K-Ar data are presented for the age of the metamorphism of the pre-Caledonian basement rocks which are exposed in a large tectonic window within the Caledonide orogen of West Finnmark. Metamorphic hornblendes separated from metabasites of the Raipas suite in the Komagfjord Tectonic Window yield ooncordant radiometric ages which date the peak of regional metamorphism at about 1840 M.a., thus confirming the suggestion that this suite is of Svecokarelian age. The metabasites are considered to represent the northward continuation, beneath the Caledonian nappe pile, of greenstone supracrustal beits which developed in N. Finland, N. Sweden and the Finnmarksvidda of N. Norway during the Early Proterozoic. These Svecokarelian greenstones are distinctly different in age and lithology from the greenstone beits of E. Finland.
K-Ar age determinations on the Raipas suite in the Komagfjord Window, northern Norway