Abstract The 1.1–0.9 Ga Sveconorwegian orogen in southwestern Scandinavia belongs to the global system of mountain belts established during the assembly of the supercontinent Rodinia. An overall north–south structural trend and five lithotectonic units bounded by crustal-scale shear zones characterize this orogen. In Sweden, the Eastern Segment abuts the orogen's cratonic foreland eastwards and is separated from the Idefjorden terrane westwards by a ductile shear zone, up to 5 km thick, displaying a sinistral transpressive component. These two lithotectonic units differ on the basis of their pre-Sveconorwegian accretionary tectonic evolution, and the timing of Sveconorwegian high-pressure metamorphism, anatexis and polyphase deformation. High-pressure granulites and migmatites formed at c. 1.05–1.02 Ga in the Idefjorden terrane; eclogites, high-pressure granulites and migmatites at c. 0.99–0.95 Ga in the Eastern Segment. Magmatic activity and crustal extension progressed westwards at c. 0.98–0.92 Ga. Prior to or at 0.93–0.91 Ga, greenschist facies shear deformation with top-to-the-foreland movement affected the frontal part of the orogen. Geodynamic uncertainties concern the affinity of the Idefjorden terrane relative to Fennoscandia (Baltica), the character of the Sveconorwegian orogenesis, and the contiguous or non-contiguous nature of the erosional fronts of the late Mesoproterozoic–early Neoproterozoic orogens in Sweden and Canada.

Abstract Crust generated during an accretionary orogeny at 1.66–1.52 Ga (Gothian), and later during crustal extension at c. 1.51–1.49, c. 1.46, c. 1.34–1.30 Ga and after c. 1.33 Ga, dominate the Idefjorden terrane. Metamorphism under greenschist to, locally, high-pressure granulite facies, emplacement of syn-orogenic pegmatite and granite, and polyphase deformation followed at 1.05–1.02 Ga (Agder tectonothermal phase, Sveconorwegian orogeny). Sinistral transpressive deformation, including foreland-directed thrusting, preceded top-to-the-west movement and large-scale open folding along north–south axial trends during the younger orogeny. Crustal extension with emplacement of dolerite and lamprophyre dykes, norite–anorthosite, and a batholithic granite took place at c. 0.95–0.92 Ga (Dalane phase, Sveconorwegian orogeny). Ductile shear zones divide the Idefjorden terrane into segments distinguished by the character of the Gothian crustal component. Orthogneisses with c. 1.66 and c. 1.63–1.59 Ga protoliths occur in the Median segment; c. 1.59–1.52 Ga gneissic intrusive rocks and 1.6 Ga paragneisses with relicts of Gothian deformation and migmatization at c. 1.59 Ga and at c. 1.56–1.55 Ga occur in the Western segment. Mineral resources include stratabound Cu–Fe sulphides hosted by sandstone deposited after c. 1.33 Ga, and polymetallic quartz vein mineralization locally containing Au.