Smaland lithotectonic unit dominated by Paleoproterozoic (1.8 Ga) syn-orogenic magmatism, Svecokarelian Orogen

The Smaland lithotectonic unit in the 2.0-1.8 Ga Svecokarelian orogen, southeastern Sweden, is dominated by a c. 1.81-1.77 Ga alkali-calcic magmatic suite (the Transscandinavian Igneous Belt or TIB-1). At least in its central part, the TIB-1 suite was deposited on, or emplaced into, c. 1.83-1.82 Ga calc-alkaline magmatic rocks with base metal sulphide mineralization and siliciclastic sedimentary rocks (the Oskarshamn-Jonkoping Belt). Ductile deformation and metamorphism under low- to medium-grade conditions affected the Oskarshamn-Jonkoping Belt prior to c. 1.81 Ga. Both suites were subsequently affected by low-grade ductile deformation, mainly along steeply dipping, east-west to NW-SE shear zones with dip-slip and dextral strike-slip displacement. Sinistral strike-slip NE-SW zones are also present. In the northern part of the lithotectonic unit, 1.9 Ga magmatic rocks, c. 1.87-1.81 Ga siliciclastic sedimentary rocks and basalt, and c. 1.86-1.85 Ga granite show fabric development, folding along steep NW-SE axial surfaces and medium- or high-grade metamorphism prior to c. 1.81 Ga and, at least partly, at c. 1.86-1.85 Ga; base metal sulphide, Fe oxide and U or U-REE mineralizations also occur. Magmatism and siliciclastic sedimentation along an active continental margin associated with subduction-related, accretionary tectonic processes is inferred over about 100 million years.