New petro-paleomagnetic data of Kandalaksha and Onega Bay Islands in the White Sea

We have studied the AMS of metamorphic rocks (gneiss, granitoids, dykes) and soft sediments (mainly marine sediments or reworked diamicton) from the Kandalaksha and Onega Bay’s Islands of the White sea. The objects of research are located within the White sea mobile belt, represented by large tectonic nappes.

The magnetic susceptibility in soft sediment samples ranges from 78.6 E-6 to 1525E-6 (Km), and the degree (P) from 1.8% to 4.1%. Ellipsoids have a predominantly flattened type, such a distribution of AMS is typical for sedimentary rocks. At the same time, in a number of samples (from the Islands of Joker, Ipanchinikha and Olenevsky), the maximum axis is directed in a North-Westerly direction, which may indicate the flow direction. This is especially evident in flattened-triaxial ellipsoids (T=0.2-0.3). Values that have a T greater than 0.5 have a predominantly northerly direction and the orientation of minerals of the magnetic fraction and the direction of paleoflow is less pronounced.

The study of the anisotropy of the magnetic susceptibility of the Archean complexes composing the Islands of the Kandalaksha Bay of the White sea showed a high magnetic susceptibility-5E-6-1E-3 (Km), which confirms the change in the petrographic composition of gneiss. The degree of anisotropy (P) is 9% on average. It was found that the distribution of the main axes of the magnetic susceptibility ellipsoid coincides with shale and banding in the root outlets, while the maximum axis of the ellipsoid coincides with the West-North-West stretch of the regional fault. In the Onega Bay we sampled paleoproerozoic dykes, and there are AMS is coincided as contacts of studied dykes.

We done alternating field and thermal demagnetization of pilot collection which contains samples from all studied complexes. And it gives us not good results because of bad paleomagnetic record. Most of samples contain only low coercive or low temperature components and it mainly has modern direction.