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

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

doi:10.1029/2019jb019100

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

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

Authors

R.G. Davy

J.S. Collier

T.J. Henstock

Andreas Rietbrock

Saskia Goes

Jon Blundy

Nick Harmon

Catherine Rychert

Professor Colin Macpherson colin.macpherson@durham.ac.uk
Professor

Professor Jeroen Van Hunen jeroen.van-hunen@durham.ac.uk
Professor

Mike Kendall

Jamie Wilkinson

Jon Davidson

Marjorie Wilson

George Cooper

Benjamin Maunder

Lidong Bie

Stephen Hicks

Robert Allen

Ben Chichester

Stephen Tait

Richie Robertson

Joan Latchman

Frank Krüger

Jenny Collier

Tim Henstock

Sophie Butcher

Gabriella Castiello

Chen Chen

Caroline Harkin

Dan Posse

Ben Roche

Anna Bird

Andy Clegg

Ben Pitcairn

Martin Weeks

Henning Kirk

Erik Labahn

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.

Citation

Davy, R., Collier, J., Henstock, T., Rietbrock, A., Goes, S., Blundy, J., …Labahn, E. (2020). Wide‐Angle Seismic Imaging of Two Modes of Crustal Accretion in Mature Atlantic Ocean Crust. Journal of Geophysical Research. Solid Earth, 125(6), Article e2019JB019100. https://doi.org/10.1029/2019jb019100

Journal Article Type	Article
Acceptance Date	Apr 16, 2020
Online Publication Date	Jun 20, 2020
Publication Date	2020-06
Deposit Date	Jun 24, 2020
Publicly Available Date	Jun 24, 2020
Journal	Journal of Geophysical Research. Solid Earth
Print ISSN	2169-9313
Electronic ISSN	2169-9356
Publisher	American Geophysical Union
Peer Reviewed	Peer Reviewed
Volume	125
Issue	6
Article Number	e2019JB019100
DOI	https://doi.org/10.1029/2019jb019100

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Copyright Statement
© 2020. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.