54105 NGT Innmat Nr.1-05
NORWEGIAN JOURNAL OF GEOLOGY Timing of continental building in the Sveconorwegian orogen 87 Timing of continental building in the Sveconorwegian orogen, SW Scandinavia Bernard Bingen, Øyvind Skår, Mogens Marker, Ellen M. O. Sigmond, Øystein Nordgulen, Jomar Ragnhildstveit, Joakim Mansfeld, Robert D. Tucker & Jean-Paul Liégeois Bingen, B., Skår, Ø., Marker, M., Sigmond, E. M. O., Nordgulen, Ø., Ragnhildstveit, J., Mansfeld, J., Tucker, R. D. & Liégeois, J.-P.: Timing of continen- tal building in the Sveconorwegian orogen, SW Scandinavia. Norwegian Journal of Geology, Vol. 85, pp. 87-116. Trondheim 2005. ISSN 029-196X. The timing of continental building in the Sveconorwegian orogen of SW Scandinavia is evaluated with zircon U-Pb geochronology. ID-TIMS, LA-ICPMS and SIMS data are reported for 21 samples of orthogneiss, metarhyolite and metasandstone in S Norway, with emphasis on the Suldal area. The Sveconorwegian orogen is divided into a reworked Fennoscandian 1.80-1.64 Ga parautochthonous segment, the Eastern Segment, and two allochthonous terranes. The Idefjorden terrane is interpreted as a composite 1.66-1.52 Ga arc formed at the margin or near the margin of Fennoscandia. The western terrane, including the Telemark, Hardangervidda, Suldal and Rogaland-Vest Agder sectors, is named Telemarkia. U-Pb zircon data indicate that Telemarkia was built during a short magmatic event between 1.52 and 1.48 Ga, and was located at the margin of a Palaeoproterozoic craton, possibly Fennoscandia. No basement older than 1.5 Ga can be positively identified. In the early stage of the Sveco- norwegian orogeny, Telemarkia collided with the Idefjorden terrane. The Bamble-Kongsberg sector, characterized by a mixed lithology and 1.13-1.10 Ga early-Sveconorwegian high-grade metamorphism, is interpreted as the original collision zone between these terranes.
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