A syenite porphyry dyke intrudes the gneisses of the Western Gneiss Region. The dyke is undeformed and unmetamorphosed. The texture, mineralogy and chemistry show great similarities to the nordmarkite-ekerite series of the Permian intrusive rocks of the Oslo Region. An age of 297 ± 8 m.y. has been determined by the Rb-Sr isochron technique.
A post caledonian syenite porphyry dyke in the western gneiss region, Tustna, central Norway