Archean metavolcanic rocks from three greenstone belts (Suomussalmi, Kuhmo and Tipasjärvi) of eastern Finland have been subject to a detailed geochemical study which leads to a discussion of their petrogenesis and the problem of compositional heterogeneity in the Archean mantle. Lithostratigraphically, the greenstone belts are roughly divided into a lower and an upper volcanic sequence. Rocks of komatiitic and tholeiitic compositions are restricted to the lower sequence, while andesitic tuffs, dacite-rhyodacite lavas and minor basalts of alkaline affinity occur in the upper sequence. All rocks from the greenstone belts have been subject to regional metamorphism of the upper greenschist facies to the lower garnet amphibolite facies. Consequently, the geochemical distinction of original magma types and the discussion of petrogenesis have relied heavily on the abundances of less mobile elements, such as TiO2, rare earth elements (REE), and some transition metals (e.g. Ni and Cr).