Magnetic properties of the Alnön Complex

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Abstract
The plutonic rocks, sövite ring dykes and alnöite dykes belonging to the (Cambrian) Alnön Complex have been analysed for palaeomagnetic study. Total NRM's residing in magnetite and pyrrhotite are locally very high in the plutonic facies and variable in the sövite dykes; all the alkaline phases have NRM's dominated by low coercivity components. Alternating field demagnetisation isolates a range of remanence directions, but a principal mean of D = 107°, I = 2°(α95 = 9°) in the bulk of the sövite and alnöite dykes is defined by both polarities and confirmed by thermal cleaning. A subsidiary direction of D =350°, I = 15° (α95 = 11°) is recognised predominantly in the plutonic rocks. The data contribute to the sparse Cambrian palaeomagnetic record from the Fennoscandian Shield and support earlier suggestions of large apparent polar wander motion in Cambrian times.