NJG85-1/2-07
2005
Timing of continental building in the Sveconorwegian orogen, SW Scandinavia
85
1, 2
pp. 87-116
82-92394-21-4

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 Sveconorwegian 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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