Paleomagnetic studies of rapakivi complexes in the Fennoscandian shield – Implications to the origin of Proterozoic massif-type anorthosite magmatism

• Published in: Precambrian Research
• Main Authors: Salminen, Johanna, Elming, Sten-Åke, Mertanen, Satu, Wang, Chong, Almqvist, Bjarne, Moakhar, Mohsen Oveisy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Uppsala universitet, Geofysik 2021
• Subjects: Paleomagnetism; Massif anorthosites; Rapakivi; Proterozoic; Baltica; Nuna supercontinent; Geology; Geologi; Geophysics; Geofysik; Fennoscandian
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454560; https://doi.org/10.1016/j.precamres.2021.106406

Paleomagnetic studies have been performed on five rapakivi related complexes in Sweden and Finland. Poles of varying quality have been defined and the majority of the similar to 1640-1497 Ma poles are clustering on low latitudinal positions. By combining data from similar to 1500 Ma intrusions a new high-quality pole (Plat: 13 degrees N; Plon: 190 degrees E; A(95): 11 degrees, K: 14) for Baltica has been defined. Tectonic reconstructions, on the basis of the new data and previously published high-quality data, indicate that Baltica experienced stable low latitude to equatorial positions during 1640-1470 Ma, temporally coinciding with globally pronounced rapakivi-anorthosite magmatism. Our study argues against single hotspot source for similar to 1640-1620 Ma, similar to 1590-1520 Ma, and 1470-1410 Ma rapakivianorthosites, but supports a model of large-scale superswell under a stationary low-latitude position of supercontinent Nuna for the origin of rapakivi-anorthosite magmatism. However, a possibility for convergent tectonism as the origin cannot be ruled out.