On Some Age Relations in the Pre-Cambrian of Southwestern Sweden

Abstract

Abstract In view of forthcoming radiological data on the ages of rocks from S.W. Sweden an attempt is made to reconstruct the geologic history of this region on the basis of purely geological and petrological evidence. It is shown that there exist two paragenetically different groups of granitic pegmatites. One of these is, in its distribution, clearly related to the Bohus granite. The Hogsbo pegmatite deposit near Gothenburg paragenetically belongs to this particular group. The other group of pegmatites is related to the Askim granite on the basis of field evidence in the Gothenburg area. The Askim granite is shown to be older than the Bohus granite, since it is cut by swarms of meta-dolerites (the Koster dikes), which in turn are older than the Bohus granite. On the other hand the Askim granite is shown to be younger than quartzdiorite dikes which intrude the Frolunda granite-gneiss. Likewise it is younger than bodies of metahyperite which are most probably intrusive into the Lundby granite-gneiss. Henc...