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Articles |
1 Tectonics Special Research Centre, School of Earth and Geographical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, 6009, WA, Australia
2 Present address: School of GeoSciences, The University of Edinburgh, Grant Institute, The King's Buildings, West Mains Road, Edinburgh EH9 3JW, UK (e-mail: Sergei.Pisarevsky{at}ed.ac.uk)
3 Department of Earth Sciences St. Francis Xavier University, Antigonish, Nova Scotia, B2G 2W, Canada
4 Continental Evolution Research Group, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, SA 5005, Australia
We present two alternative sets of global palaeogeographical reconstructions for the time interval 615–530 Ma using competing high and low-latitude palaeomagnetic data subsets for Laurentia in conjunction with geological data. Both models demonstrate a genetic relationship between the collisional events associated with the assembly of Gondwana and the extensional events related to the opening of the Tornquist Sea, the eastern Iapetus Ocean (600–550 Ma), and the western Iapetus Ocean (after 550 Ma), forming a three-arm rift between Laurentia, Baltica, and Gondwana. The extensional events are probably plume-related, which is indicated in the reconstructions by voluminous mafic magmatism along the margins of palaeo-continents. The low-latitude model requires a single plume event, whereas the high-latitude model needs at least three discrete plumes. Coeval collisions of large continental masses during the assembly of Gondwana, as well as slab pull from subduction zones associated with those collisions, could have caused upper plate extension resulting in the rifted arm that developed into the eastern Iapetus Ocean and Tornquist Sea but retarded development of the western Iapetus Ocean. As a result, the eastern Iapetus Ocean and the Tornquist Sea opened before the western Iapetus Ocean.
