Abstract Two lithotectonic units (the Norrbotten and Överkalix units) occur inside the Paleoproterozoic (2.0–1.8 Ga) Svecokarelian orogen in northernmost Sweden. Archean (2.8–2.6 Ga and possibly older) basement, affected by a relict Neoarchean tectonometamorphic event, and early Paleoproterozoic (2.5–2.0 Ga) cover rocks constitute the pre-orogenic components in the orogen that are unique in Sweden. Siliciclastic sedimentary rocks, predominantly felsic volcanic rocks, and both spatially and temporally linked intrusive rock suites, deposited and emplaced at 1.9–1.8 Ga, form the syn-orogenic component. These magmatic suites evolved from magnesian and calc-alkaline to alkali–calcic compositions to ferroan and alkali–calcic varieties in a subduction-related tectonic setting. Apatite–Fe oxide, including the world's two largest underground Fe ore mines (Kiruna and Malmberget), skarn-related Fe oxide, base metal sulphide, and epigenetic Cu–Au and Au deposits occur in the Norrbotten lithotectonic unit. Low- to medium-pressure and variable temperature metamorphic conditions and polyphase Svecokarelian ductile deformation prevailed. The general northwesterly or north-northeasterly structural grain is controlled by ductile shear zones. The Paleotectonic evolution after the Neoarchean involved three stages: (1) intracratonic rifting prior to 2.0 Ga; (2) tectonic juxtaposition of the lithotectonic units during crustal shortening prior to 1.89 Ga; and (3) accretionary tectonic evolution along an active continental margin at 1.9–1.8 Ga.

Abstract Six separate lithotectonic units, referred to from north to south as the Överkalix, Norrbotten, Bothnia–Skellefteå, Ljusdal, Bergslagen and Småland units, are identified inside the western part of the 2.0–1.8 Ga Svecokarelian orogen, Fennoscandian Shield, Sweden. Apart from the boundary between the Norrbotten and Bothnia–Skellefteå lithotectonic units in northern Sweden, which is defined on the basis of a change in crustal basement from Neoarchean (and possibly older) in the NE (Norrbotten) to juvenile Paleoproterozoic crust further south (Bothnia–Skellefteå), all the boundaries are defined by shear zones or combinations of zones that, in places, form broader shear belts up to several tens of kilometres thick. The identification of lithotectonic units provides a necessary foundation for a more detailed synthesis of the tectonic evolution of the 2.0–1.8 Ga orogeny in northern Europe, emphasizing in particular the allochthoneity between most of these units inside this part of the orogen.