TY - JOUR
T1 - Wide-angle seismic imaging of two modes of crustal accretion in mature Atlantic Ocean crust
AU - Davy, R. G.
AU - Collier, J. S.
AU - Henstock, Tim
AU - Rietbrock, Andreas
AU - Goes, Saskia
AU - Blundy, Jon
AU - Harmon, Nick
AU - Rychert, Catherine
AU - Macpherson, Colin G.
AU - Van Hunen, Jeroen
AU - Kendall, Mike
AU - Wilkinson, Jamie
AU - Davidson, Jon
AU - Wilson, Marjorie
AU - Cooper, George
AU - Maunder, Benjamin
AU - Bie, Lidong
AU - Hicks, Stephen
AU - Allen, Robert
AU - Chichester, Ben
AU - Tait, Stephen
AU - Robertson, Richie
AU - Latchman, Joan
AU - Krüger, Frank
AU - Collier, Jenny
AU - Henstock, Tim
AU - Allen, Robert
AU - Butcher, Sophie
AU - Castiello, Gabriella
AU - Chen, Chen
AU - Harkin, Caroline
AU - Posse, Dan
AU - Roche, Ben
AU - Bird, Anna
AU - Clegg, Andy
AU - Pitcairn, Ben
AU - Weeks, Martin
AU - Kirk, Henning
AU - Labahn, Erik
N1 - Funding Information:
This work was funded under Natural Environment Research Council (NERC) Grants NE/K010743/1 and NE/K010654/1 (VoiLA). We thank the captain, John Leask, officers, crew, and science party members who sailed on RRS cruise JC149‐leg3 (science party members are listed in Appendix A2 ) (Collier, 2017 ). We thank the UK Ocean‐Bottom Instrumentation Facility (Minshull et al., 2005 ) and the German Instrument Pool for Amphibian Seismology (DEPAS), hosted by the Alfred Wegener Institute Bremerhaven, for providing the ocean‐bottom seismometers. We thank the members of the VoiLA consortium for their contributions to this paper (for a full list of VoiLA consortium members, see Appendix A1 ). This article was greatly improved by feedback from Matthias Delescluse and two anonymous reviewers. Swath bathymetry and wide‐angle seismic data from cruise JC149 are available from the Marine Geoscience Data System ( http://www.marine‐geo.org/tools/search/entry.php?id=JC149 , DOI: 10.26022/IEDA/327347 ). James Cook
Funding Information:
This work was funded under Natural Environment Research Council (NERC) Grants NE/K010743/1 and NE/K010654/1 (VoiLA). We thank the captain, John Leask, officers, crew, and science party members who sailed on RRS James Cook cruise JC149-leg3?(science party members are listed in Appendix A2) (Collier,?2017). We thank the UK Ocean-Bottom Instrumentation Facility (Minshull et al.,?2005) and the German Instrument Pool for Amphibian Seismology (DEPAS), hosted by the Alfred Wegener Institute Bremerhaven, for providing the ocean-bottom seismometers. We thank the members of the VoiLA consortium for their contributions to this paper (for a full list of VoiLA consortium members, see Appendix A1). This article was greatly improved by feedback from Matthias Delescluse and two anonymous reviewers. Swath bathymetry and wide-angle seismic data from cruise JC149 are available from the Marine Geoscience Data System (http://www.marine-geo.org/tools/search/entry.php?id=JC149, DOI: 10.26022/IEDA/327347).
Publisher Copyright:
©2020. The Authors.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - 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.
AB - 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.
KW - active-source seismic
KW - fracture zone
KW - nontransform offset
KW - oceanic core complexes
KW - slow-spread oceanic crust
KW - tomography
UR - http://www.scopus.com/inward/record.url?scp=85086829944&partnerID=8YFLogxK
U2 - 10.1029/2019JB019100
DO - 10.1029/2019JB019100
M3 - Article
AN - SCOPUS:85086829944
VL - 125
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
SN - 2169-9313
IS - 6
M1 - e2019JB019100
ER -