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TitleStructural evolution of the rifted margin off northern Labrador: the role of hyperextension and magmatism
AuthorKeen, C E; Dickie, K; Dafoe, L TORCID logo
SourceTectonics vol. 37, issue 7, 2018 p. 1955-1972, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20170239
PublisherAmerican Geophysical Union (AGU)
Mediapaper; on-line; digital
File formatpdf; html
ProvinceNewfoundland and Labrador; Northern offshore region
NTS14; 15C; 15D; 15E; 15F; 24A; 24H; 24I; 24J; 25A; 25H
AreaLabrador; Labrador Sea
Lat/Long WENS -65.0000 -56.0000 61.3333 56.7500
Subjectsstructural geology; tectonics; geophysics; crustal structure; crustal evolution; crustal thickness; continental crust; craton; oceanic crust; mantle; Mohorovicic discontinuity; tectonic history; tectonic setting; plate tectonics; plate margins; rifts; magmatism; alteration; serpentinization; deformation; continental margins; continental shelf; geophysical surveys; seismic reflection surveys; seismic refraction surveys; seismic velocities; gravity surveys; magnetic interpretations; bathymetry; bedrock geology; lithology; igneous rocks; volcanic rocks; basement geology; structural features; faults; escarpments; Paleogene; Eocene; Paleocene; Archean; Labrador Margin; Labrador Shelf; Saglek Basin; Okak Arch; Hopedale Basin; Nain Craton; Torngat Orogen; Churchill Domain; Ungava Fracture Zone; Snorri Fracture Zone; Cartwright Fracture Zone; Greenland Margin; Fylla Structural Complex; Phanerozoic; Cenozoic; Tertiary; Mesozoic; Cretaceous; Precambrian
Illustrationslocation maps; geoscientific sketch maps; seismic reflection profiles; gravity profiles; cross-sections; models; tables
ProgramGEM2: Geo-mapping for Energy and Minerals Baffin Petroleum Systems
Released2018 06 11
AbstractHigh-quality seismic reflection data from the offshore northern Labrador rifted margin allow imaging of the extended and rifted crust both along and across the continental margin and are described in conjunction with available seismic velocity and gravity data. The margin formed within cold, thick cratonic lithosphere. Both Archean continental basement and a discrete, undulating, high-amplitude, deep reflection about 10 km below basement are observed. The deeper reflection can be correlated with the crust-mantle boundary as measured on previous wide-angle seismic data in the region. This reflection, termed here the L-reflection, appears to be the equivalent to other top-mantle detachments found elsewhere on magma-poor rifted margins. However, normal mantle velocities have been observed to lie just below the reflection, suggesting that it may not be related to the formation of weak serpentinized mantle. A high-velocity and density zone occupies the outer shelf seaward of the L-reflection where basement is transparent, which may represent highly mafic crust or serpentinized mantle. A crustal reconstruction of this margin and its conjugate shows marked asymmetry, with a wider zone of crustal thinning on the Greenland margin. These crustal thinning profiles are comparable to those on other conjugate margins within cratonic lithosphere. While some of the attributes of this margin are those of a magma-poor system, at the ocean-continent transition, thick igneous crust created a magma-rich zone in Paleocene time when a hot spot was active in the Davis Strait to the north. Thus, this margin exhibits characteristics of both magma-rich and magma-poor systems.
Summary(Plain Language Summary, not published)
Offshore of northern Labrador, new industry seismic reflection data provides enhanced images of the deep basement structure where the rocks of the continental margin thin and transition into oceanic crust underlying the central part of the Labrador Sea. This transition is important to understand in regional basin studies as it provides tectonic context and age constraints for the overlying sediments and their petroleum potential. Expanding on studies to the south, we outline a zone of possible serpentinized and/or exhumed mantle lying between hyper-extended continental and oceanic crust. We show the seismic characteristics of these zones and briefly discuss the adjacent volcanic margin. The results are compared to the conjugate West Greenland margin and other regions with notable similarities to those off Iberia and Newfoundland.

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