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TitreCrustal structure of the Labrador Sea conjugate margin and implications for the formation of nonvolcanic continental margins
AuteurChian, D; Louden, K E; Reid, I
SourceJournal of Geophysical Research, Solid Earth vol. 100, no. B12, 1995 p. 24,239-24,253, (Accès ouvert)
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 55394
Documentpublication en série
Mediapapier; en ligne; numérique
ProvinceRégion extracotière de l'est
Sujetsdonnées sismiques; profils sismiques marins; levés sismiques marins; marges continentales, atlantique; marges continentales; études de la croûte; croûte océanique; tectonique; géologie générale; géologie marine
Illustrationsseismic reflection profiles; location maps; magnetic profiles
ProgrammeCRSNG Conseil de recherches en sciences naturelles et en génie du Canada
ProgrammeDalhousie University, Graduate Scholarship Program
Diffusé2012 09 20
Résumé(disponible en anglais seulement)
Wide-angle seismic studies have determined the detailed velocity structure along a 350-km-long profile across the Labrador margin. Combination of this model with a previously published cross section for the southwestern Greenland margin constitutes the first combined conjugate margin study based on seismic velocity structure. The results indicate three distinct zones across the Labrador margin, similar to the structure of the conjugate Greenland margin. Zone 1 represents 27 to 30-km-thick continental crust thinning gradually seaward over ~100 km distance. Farther seaward, zone 2 is 70–80 km wide, characterized by a distinct lower crust, 4–5 km thick, in which velocity increases with depth from 6.4 to 7.7 km/s. Interpretation for this lower crustal block favors an origin by serpentinized peridotite rather than by magmatic under-plating. Zone 3 represents two-layered, normal oceanic crust. The cross sections from both margins are reconstructed to an early drift stage at Chron 27. This demonstrates that the serpentinites in zone 2 are symmetrically distributed between previous identifications of Chrons 31 and 33 on both margins. Zone 1 shows a marked asymmetry, with a gradual thinning of continental crust off Labrador contrasted with a rapid thinning off Greenland. The abundant serpentinization of upper mantle peridotite in zone 2 and the asymmetric shape of zone 1 are both probably related to a very slow rate of continental rifting which produced little if any melt.