Geology and U–Pb geochronology of the Espedalen Complex, southern Norway, and its position in the Caledonian nappe systems

Abstract

AbstractThe 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.