Publication Date:
2017-04-19
Description:
〈span class="paragraphSection"〉〈div class="boxTitle"〉Summary〈/div〉The oceanic crustal and uppermost lithospheric mantle structure across the Gloria Fault (GF) transcurrent plate boundary between Africa and Eurasia in the Northeast Atlantic is investigated based on seismic reflection, seismic refraction and wide-angle reflection data. This experiment used 18 ocean bottom stations along an N–S 150 km long traverse together with acquisition of a multichannel seismic reflection profile. Modeling of 〈span style="font-style:italic;"〉P〈/span〉 and 〈span style="font-style:italic;"〉S〈/span〉 seismic waves and gravimetric anomalies allowed estimation of 〈span style="font-style:italic;"〉P〈/span〉- and 〈span style="font-style:italic;"〉S〈/span〉-wave velocities, density, Poisson's ratio and discussion of a compositional model. A five-layer model is proposed in which layers 1–3 correspond to normal sediments through typical oceanic crust layers 2 and 3. Layer 5 yielded mantle velocities above 7.9 km s〈sup〉−1〈/sup〉. Layer 4 with 4 km of thickness has 〈span style="font-style:italic;"〉Vp〈/span〉 velocities between 7.1 and 7.4 km s〈sup〉−1〈/sup〉 and is clearly separated from typical oceanic crust and mantle layers. Comparison with natural analogues and published lab measurements suggest that layer 4 can be a mix of lithologies that comply with the estimated 〈span style="font-style:italic;"〉P〈/span〉 and 〈span style="font-style:italic;"〉S〈/span〉 velocities and computed Poisson's ratio and densities, such as, olivine cumulates, peridotite, gabbro and hydrated mantle. We favour the tectonic process that produces secondary porosity from which results serpentinization due to sea water circulation in fractures. Structural and seismic stratigraphic interpretation of the reflection profile shows that Neogene to recent tectonic deformation on this segment of the plate boundary concentrated on the southern side of the GF, that is, the Africa plate.〈/span〉
Print ISSN:
0956-540X
Electronic ISSN:
1365-246X
Topics:
Geosciences
Published by
Oxford University Press
on behalf of
The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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