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Correlation of supracrustal sequences and origin of terranes in the Sveconorwegian orogen of SW Scandinavia: SIMS data on zircon in clastic metasediments

2001; Elsevier BV; Volume: 108; Issue: 3-4 Linguagem: Inglês

10.1016/s0301-9268(01)00133-4

1872-7433

Bernard Bingen,

Geochemistry and Geologic Mapping

Ion probe U–Pb data on detrital zircons were acquired in five pre-Sveconorwegian clastic metasedimentary units in the Sveconorwegian orogen in S Norway. Turbidite-type sediments in the Veme complex (Begna sector, west of the Oslo rift) display zircons between 1.67 and 1.53 Ga (9 grains). This complex is interpreted as a westward, younger extension of the Stora Le–Marstrand metasedimentary belt (≤1.58 Ga) of the Idefjorden terrane (east of the Oslo rift). The belt formed in an outboard setting, and the detritus in the sediments was probably mainly derived from subduction-related complexes exposed in the Idefjorden terrane. To the west, a quartzite of the Hallingdal complex in the Telemark sector has zircon populations at 3.13–2.68 and 2.03–1.71 Ga (34 grains). It was deposited between 1.7 and 1.5 Ga and attests the presence of differentiated continental crust older than 1.5 Ga in S Norway. Two samples of the Hettefjorden and Festningsnutan Groups from the Hardangervidda plateau have zircon populations at 3.25–2.42 and 2.03–1.54 Ga (47 grains). The 1.90–1.85 Ga frequency maximum of the age distribution in these three epicontinental sediments corresponds with the peak of Svecofennian magmatic activity in central Sweden, and to the age of the main zircon populations in late-Svecofennian sediments. This is an indication of a Fennoscandian origin for the Telemark–Bamble and Rogaland–Hardangervidda terranes, at the margin of the Svecofennian domain; alternative exotic provenances are possible. A quartzite sample of the Modum complex in the Kongsberg sector displays 2.07–1.48 Ga Proterozoic zircon populations (28 grains) and minor Archaean populations. The Modum complex represents, probably together with the Kragerø complex in the Bamble sector and the Seljord Group in the Telemark sector, parts of a quartzite-rich epicontinental cover deposited after 1.48 Ga on the Telemark–Bamble terrane. The juxtaposition of the Telemark–Bamble and Rogaland–Hardangervidda terranes with the subduction-related Idefjorden terrane, can be explained by a transpressive translation of these terranes at the margin of the Fennoscandian shield during the Sveconorwegian orogeny. Sveconorwegian sinistral strike-slip shearing probably took place along an amphibolite-facies banded gneiss unit situated at the boundary.