Along‐Axis Variations of Rift Width in a Coupled Lithosphere‐Mantle System, Application to East Africa

Koptev, Alexander; Calais, E.; Burov, Evgenii; Leroy, Sylvie; Gerya, Taras

doi:10.1029/2018gl077276

Cited by 22 publications

(17 citation statements)

References 76 publications

(114 reference statements)

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“…Plume-craton interaction has been extensively investigated 12,13,62,63 with 3D upper mantle box models. Counterclockwise rotation of a central cratonic block was obtained in several model configurations 13 , including models with a single-plume offset from the center and with two plumes impinging on the NE and SW corners of the craton.…”

Section: Discussionmentioning

confidence: 99%

“…Based on the above, we simplify our extensional boundary conditions to orthogonal, constant velocities 32,63 , applied such that the material is moving outward with a velocity of v x ¼ 1 2 Á 5 mm yr À1 on the right and left boundary (the tangential velocity components are left free). This outflow is compensated by inflow of an equal volume of material through the bottom boundary, and the front and back boundaries feature free slip.…”

Section: Methodsmentioning

confidence: 99%

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Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift

et al. 2020

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The Victoria microplate between the Eastern and Western Branches of the East African Rift System is one of the largest continental microplates on Earth. In striking contrast to its neighboring plates, Victoria rotates counterclockwise with respect to Nubia. The underlying cause of this distinctive rotation has remained elusive so far. Using 3D numerical models, we investigate the role of pre-existing lithospheric heterogeneities in continental microplate rotation. We find that Victoria's rotation is primarily controlled by the distribution of rheologically stronger zones that transmit the drag of the major plates to the microplate and of the mechanically weaker mobile belts surrounding Victoria that facilitate rotation. Our models reproduce Victoria's GPS-derived counterclockwise rotation as well as key complexities of the regional tectonic stress field. These results reconcile competing ideas on the opening of the rift system by highlighting differences in orientation of the far-field divergence, local extension, and the minimum horizontal stress.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift

et al. 2020

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“…The latter propagates southward forming an extension-perpendicular, NS-trending rift similar to the eastern branch of the Central East African rift system (i.e., Kenyan rift). However, it is not straightforward to extrapolate the model results to south of the Main Ethiopian rift where the system is complicated by the stress transmission across the strong Tanzanian craton to the western branch 45 and by the presence of low velocity anomaly in the upper mantle beneath Kenya and northern Tanzania 46 – 48 that controls along-axis rift variations in the eastern branch 49 . Also, an additional rift arm west of the Red Sea that trends WSW-ENE does not find its reflection in nature.…”

Section: Implications For the Afar Triple Junctionmentioning

confidence: 99%

Afar triple junction triggered by plume-assisted bi-directional continental break-up

Koptev

Gerya

Calais

et al. 2018

Sci Rep

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Divergent ridge-ridge-ridge (R-R-R) triple junctions are one of the most remarkable, yet largely enigmatic, features of plate tectonics. The juncture of the Arabian, Nubian, and Somalian plates is a type-example of the early development stage of a triple junction where three active rifts meet at a ‘triple point’ in Central Afar. This structure may result from the impingement of the Afar plume into a non-uniformly stressed continental lithosphere, but this process has never been reproduced by self-consistent plume-lithosphere interaction experiments. Here we use 3D thermo-mechanical numerical models to examine the initiation of plume-induced rift systems under variable far-field stress conditions. Whereas simple linear rift structures are preferred under uni-directional extension, we find that more complex patterns form in response to bi-directional extension, combining one or several R-R-R triple junctions. These triple junctions optimize the geometry of continental break-up by minimizing the amount of dissipative mechanical work required to accommodate multi-directional extension. Our models suggest that Afar-like triple junctions are an end-member mode of plume-induced bi-directional rifting that combines asymmetrical northward pull and symmetrical EW extension at similar rates.

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“…They explained that the Kenya rift developed as a narrow rift segment within the Eastern Branch because of an uprising mantle plume head (Kenya plume head) beneath the rift that heated the lithosphere, and hence thermally weakened it. On the other hand, Koptev et al () explained the development of the Turkana rifted zone within the TD in the north and the North Tanzania Divergence to the south (Figure a) as wide rift segments as due to the presence of colder lithosphere beneath these rift segments of the Eastern Branch.…”

Section: Discussionmentioning

confidence: 99%

Development of Late Jurassic‐Early Paleogene and Neogene‐Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

Emishaw

Abdelsalam

2019

Tectonics

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The Turkana Depression (TD) is a NW trending topographic corridor within the East African Rift System between the Ethiopia‐Yemen plateau in the northeast and the East African plateau to the southwest. The Anza rift within the TD is a NW‐SE trending failed arm of a late Jurassic rift‐rift‐rift triple junction. This rift is correlated with the Sudan and South Sudan rifts. The Anza rift is intersected by the East African Rift System represented by the N‐S trending Turkana rifted zone. We image the lithospheric structure beneath the TD using satellite gravity data. We also use these data to model crustal density distribution beneath the Kino Sogo fault belt, part of the Turkana rifted zone. Our results show thinner crust (23–28 km) and lithosphere (140–150 km) beneath the TD. We interpret this as due to extension that resulted in the formation of the Kenya‐Sudan and South Sudan rifts. Our results also show that crustal depth between 0 and 4.8 km is dominated by N‐S density contrast anomalies and between 4.8 and 14.5 km by E‐W anomalies. We interpret the N‐S anomalies as due to the presence of Precambrian structure that might have facilitated strain localization during the initiation of the Kino Sogo fault belt. Differently, we interpret the E‐W anomalies as due to the presence E‐W trending faults that were formed in association with the development of the Anza rift and/or Turkana rifted zone and were later filled with Mesozoic and Cenozoic mafic dikes.

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Along‐Axis Variations of Rift Width in a Coupled Lithosphere‐Mantle System, Application to East Africa

Cited by 22 publications

References 76 publications

Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift

Victoria continental microplate dynamics controlled by the lithospheric strength distribution of the East African Rift

Afar triple junction triggered by plume-assisted bi-directional continental break-up

Development of Late Jurassic‐Early Paleogene and Neogene‐Quaternary Rifts Within the Turkana Depression, East Africa From Satellite Gravity Data

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