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Previous studies have postulated that Laurentia and Baltica formed part of a supercontinent at 2.45 Ga. New paleomagnetic studies from the Archean Karelian craton of the Fennoscandian shield can shed light on these Paleoproterozoic reconstruction models of Laurentia and Baltica. This study presents the paleomagnetic results from three well-preserved Neoarchean sites in the Karelian craton. Two of the sites are characterized by rocks that have retained their original Archean magnetic signatures due to the anhydrous granulite-grade mineralogy. The third site is spatially distant from the 1.9-1.8 Ga Svecofennian orogenic front.
The two oldest data are obtained from 2.73 Ga sanukitoids in Lieksa, eastern Finland and from the 2.69 Ga enderbites in Varpaisjärvi, central Finland. The final amalgamation of the Archean Karelian blocks was associated with high-grade metamorphism at ca. 2.69-2.63 Ga, therefore both areas likely record the same cooling history. A steep upwards-pointing remanence was obtained in Lieksa and a steep downwards-pointing remanence was obtained in Varpaisjärvi. The magnetizations are interpreted as 'primary' Archean directions in both areas based on the presence of undeformed cross-cutting vertical-subvertical Paleoproterozic dykes, the absence of Svecofennian overprinting, and rock magnetic studies which suggest that the remanence is carried by SD/PSD magnetite grains associated with Archean-aged alteration. The third site is from the Vodlozero terrane in Russian Karelia, which escaped Svecofennian overprinting. A gabbronorite dyke (2608 ± 56 Ma) and surrounding gneisses record a low inclination remanence direction acquired during the last metamorphic event at ca. 2.55 Ga.
The 2.69-2.63 Ga paleomagnetic data from Karelia place the craton at high paleolatitudes, consistent with the high paleolatitude of the Superior province of Laurentia. The Laurentian reconstruction is based on the most reliable data from 2.69-2.67 Ga formations in the Global Paleomagnetic Database (GPDB). At 2.55 Ga the Karelian craton was located at the equator and the reconstruction with the Superior craton places Karelia to the south of Superior with a latitudinal difference of ca. 30°. This 2.55 Ga reconstruction is in close agreement with the reconstruction at 2.45 Ga, which is based on paleomagnetic data from the Matachewan dykes of Superior and Burakovka dykes of Karelia. Between 2.55 and 2.45 Ga the cratons maintained their relative positions and drifted latitudinally about 30°. The maximum error limits for the poles at 2.55 Ga and 2.45 Ga places a 15° latitudinal difference between the two cratons. If the 2.55 Ga reconstruction is valid, the 2.45 Ga reconstruction of opposite polarity that places Karelia to the NE of Superior cannot be possible.
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