Seismic evidence for a deep upper mantle thermal anomaly beneath east Africa

Nyblade, A.; Owens, Thomas; Gurrola, H.; Ritsema, Jeroen; Langston, Charles A.

doi:10.1130/0091-7613(2000)28<599:sefadu>2.0.co;2

Cited by 136 publications

(107 citation statements)

References 38 publications

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“…It is tempting to speculate that the Red Sea opening may be one of the consequences of the presence of a mega plume that extends from the core-mantle boundary into the upper mantle beneath east Africa, the Red Sea, and the western portion of the Arabian plate [45,46]. It is possible that this mega plume may have rivaled those that drove the break up of Gondwanaland and Pangea.…”

Section: Discussionmentioning

confidence: 99%

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

Aldamegh¹,

Sandvol²,

Barazangi³

2005

Earth and Planetary Science Letters

133

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We also employed a grid search waveform modeling technique to estimate the crustal velocity structure for seven stations. A jackknife re-sampling approach was used to estimate errors in the grid search results for three stations. In addition to our results, we have also included published receiver function results from two temporary networks in the Arabian shield and Oman as well as three permanent GSN stations in the region.The average crustal thickness of the late Proterozoic Arabian shield is 39 km. The crust thins to about 23 km along the Red Sea coast and to about 25 km along the margin of the Gulf of Aqaba. In the northern part of the Arabian platform, the crust varies from 33 -37 km thick.However, the crust is thicker (41 -53 km) in the southeastern part of the platform. There is a dramatic change in crustal thickness between the topographic escarpment of the Arabian shield and the shorelines of the Red Sea. We compared our results in the Arabian shield to nine other Proterozoic and Archean shields that include reasonably well-determined Moho depths, mostly based on receiver functions. The average crustal thickness for all shields is 39 km, while the average for Proterozoic shields is 40 km, and the average for Archean shields is 38 km. We found the crustal thickness of Proterozoic shields to vary between 33 and 44 km, while Archean shields vary between 32 and 47 km. Overall, we do not observe a significant difference between Proterozoic and Archean crustal thickness. 3We observed a dramatic change in crustal thickness along the Red Sea margin that occurs over a very short distance. We projected our results over a cross section extending from the Red Sea ridge to the shield escarpment and contrasted it with a typical Atlantic margin. The transition from oceanic to continental crust of the Red Sea margin occurs over a distance of about 250 km, while the transition along a typical portion of the western Atlantic margin occurs at a distance of about 450 km. This important new observation highlights the abruptness of the breakup of Arabia. We argue that a preexisting zone of weakness coupled with anomalously hot upper mantle could have initiated and expedited the breakup.

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Section: Discussionmentioning

confidence: 99%

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

Aldamegh¹,

Sandvol²,

Barazangi³

2005

Earth and Planetary Science Letters

133

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“…Ritsema et al [1998] also imaged a region of fast wave speeds beneath the Tanzania Craton, showing that the lithospheric keel of the craton extends to a depth of $150-200 km. The westward dipping LWA was attributed to the flow of a mantle plume around the lithospheric keel of the Tanzania Craton by Nyblade et al [2000].…”

Section: Previous Seismic Studiesmentioning

confidence: 99%

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Mulibo

Nyblade

2013

Geochem Geophys Geosyst

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P and S relative arrival time residuals from teleseismic earthquakes recorded on over 60 temporary AfricaArray broadband seismic stations deployed in Uganda, Tanzania, and Zambia between 2007 and 2011 have been inverted, together with relative arrival time residuals from earthquakes recorded by previous deployments, for a tomographic image of mantle wave speed variations extending to a depth of 1200 km beneath eastern Africa. The image shows a low‐wave speed anomaly (LWA) well developed at shallow depths (100–200 km) beneath the Eastern and Western branches of the Cenozoic East African rift system and northwestern Zambia, and a fast wave speed anomaly at depths ≤ 350 km beneath the central and northern parts of the East African Plateau and the eastern and central parts of Zambia. At depths ≥350 km the LWA is most prominent under the central and southern parts of the East African Plateau and dips to the southwest beneath northern Zambia, extending to a depth of at least 900 km. The amplitude of the LWA is consistent with a ∼150–300 K thermal perturbation, and its depth extent indicates that the African superplume, originally identified as a lower mantle anomaly, is likely a whole mantle structure. A superplume extending from the core‐mantle boundary to the surface implies an origin for the Cenozoic extension, volcanism, and plateau uplift in eastern Africa rooted in the dynamics of the lower mantle.

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“…Regions of pre-existing weakness and/or thin lithosphere are proposed to control lateral transport of hot plume material and where it ponds and escapes to the surface as a volcanic centre, as seen along the Western Branch (e.g. Nyblade et al 2000). Studies of shear wave splitting further promote the idea of broad scale alongaxis mantle flow beneath the EARS (Bagley & Nyblade 2013;Tepp 2016), although pre-existing lithospheric fabrics may also play a role (Walker et al 2004).…”

Section: The Rungwe Volcanic Province: the Localization Of Magmatism mentioning

confidence: 99%

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

Accardo

Gaherty

Shillington

et al. 2017

Geophysical Journal International

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Seismic evidence for a deep upper mantle thermal anomaly beneath east Africa

Cited by 136 publications

References 38 publications

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

Crustal structure of the Arabian plate: new constraints from the analysis of teleseismic receiver functions

The P and S wave velocity structure of the mantle beneath eastern Africa and the African superplume anomaly

Surface wave imaging of the weakly extended Malawi Rift from ambient-noise and teleseismic Rayleigh waves from onshore and lake-bottom seismometers

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