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Journal Articles Journal of Geophysical Research : Solid Earth Year : 2020

Wide-Angle Seismic Imaging of Two Modes of Crustal Accretion in Mature Atlantic Ocean Crust

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R. G. Davy
  • Function : Author
J. S. Collier
  • Function : Author
T. J. Henstock
  • Function : Author
Saskia Goes
  • Function : Author
Jon Blundy
  • Function : Author
Nick Harmon
  • Function : Author
Catherine Rychert
  • Function : Author
Colin G. Macpherson
  • Function : Author
Jeroen van Hunen
  • Function : Author
Mike Kendall
  • Function : Author
Jamie Wilkinson
  • Function : Author
Jon Davidson
  • Function : Author
Marjorie Wilson
  • Function : Author
George Cooper
  • Function : Author
Benjamin Maunder
  • Function : Author
Lidong Bie
  • Function : Author
Stephen Hicks
  • Function : Author
Ben Chichester
  • Function : Author
Stephen Tait
  • Function : Author
Richie Robertson
  • Function : Author
Jenny Collier
  • Function : Author
Tim Henstock
  • Function : Author
Robert Allen
  • Function : Author
Sophie Butcher
  • Function : Author
Gabriella Castiello
  • Function : Author
Chen Chen
  • Function : Author
Caroline Harkin
  • Function : Author
Dan Posse
  • Function : Author
Ben Roche
  • Function : Author
Anna Bird
  • Function : Author
Andy Clegg
  • Function : Author
Ben Pitcairn
  • Function : Author
Martin Weeks
  • Function : Author
Henning Kirk
  • Function : Author
Erik Labahn
  • Function : Author

Abstract

We present a high-resolution 2-D P-wave velocity model from a 225-km-long active seismic profile, collected over ~60-75 Ma central Atlantic crust. The profile crosses five ridge segments separated by a transform and three nontransform offsets. All ridge discontinuities share similar primary characteristics, independent of the offset. We identify two types of crustal segment. The first displays a classic two-layer velocity structure with a high gradient Layer 2 (~0.9 s-1) above a lower gradient Layer 3 (0.2 s-1). Here, PmP coincides with the 7.5 km s-1 contour, and velocity increases to >7.8 km s-1 within 1 km below. We interpret these segments as magmatically robust, with PmP representing a petrological boundary between crust and mantle. The second has a reduced contrast in velocity gradient between the upper and lower crust and PmP shallower than the 7.5 km s-1 contour. We interpret these segments as tectonically dominated, with PmP representing a serpentinized (alteration) front. While velocity-depth profiles fit within previous envelopes for slow-spreading crust, our results suggest that such generalizations give a misleading impression of uniformity. We estimate that the two crustal styles are present in equal proportions on the floor of the Atlantic. Within two tectonically dominated segments, we make the first wide-angle seismic identifications of buried oceanic core complexes in mature (>20 Ma) Atlantic Ocean crust. They have a ~20-km-wide "domal" morphology with shallow basement and increased upper crustal velocities. We interpret their midcrustal seismic velocity inversions as alteration and rock-type assemblage contrasts across crustal-scale detachment faults.
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insu-03584765 , version 1 (24-02-2022)

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R. G. Davy, J. S. Collier, T. J. Henstock, Saskia Goes, Jon Blundy, et al.. Wide-Angle Seismic Imaging of Two Modes of Crustal Accretion in Mature Atlantic Ocean Crust. Journal of Geophysical Research : Solid Earth, 2020, 125, pp.3011-3053. ⟨10.1029/2019JB019100⟩. ⟨insu-03584765⟩
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