Some composite dikes in Sweden

Abstract

Abstract Some late-plutonic, net-veined composite dikes occur both in the older Svecofennian calcalkaline ‘primorogenic’ igneous suite and in the late Svecofennian, syntectonic, somewhat more alkaline Småland-Värmland suite. Earlier developments in these two major suite generations are characterized by large-scale magma-mixing and magma-mingling. Because mafic enclaves are very rare in the ‘serorogenic’ S-type granites some scattered findings of composite dikes related to these granites are also discussed. Based on comparison with models published elsewhere, it is suggested that mafic magmas are involved in the generation of all major groups of Svecofennian granites in Sweden; in the case of the S-type granites probably mainly as a heat source. A prominent fracture pattern in the Småland-Värmland granitoids can be related to the late crystallization phase since the composite dikes occur both parallel to the magmatic flow directions and closely associated with the fracture pattern.