HR: 1340h
AN: GP33A-0098    [Abstracts]
TI: Paleomagnetism of 935 Ma Mafic Dykes in Southern Sweden : new Implications for the Sveconorwegian Loop
AU: * Pisarevsky, S A
EM: spisarevsky@tsrc.uwa.edu.au
AF: Tectonics Special Research Centre, University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 Australia
AU: Bylund, G
EM: Goran.Bylund@geol.lu.se
AF: Department of Geology, GeoBiosphere Science Centre, Lund University, Salvegatan 12, Lund, 223 62 Sweden
AB: Early Neoproterozoic mafic intrusions are widespread in southern Sweden and southern Norway, and have been subjected to intensive palaeomagnetic studies. The majority are from dolerite dykes of the Protogine Zone and the Blekinge-Dalarna Dolerites in southern Sweden. They are good quality results, but were poorly dated until recently - ages of 1000-880 Ma were estimated by Sm-Nd and Rb-Sr methods. Several recent publications provide new precise ages for some mafic intrusions in southern Sweden between ~915 and ~960 Ma. In particular, Hellström et al. (2004) reported a new U-Pb baddeleyite age of 935 ± 3 Ma for the Tuve dyke in the Göteborg area. A preliminary palaeomagnetic study of ten samples from this dyke was reported by Abrahamsen (1974). Despite its good quality, this result has not usually been included in plate tectonic reconstructions due to imprecise dating of the dykes (until recently) and the small number of samples. The Slussen dyke of the same swarm was also studied palaeomagnetically in the Bredfjället area ~ 60 km north of Göteborg by us. New palaeomagnetic results for the 935 Ma Göteborg-Slussen mafic dykes in southern Sweden provide a well-dated high-quality palaeomagnetic pole for early Neoproterozoic Baltica. New U-Pb geochronological data for several palaeomagnetically studied mafic intrusions yield three additional well-dated palaeopoles and one virtual geomagnetic pole (VGP). This set of dated poles suggests minimal drift of Baltica in moderate latitudes between ~ 965 and 915 Ma. They also support the hypothesis of a post-900 Ma regional remagnetisation event in SW Sweden and SW Norway. The positions of three distinct clusters of ~1100 - 850 Ma palaeopoles suggest a clockwise time progression of the Baltica apparent polar wander path (the Sveconorwegian Loop) during this time interval. New well-dated palaeomagnetic poles for ~970 - 900 Ma from Laurentia are required to verify the palaeogeographic reconstructions of Baltica and Laurentia.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005