3-D Magnetotelluric Image of Offshore Magmatism at the Walvis Ridge and Rift Basin.

Jegen, Marion, Avdeeva, Anna, Berndt, Christian, Franz, Gesa, Heincke, Björn, Hölz, Sebastian, Neska, Anne, Marti, Anna, Planert, Lars, Chen, Jin, Kopp, Heidrun, Baba, Kiyoshi, Ritter, Oliver, Weckmann, Ute, Meqbel, Naser and Behrmann, Jan (2016) 3-D Magnetotelluric Image of Offshore Magmatism at the Walvis Ridge and Rift Basin. Open Access Tectonophysics, 683 . pp. 98-108. DOI 10.1016/j.tecto.2016.06.016.

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Supplementary data:

Abstract

Highlights

• We report on marine 3D Magnetotelluric study on Walvis Ridge
• Derived 3D electrical resistivity model shows a large scale resistive zone, which we link to crustal extension due to local uplift. It might indicate the location where the hot-spot impinged on the crust prior to rifting
• Smaller scale resistive region is attributed to magma ascent during rifting
• Rift basin is identified by low resistivity region

The Namibian continental margin marks the starting point of the Tristan da Cunha
hotspot trail, the Walvis Ridge. This section of the volcanic southwestern African
margin is therefore ideal to study the interaction of hotspot volcanism and rifting,
which occurred in the late Jurassic/early Cretaceous. Offshore magnetotelluric data
image electromagnetically the landfall of Walvis Ridge. Two large-scale high
resistivity anomalies in the 3-D resistivity model indicate old magmatic intrusions
related to hot-spot volcanism and rifting. The large-scale resistivity anomalies
correlate with seismically identified lower crustal high velocity anomalies attributed
to magmatic underplating along 2-D offshore seismic profiles. One of the high
resistivity anomalies (above 500 Ωm) has three arms of approximately 100 km width
and 300 km to 400 km length at 120 degree angles in the lower crust. One of the arms
stretches underneath Walvis Ridge. The shape is suggestive of crustal extension due
to local uplift. It might indicate the location where the hot-spot impinged on the crust
prior to rifting. A second, smaller anomaly of 50 km width underneath the continent
ocean boundary may be attributed to magma ascent during rifting. We attribute a low
resistivity anomaly east of the continent ocean boundary and south of Walvis Ridge to
the presence of a rift basin that formed prior to the rifting.

Document Type: Article
Keywords: Offshore magmatism, Walvis Ridge, RV Maria S. Merian, MSM17/1, MSM17/2, Ocean Bottom Electromagnetic (OBEM) instruments
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R03
OceanRep > The Future Ocean - Cluster of Excellence > FO-R06
OceanRep > The Future Ocean - Cluster of Excellence
GFZ
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.tecto.2016.06.016
ISSN: 0040-1951
Projects: Future Ocean, SAMPLE (SPP 1375)
Expeditions/Models/Experiments:
Date Deposited: 23 Jun 2016 07:07
Last Modified: 01 Jul 2018 23:38
URI: http://oceanrep.geomar.de/id/eprint/33154

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