Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E.

Fromm, Tanja, Jokat, Wilfried and Behrmann, Jan H. (2017) Interaction between a hotspot and a fracture zone: The crustal structure of Walvis Ridge at 6° E. Open Access Tectonophysics, 716 . pp. 108-120. DOI 10.1016/j.tecto.2017.03.001.

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Supplementary data:

Abstract

Highlights

• Late stage volcanism covers old oceanic crust north of the Florianopolis Fracture Zone.
• No influence of fracture zone on formation of Walvis Ridge at 6° E.
• Walvis Ridge at 6° E erupted in deep water environment.

Abstract

The Walvis Ridge is one of the major hotspot trails in the South Atlantic and a classical example for volcanic island chains. Two models compete about the origin of the ridge: It is either the result of a deep mantle plume or active fracture zones above mantle inhomogeneities. Among other things crustal information is needed to constrain the models. Here, we provide such constraint with a 480 km long P-wave velocity model of the deep crustal structure of the eastern Walvis Ridge at 6° E. According to our data the Walvis Ridge stretches across the Florianopolis Fracture Zone into the Angola Basin. Here, we observe a basement high and thick basaltic layers covering the oceanic crust and the fracture zone. We found two crustal roots along the profile: one is located beneath the ridge crest, the other one beneath the northern basement high in the Angola Basin. The crustal thickness reaches 18 km and 12 km and the lower crustal velocities are 7.2 km/s and 7.4 km/s, respectively. The bathymetric expression of the ridge along the profile is less pronounced than closer to shore, which is mainly attributable to the absence of a thick layer of volcanic debris, rather than to reduced crustal thickness below the basement surface. Therefore, this part of the ridge was never or only briefly subaerially exposed. The crustal structure suggests that the ridge and the fracture zone formed independently of each other. The oceanic crust north of the fracture zone, which is buried underneath the basalt layer, is younger than the reconstructed age of hotspot volcanism of the Walvis Ridge. We interpret these structures north of the fracture zone to be at least partly a product of late stage volcanism.

Document Type: Article
Keywords: refraction seismic; crustal structure; hotspot; South Atlantic Opening, Walvis Ridge
Research affiliation: AWI
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.2017.03.001
ISSN: 0040-1951
Projects: Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 13 Mar 2017 10:18
Last Modified: 04 Mar 2019 00:38
URI: http://oceanrep.geomar.de/id/eprint/36905

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