Svecofennian Orogen of the Fennoscandian Shield: Compositional and isotopic zoning and its tectonic interpretation

Abstract

Endogenic events in the form of intrusive activity and regional metamorphism developed asynchronously in various parts in the Svecofennian Orogen of Fennoscandia. The Early and Late Svecofennian stages of regional high-temperature metamorphism and related plutonism are distinguished from isotopic evidence. The composition, structural features, and asynchronous peaks of endogenic activity within the orogen indicate that at least two zones (inner and outer) should be distinguished in the Svecofennides. The lateral heterogeneity of the orogen in present-day coordinates is traced southward from the margin of the Archean craton. The conjugation zone of the Svecofennian Orogen and the Archean Karelian Craton is characterized by transition from negative to positive eNd (1.9 Ga) values as evidence for a decreased contribution of Archean crustal material to the source of Proterozoic granitoids from the north toward the Proterozoic domain in the south. With allowance for lateral compositional and isotopic heterogeneity of the Svecofennian Orogen and asynchronous culmination of endogenic events in different parts of this orogen, a new scheme of tectonic regionalization has been proposed.