Palaeoproterozoic (2.0-1.95Â Ga) pre-orogenic supracrustal sequences in the West Troms Basement Complex, North Norway

New U-Pb-data from two supracrustal belts enclosed in Archaean crust in the West Troms Basement Complex (WTBC) of North Norway document the presence of volcanic, subvolcanic and sedimentary rocks formed in the pre-orogenic period of extension and basin formation after 2.0 Ga. The Mjelde-Skorelvvatn belt of highly deformed supracrustal rocks is dominated by mafic metavolcanic rocks, including metagabbro dated by zircon at 1992 ± 2 Ma. These mafic rocks are temporal correlatives of a number of occurrences in Fennoscandia and Laurentia such as the Pilguyarvi unit in the Pechenga structure in the Kola peninsula and the Purtuniq unit in northern Labrador. The Torsnes belt contains siliciclastic and metavolcanic mafic rocks unconformably overlying Neoarchaean crust. The indicated maximum deposition age of the Torsnes belt is given by the age of 1970 ± 14 Ma for the youngest detrital zircon. The absence of 1.95 Ga and younger detrital zircons, which are abundant in Svecofennian siliciclastic sequences in Fennoscandia, suggests that the Torsnes belt is a distinct pre-orogenic deposit, and we interpret it as a marginal continental or intracontinental siliciclastic-volcanic basin. The new data from the WTBC can be placed in the context of continental divergence and sea-floor formation in the period between 2.0 Ga and the commencement of orogeny in Fennoscandia and Laurentia at 1.92 Ga.