The 616 Ma Old Egersund Basaltic Dike Swarm, Sw Norway, and Late Neoproterozoic Opening of the Iapetus Ocean

Abstract

The Egersund dike swarm of SW Norway is made up of 11 basaltic dikes trending ESE-WNW. Two groups are defined: porphyritic dikes with bytownite phenocrysts of tholeiitic affinity and aphyric dikes of tholeiitic to alkaline affinity. Baddeleyite in the most alkaline dike gives a U-Pb intrusive age of 616 Ϯ 3 Ma. The swarm is parallel to the Neoproterozoic southwestern (present-day orientation) Tornquist margin of Baltica. It is coeval with the Long Range swarm of Labrador which is parallel to the southeastern proto-Appalachian margin of Laurentia. Both swarms are related to rifting that resulted in the opening of Iapetus ocean. Chronocorrelation of Neoproterozoic rift-related magmatic suites in western Baltica and eastern Laurentia suggests diachronic opening of Iapetan oceanic basins at ca. 610 Ma along the northwestern Baltoscandian margin of Baltica and at ca. 550 Ma along the proto-Appalachian margin of Laurentia and Tornquist margin of Baltica.

Evidence of Late Ediacaran Hyperextension of the Laurentian Iapetan Margin in the Birchy Complex, Baie Verte Peninsula, Northwest Newfoundland: Implications for the Opening of Iapetus, Formation of Peri-Laurentian Microcontinents and Taconic – Grampian Orogenesis

“…However, available data suggest that rifting progressed from northeast to southwest in present coordinates, being the oldest in Baltica (Bingen et al 1998) and becoming younger in Scotland (e.g. Leslie et al 2008) and the Appalachians (van Staal et al 1998;Burton and Southworth 2010).…”

Detrital zircon fingerprint of the Proto-Andes: Evidence for a Neoproterozoic active margin?

“…Bond et al, 1984;Williams and Hiscott, 1987), and the voluminous riftrelated magmatism which lasted from ∼620 Ma to 550 Ma (e.g. Kamo et al, 1989;Bingen et al, 1998;Cawood et al, 2001;Kinny et al, 2003). Cawood et al (2001) invoked a multistage rift history that involved an initial separation of Laurentia from the west Gondwana cratons at ca.…”

Baltica in the Cryogenian, 850–630 Ma

“…Paleo-to Mesoproterozoic basement (e.g. Bingen et al, 1998;ValverdeVaquero et al, 2000;Mansfeld, 2001;Krzeminska et al, 2005) of the EEC is overprinted by later orogeny at ca. 1.5-1.4 Ga (the Gothian or Danopolonian orogeny) and/or at ca.…”

“…Voluminous rift-related igneous activity, including large ultramafic/mafic magmatism (e.g. the Seiland Igneous Province) and extensive, margin-parallel dike swarms, intrudes the Seve-Kalak Superterrane (Andréasson, 1994;Bingen et al, 1998;Roberts et al, 2006). Polyphase deformation and partial migmatisation precludes reliable observations of possible lateral facies changes, particularly within the Seve Nappe Complex.…”