Youngest Precambrian dyke rocks in North Karelia, east Finland

Abstract

The dykes which are the subject of the present paper are the youngest rocks in the area. These include microtonalite dykes about 1850 Ma old and lamprophyre dykes about 1830 Ma old. A total of 18 modal and chemical analyses (mainly by XRF) were made on the microtonalite dykes, showing that they vary largely in composition. Only a few lamprophyre dykes are encountered and one of them was analysed chemically. The dykes are mesocratic biotite-lamprophyres.