South Atlantic opening: A plume-induced breakup?

Fromm, Tanja; Planert, Lars; Jokat, Wilfried; Ryberg, Trond; Behrmann, Jan H.; Weber, M.; Haberland, Christian

doi:10.1130/g36936.1

Cited by 59 publications

(75 citation statements)

References 32 publications

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“…The main ridge is not characterized by the exceptionally high velocities (> 7.2 km/s) occasionally observed at other hot spot trails (e.g. the Ninetyeast Ridge, Grevemeyer et al, 2001) or under the Walvis Ridge more close to the Namibian margin (Fromm et al, 2015).…”

Section: The Ridge Crestmentioning

confidence: 99%

“…2). Here, the ridge forms a bathymetric saddle 1000 m deeper than at the western end of P100, 200 km Location of the presented profile 150 crossing the Walvis Ridge ∼600 km east of the African coastline and other deep seismic profiles from the same campaign (Fromm et al, 2015) . Note that the bathymetric expression at the intersection of the profile with the ridge less prominent compared to the East and the Florianopolis Fracture zone is not visible in the bathymetry.…”

Section: Seismic Datamentioning

confidence: 99%

“…Becker et al, 2012;Becker et al, 2014;Hirsch et al, 2009;Bauer et al, 2000;Fromm et al, 2015), but despite their importance, seismic data revealing the crustal structure in this region are rare. Here, we present details of a seismic refraction profile (Fromm et al, 2015) acquired 600 km west of the Namibian coast that provides new information on the crustal fabric underlying a topographically subdued part of Walvis Ridge. One hypothesis to be checked was that the part of the ridge with a subdued topography might be underlain by thinner crust, thus indicating several phases of the ridge evolution.…”

Section: Introductionmentioning

confidence: 99%

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

2017

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A B S T R A C TThe 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.

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Section: The Ridge Crestmentioning

confidence: 99%

Section: Seismic Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2017

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“…On the conjugate margin of Namibia/South Africa, high seismic velocities (up to >7 km/s) also point to a gabbroic composition of the lower crust (Fromm et al, 2015).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust

et al. 2018

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, Rifted margins: Ductile deformation, boudinage, continentward-dipping normal faults and the role of the weak lower crust, (2016), doi: 10.1016/j.gr.2017.04.030 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T Abstract:The

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“…Although kimberlites are in general considered to be formed by an interaction of a plume with continental crust, the studies on the OJP suggest that an interaction of the anomalously thick LIP crust with ascending magma of a plume results in similar chemical signatures (Nixon 1980;Ishikawa 2011). A comparison to hotspot volcanism seen within tectonically faulted continental crust, for example at the Walvis Ridge (Fromm et al 2015), shows that hotspot volcanism is restricted to a distinct, small area that is located above the assumed hotspot path. We conclude that LIP crust, although different in composition and thickness, acts more like continental crust when interacting with hotspot magmatism.…”

Section: Implications and Comparison To Other Lipsmentioning

confidence: 99%