Polyphase (1.6-1.5 and 1.1-1.0 Ga) deformation and metamorphism of Proterozoic (1.7-1.1 Ga) continental crust, Idefjorden Terrane, Sveconorwegian Orogen

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.