Igneous and metamorphic geology of the Husfjord area, Soroy, northern Norway

Abstract

The Husfjord area of Soroy essentially comprises a plutonic igneous complex which has been emplaced into Eocambrian meta sediments during the Caledonian orogeney. The metasedimentary envelope of the complex consists mainly of a sequence of psammites, pelites, semi-pelites, calc-silicate-schists, and metalimestones, which have suffered a prolonged regional metamorphism and two principal episodes of deformation. The regional metamorphic event commenced before the first folding episode, reached its peak in the almandine-amphibolite facies between the deformation episodes, and waned during the second period of folding. The various members of the igneous complex were emplaced synchronous with these metamorphic and tectonic events. Contact metamorphie effects produced by some members have been superimposed upon those of the regional metamorphism. The earliest member, the Husfjord metagabbro, was intruded towards the end of the first deformation episode, and has undergone the highest grades of regional metamorphism. A norite and a suite of diorites were emplaced during the second deformation episode and these have only suffered a low-grade regional metamorphism. The Husfjord metagabbro and the diorite complex were emplaced essentially by a mechanism of permissive intrusion. The latest members of the igneous complex were the Vatna gabbro, the Slatten gabbros, and a number of minor intrusions including perthosite sheets, basic dykes, and nepheline-syenite pegmatites. The main diorite suite appears to have developed from a dioritic melt, which was generated deep in the crust by the syntexis of sialic material with basic magma emplaced from beneath. Metamorphic mineral paragenesis in pelitic hornfelses suggests that the depth of emplacement of the Husfjord plutonic complex was in the order of 23 km.