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.

Abstract This paper summarizes the main geochronological features of the Caledonian nappes in southern Norway, discusses their similarities and differences, and reports new U–Pb isotope dilution thermal ionization mass spectrometry data. The latter include ages of 1670 Ma for orthogneiss from the Upper Finse Nappe, 1500, 1250 and 950 Ma for intrusive rocks from the Hallingskarvet Nappe, and 1037 and 997 Ma for volcanic units from the Suldal and Lower Finse nappes. The Caledonian nappes can be subdivided into units formed at 1700–1600 Ma, having an affinity with Gothian crust, and units formed at about 1500 Ma, correlating with Telemarkian crust. A Sveconorwegian tectonometamorphic overprint is ubiquitous, but with large differences in the intensity and relative timing of the overprint. Some complexes (such as Kvitenut–Dyrskard) were affected at around 1000 Ma and others (such as Jotun and Lindås) between 970 and 930 Ma. There is also considerable variety in the Caledonian effects. Ordovician events affected some nappes (Jæren, Revsegg), thought to be of exotic origin, while Silurian and Devonian events of variable intensity are observed in all nappes. The emerging patterns offer the basis for a qualitative discussion of the provenance of the nappes that can eventually be combined with quantitative structural criteria to reconstruct pre-Caledonian palaeogeographies.

Abstract The Espedalen Nappe is located in the east of the Jotun–Valdres Nappe Complex in southern Norway. Its main component, the Espedalen Complex, consists of an early suite of jotunite, charnockite and augengneiss, a main anorthosite–ultramafite–norite suite, and a late gabbronorite suite. Mafic dykes and lamprophyres cut the complex, some being feeders to the Stylskampen mafic to felsic suite at the western margin of the complex. The complex hosts Ni–Cu mineralizations which were mined in past centuries. Two crystalline outliers occur at Ormtjernkampen and Røssjøkollen further south. Caledonian convergence thrust the nappe on to Early Palaeozoic sedimentary rocks. Rocks of the Espedalen Complex are covered and/or tectonically interleaved with Late Precambrian conglomerates and arkoses of the Valdres Group. Dating of zircon and titanite by ID-TIMS U–Pb indicates formation of the complex at 1520–1510 Ma, followed by deformation and metamorphism between 1050 and 950 Ma during the Sveconorwegian orogeny, before the eventual translation during the Caledonian orogeny. These data indicate an affinity of the nappe with Telemarkian crust in the autochthonous Baltic basement, in contrast to the rocks of the overlying Jotun Complex which correlate instead to Gothian crust formed between 1600 and 1700 Ma.