The oceanic crustal structure at the extinct, slow to ultraslow Labrador Sea spreading center

• Published in: Journal of Geophysical Research: Solid Earth
• Main Authors: Delescluse, Matthias, Funck, Thomas, Dehler, Sonya, Louden, Keith, Watremez, Louise
• Other Authors: Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Geological Survey of Denmark and Greenland (GEUS), Bedford Institute of Oceanography, Dalhousie University Halifax, Laboratoire d’Océanologie et de Géosciences (LOG) - UMR 8187 (LOG), Centre National de la Recherche Scientifique (CNRS)-Université du Littoral Côte d'Opale (ULCO)-Université de Lille-Institut national des sciences de l'Univers (INSU - CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; Greenland; Indian; Newfoundland; Labrador Sea
• Online Access: https://hal.archives-ouvertes.fr/hal-02901012; https://hal.archives-ouvertes.fr/hal-02901012/document; https://hal.archives-ouvertes.fr/hal-02901012/file/jgrb51175-1.pdf; https://doi.org/10.1002/2014JB011739

International audience Two seismic refraction lines were acquired along and across the extinct Labrador Sea spreading center during the Seismic Investigations off Greenland, Newfoundland and Labrador 2009 cruise. We derived two P wave velocity models using both forward modeling (RAYINVR) and traveltime tomography inversion (Tomo2D) with good ray coverage down to the mantle. Slow-spreading Paleocene oceanic crust has a thickness of 5 km, while the Eocene crust created by ultraslow spreading is as thin as 3.5 km. The upper crustal velocity is affected by fracturation due to a dominant tectonic extension during the waning stage of spreading, with a velocity drop of 0.5 to 1 km/s when compared to Paleocene upper crustal velocities (5.2-6.0 km/s). The overall crustal structure is similar to active ultraslow-spreading centers like the Mohns Ridge or the South West Indian Ridge with lower crustal velocities of 6.0-7.0 km/s. An oceanic core complex is imaged on a 50 km long segment of the ridge perpendicular line with serpentinized peridotites (7.3-7.9 km/s) found 1.5 km below the basement. The second, ridge-parallel line also shows extremely thin crust in the extinct axial valley, where 8 km/s mantle velocity is imaged just 1.5 km below the basement. This thin crust is interpreted as crust formed by ultraslow spreading, which was thinned by tectonic extension.