| dc.description.abstract | The tectonic evolution of the Late Mesoproterozoic Sveconorwegian Province has traditionally been considered to reflect continent-continent collision, which has been correlated with the Grenville Province in Canada. The metamorphic evolution of southwestern Norway has been described as a regional high-grade metamorphic event that took place between 1035 and 970 Ma, as a result of orogenic thickening, followed by a contact-metamorphic event at c. 930 Ma due to the emplacement of the Rogaland Igneous Complex (RIC). The continent-continent collision model has, however, been questioned based on extensive mapping and new geochronology data from the Sveconorwegian Province. A long-lived accretionary margin, undergoing periodic compression and extension has recently been suggested to better explain the metamorphic and magmatic evolution of the Sveconorwegian Province. This study evaluates the two tectonic models for the Sveconorwegian Province by detailed geological mapping and U-Pb geochronology from Lysefjorden, Gyadalen and the Kvås-Konsmo area. Undeformed to weakly deformed porphyritic granites and metamorphosed diorites display zircon ages ranging from c. 1050 Ma to 1030 Ma. These ages are compatible with the previously recorded magmatic activity in the Sirdal Magmatic Belt (SMB). The SMB is a recently discovered granitic batholith (c. 1060-1020 Ma). In this study a diorite from the Kvås-Konsmo area was analysed and yield a crystallization age of 991 ± 11 Ma, which is younger than the SMB. Zircon geochronological data from Lysefjorden, Gyadalen and the Kvås-Konsmo area indicate that partial melting and metamorphism was coeval with and possibly related to the emplacement of the SMB. Monazite ages from the Kvås metapelite range from c. 980 to 900 Ma, and it is suggested that these ages reflect heating related to long-lived voluminous magmatism. In light of the new field and geochronological data it appears that the metamorphic and magmatic evolution of southwestern Norway cannot satisfactorily be explained by crustal thickening and radioactive self-heating as previously suggested. It is therefore proposed that the zircon and monazite ages are a result of magmatically driven UH/UHT metamorphism. And it is proposed that voluminous basaltic underplating can have contributed to the heat that was necessary to cause high-grade metamorphism reflecting long-lived arc magmatism. To be able to explain different pressure estimates in the region, a dome structure formed under the orogen is suggested. The RIC may have formed the core of this dome structure. | eng |