Evolution structurale de la region Nisser - Vråvatn (Norvege meredionale). (The precambrian rocks of the Telemark area in south central Norway no. VIII. Strucutral development of the Nisser-Vråvatn region.)
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Tectonic and petrographic studies of the Precambrian rocks in the Nisser-Vråvatn region of Telemark have led to the recognition of the following principal features: (1) The basement of the \"Telemark suite\" does not appear in the studied region; it seems that all the migmatites are products of granitization of supracrustal rocks (acid lavas, basic lavas and quartzitic sediments). (2) Three phases of folding have been demonstrated: B1, B2, B3. The phase B1 is synschistose and isoclinal. (3) A later granitic remobilisation occurs in the shear zones of B2. It is accompanied by the \"mise en place\" of molybdenum-rich pegmatites. (4) The last folding B3 disorientate former structures, in such a way that the lineations L2 associated with B2 are deformed following a plane \"locus of L2\". (4) The tectonic axis \"a\" of the last folding (B3) is vertical. (5) The angle between the tectonic axis \"a\" of B3 and the surfaces which were refolded was variavle, which explains the different developments of B2 and B3. (6) A consequence of the three phases of folding was the formation of domes and basins. (7) In one of these basins, \"the Vrådal basin\", there was a \"mise en place\" of a microdioritic complex and of Exogenous material filling the fractures around the basin.