Chronologie et deformations des filons basiques dans les formations Precambriennes du sud de la Norvege.

In order to establish a relative chronology in the Bamble area (Precambrian) detailed observations were carried out on a small island in the South of the Levang peninsula, south of Kragerø. Granite gneisses probably deriving from supracrustal rocks are eut by three generations of basic dikes, the two oldest of which are transformed into amphibolites and are partly granitized. The relative intensity of their deformation and the cross-cuttings make it possible to determine their relative age. Unaltered diabase represents the younger generation. In between the different periods of dike activity systems of aplites and pegmatites were formed. The presence of several generations of basic dikes in the granitic rocks makes it possible to single out various phases of deformation, each distinct in time and characterized by its peculiar style of structure, vestiges of which have been preserved by subsequent granitisations.

Several generations of basic dikes have been recognized in different parts of the Bamble area, although in some parts the oldest have disappeared due to granitisation. Some miles east of our observation point, near Portør, a late migmatisation has obliterated the oldest traces, and tends to replace al! rocks by homogeneous potassic granite.