Remagnetisation and magnetic refraction in Proterozoic dykes from central Scandinavia during Caledonian deformation

Mafic dykes, related to the Central Scandinavian Dolerite Group, changed th eir geometry during the Caledonian orogeny from flat-lying bodies in the Au tochthon to steeply inclined in the thrusted and stacked Lower Allochthon u nits. During tectonic transport remagnetisation occured and the post-Jotnia n paleomagnetic signature was completely obliterated. In the Bangonaive win dow this remagnetisation occurred at a deeper crustal level probably during metamorphism and deformation under amphibolite-facies conditions, while in the Borgefjell window it was caused by alteration in a more shallow crusta l level. In both tectonic windows the remanence direction is influenced by the structure, and in the strongly anisotropic samples of the Bangonaive wi ndow a distinct refraction of the remanence direction (up to 15 degrees) to wards the magnetic lineation is observed. (C) 2000 Elsevier Science Ltd. Al l rights reserved.