Structural and magmatic segmentation of the Tertiary East Greenland Volcanic Rifted Margin

Abstract

The Tertiary East Greenland Volcanic Rifted Margin is characterized by massive magmatic construction that produced a distinctive crustal architecture including: (1) a thick pile of flood basalts continuing offshore as seismically imaged ‘seaward-dipping reflector sequences’; (2) an extensive margin-parallel mafic dyke swarm; and (3) shallow crustal gabbroic plutons and deeper crustal ‘underplated’ material. These igneous units developed in the framework of an asymmetrical, crustal-scale fold, or ‘flexure’, that accommodated major subsidence along the continent-ocean transition. Extensive exposures along the margin reveal that the flexure and associated igneous structures define rift segments separated by various types of structural discontinuities. First-order segments occur between major triple-rift junctions as at Kangerlussuaq. At an intermediate scale, second-order accommodation zones bound margin segments c. 100 km in length with long-lived structural and/or magmatic expressions. Third-order discontinuities, spaced at tens of kilometres, correspond to smaller accommodation zones at abrupt along-strike changes fault or magmatic structures. Outcrop-scale transfer and transform faults occur at still smaller scales. Some of the larger accommodation zones appear to be related to pre-existing Precambrian structures and may have helped localize relatively late, post-flexure alkalic intrusions. The style of segmentation provides a link between similar segmentation patterns in continental rifts and mid-ocean ridge spreading centres that persist long after continental separation.

The onset of the North Atlantic Igneous Province in a rifting perspective

“…On the one hand, Larsen & Marcussen (1992) Only parts of this extensive area have been investigated in detail, but the close proximity in the Early Palaeogene suggest that these two margins perhaps shared some magmatic centres prior to the sea-floor spreading in the region (Figs 2, 3). Locations for some possible triple junctions in this region in Early Palaeogene times have been implied previously by Burke & Dewey (1973), Bull & Masson (1996), Karson & Brooks (1999), Nielsen, Larsen & Hopper (2002) and Nielsen, Stephenson & Thomsen (2007), and locations of some separate large magmatic centres and domal uplifts have been recorded by Morgan & Barton (1990), Barton & White (1997), Larsen & Saunders (1998) and Elliot & Parson (2008). A hypothetical SE-trending failed rift arm or transform from a triple junction in the southern parts of the Hatton Bank (Figs 2, 3) would be sub-parallel to the South Hatton Lineament Kimbell et al 2005).…”

“…Callot, Geoffroy & Brun, 2002). The locations of hypothetical triple junctions at the CE Greenland margin have been estimated from Early Palaeogene magmatism and uplifts in the area (Larsen & Watt, 1985;Nielsen, 1987;Mathiesen, Bidstrup & Christiansen, 2000;Callot, Geoffroy & Brun, 2002;Peate, Larsen & Lesher, 2003) and from triple junction localities as suggested by Burke & Dewey (1973); Karson & Brooks (1999) and Tegner et al (2008). This vast area was characterized by Early Palaeogene episodic igneous activity and frequent migration of magmatic centres (Larsen & Watt, 1985;Peate, Larsen & Lesher, 2003), and at least three separate rifting events have been recorded for this region, some of which occurred far inland (Nielsen, 1987;Olesen et al 2007).…”

Multistage Cretaceous magmatism in the northern coastal region of Ellesmere Island and its relation to the formation of Alpha Ridge – evidence from aeromagnetic, geochemical and geochronological data

“…Pearya succession 2 is exposed north of succession 1 on Wootton Peninsula, but south of succession 1 east of Yelverton Bay. This is probably a consequence of a segmentation of the northern margin of Ellesmere Island, as described for the magma-rich rifted margin of central East Greenland (Karson & Brooks, 1999). During and after the emplacement of the rhyodacitic rocks, intrusion of mafic dykes occurred east of Yelverton Bay, but with a change towards a more transitional composition.…”

“…The Yelverton Bay area (close to the Alpha Ridge of the Amerasia Basin) shows some characteristic features, which are known from magma-rich rifted (volcanic) margins worldwide (e.g., Menzies et al, 2002) and from central East Greenland (e.g., Karson & Brooks, 1999;Tegner et al, 2008) Our interpretation of the Yelverton Bay area as a magmarich rifted margin coincides with the tectonic model from Funck et al (2011) in which the Alpha-Mendeleev Ridge was formed by seafloor-spreading parallel to the Canadian Polar margin (the Iceland model). A discussion about the involvement of a mantle plume that is postulated by Funck et al (2011) and many other authors is out of scope of this paper.…”

Crustal accretion of thick mafic crust in Iceland: implications for volcanic rifted margins

“…Later dikes cut the dipping ones, demonstrating that the rotation and intrusion were broadly synchronous. Near the coast the dike density increases to nearly 100% in a sheeted dike complex marking the continent-ocean transition (Karson and Brooks 1999;Klausen and Larsen 2002;Nielsen 1978;Nielsen and Brooks 1981). Offshore, lavas and SDRs overlie mafic crust ϳ30 km thick.…”