Crustal structure of the ultra-slow spreading Knipovich Ridge,North Atlantic,along a presumed ridge segment center |
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| Authors: | Aleksandre Kandilarov Hildegunn Landa Rolf Mjelde Rolf B Pedersen Kyoko Okino Yoshio Murai |
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| Institution: | (1) Department of Earth Science, University of Bergen, Allegaten 41A, 5007 Bergen, Norway;(2) Ocean Research Institute, University of Tokyo, Tokyo, Japan;(3) Institute of Seismology and Volcanology, Hokkaido University, Sapporo, Japan |
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| Abstract: | A combined ocean bottom seismometer, multichannel seismic reflection and gravity study has been carried out along the spreading
direction of the Knipovich Ridge over a topographic high that defines a segment center. The youngest parts of the crust in
the immediate vicinity of the ridge reveal fractured Oceanic Layer 2 and thermally expanded and possibly serpentinized Oceanic
Layer 3. The mature part of the crust has normal thickness and seismic velocities with no significant crustal thickness and
seismic velocity variations. Mature Oceanic Layer 2 is in addition broken into several rotated fault blocks. Comparison with
a profile acquired ~40 km north of the segment center reveals significant differences. Along this profile, reported earlier,
periods of slower spreading led to generation of thin crust with a high P-wave velocity (Vp), composed of a mixture of gabbro and serpentinized mantle, while periods of faster spreading led to generation of more
normal gabbroic crust. For the profile across the segment center no clear relation exists between spreading rate and crustal
thickness and seismic velocity. In this study we have found that higher magmatism may lead to generation of oceanic crust
with normal thickness even at ultra-slow spreading rates. |
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