The field relationships of basic and ultrabasic masses in the basal gneiss complex of Stadlandet and Almklovdalen, Nordfjorden, Southwestern Norway.

The field occurrence of hornblende gneisses and garnet amphibolites, eclogites, anorthosites, and dunites with garnetiferous and eclogitic layers is described. The hornblende gneisses and garnet amphibolites are thought to be the normal basic members of the gneiss complex and reflect its grade of metamorphism. The other basic and ultrabasic rocks are foreign to the gneiss complex and are probably solid introductions. These masses form lenses of varying size within the gneisses. The gneisses belong to the almandine amphibolite facies and have a complex tectonic history, having been folded three or four times in the Caledonian orogeny. Metamorphic or metasomatic events are correlated, in so far as is possible, with various structural events. The relationships in time of the basic and ultra basic rocks are deciphered from their relationships to these structural and metamorphic events and from mutual contacts between various rock types. It is suggested that the eclogites in the gneiss were introduced at a relatively early stage in the tectonic history and have since been boudined. The dunites with eclogitic layers on the other hand are late and lie in a cross-cutting shear zone. The anorthosites are tentatively placed in an intermediate position. The eclogites, dunites, and anorthosites are thought to be derived from deep crust or from mantle materials.