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Abstract
Recent U-Pb zircon dating on the Småland-Värmland granites and porphyries suggests that these rocks formed 1760–1840 Ma ago, about 50 to 100 Ma earlier than indicated by previous Rb-Sr age determinations. This would make the ‘postorogenic’ granites of the Småland-Värmland belt similar in age to the ‘lateorogenic’ granites of the Svecokarelian province. A tectonic model is proposed where the Småland-Värmland belt originated in a tensional regime, possibly an ensialic continental rift, penecontemporaneous with folding, migmatitization and formation of ‘lateorogenic’ anatectic granites in a compressional regime further to the northeast. The relationship between the Småland-Värmland belt and the Southwest Swedish gneiss province remains uncertain, and may partly have been obscured by movements along the Protogine zone.
