-dipping thrust faults divide Vaeroy into three blocks. The eastern block consists of granulite facies gneisses, migmatized, retrograded, and deformed during at least one later folding episode. The rocks between the two thrust planes are mica schists, garnet amphibolites, quartzofeldspathic gneisses, and pegmatites, all of which are strongly mylonitized. The uppermost block consists of strongly flattened blastomylonites surrounding relict lenses of less-deformed basement rocks, similar to those of the lower block. Rb/Sr data confirm the relation of the lower block to the Lofoten-Vesteralen mangeritic intrusives (1700-1900 m.y.) and suggest that the mylonitic rocks of the middle block were metamorphosed at 900-1000 m.y. The formation of the blastomylonites, and their subsequent emplacement on top of the mylonitic gneisses, reflect two stages of overthrusting, probably of early and late Caledonian age. -G.R.