UPb and RbSr geochronology of the eastern part of the south Rogaland igneous complex, southern Norway

Abstract

The successive intrusive events in the eastern part of the south Rogaland anorthosito-mangeritic complex have been dated by the UPb method applied to zircon, sphene, monazite, uraninite and accessorily by the RbSr whole rock isochron method. The whole magmatic activity in that part of the complex takes place in a short time interval: between 955 m.y., the intrusion age of the Bjerkrem-Sogndal layered norites, and 910 m.y., the emplacement age of a pergmatite in the Lyngdal granodiorite. The UPb geochronological data are consistent with field and petrological data on origin and mutual relations of the intrusives. The RbSr data give incoherent results probably due to open system behaviour in some cases.