Non‐uniform splitting of a single mantle plume by double cratonic roots: Insight into the origin of the central and southern East African Rift System

Koptev, Alexander; Cloetingh, S.A.P.L.; Gerya, Taras; Calais, E.; Leroy, Sylvie

doi:10.1111/ter.12317

Cited by 24 publications

(33 citation statements)

References 90 publications

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“…A slightly more complex model setup, with a craton embedded in the EARS lithosphere (model 10), is shown on Figure . Similarly to previous 3‐D experiments (Burov & Gerya, ; Koptev et al, , , ), this model predicts a rapid mantle ascent (vertical speed of ~80 cm/yr) with the plume head reaching the base of the lithosphere 0.5 Myr into the model evolution. The plume material is then deflected to the eastern side of the craton, where it generates a broad topographic high reaching a maximum of 2 km similar in spatial extent to the Kenya dome of the central EARS (Figure ).…”

Section: Resultssupporting

confidence: 79%

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

Koptev

Calais

Burov

et al. 2018

Geophysical Research Letters

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Narrow and wide rifts are end‐member expressions of continental extension. Within the framework of passive rifting, the transition from wide to narrow rifts requires lowering the geothermal gradient. Reconciling this view with observational evidence for narrow rift zones in regions underlain by sublithospheric hot plume material, such as the eastern branch of the East African Rift, requires invoking preexisting weak zones for strain to localize in a warm crust. Based on thermomechanical numerical models, we show that along‐rift width variations can develop spontaneously as a consequence of spatial variations of the geotherm over an evolving mantle plume impinging a lithosphere subjected to ultraslow extension. The eastern branch of the East African Rift, with a narrow Kenya segment underlain by a mantle plume head and widening to the north and south in the colder regions of the Turkana depression and North Tanzania divergence, is in agreement with this numerical prediction.

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Section: Resultssupporting

confidence: 79%

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

Koptev

Calais

Burov

et al. 2018

Geophysical Research Letters

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“…Recent results of spherical shell finite element modelling of regional stress and strain field in Africa has shown that compressional stresses applied at the mid-ocean ridges surrounding Africa result in rift-perpendicular deviatoric extension in the East African rift valleys that, being combined with upwelling mantle plume(s), leads to localization of extensional deformation and explains the initial lithosphere break-up in the East Africa and the Afar 32 . Likewise, recent 3D thermo-mechanical deformation models show that pre-stressed lithosphere subjected to EW extension is a necessary initial condition for plume-induced localized rifts to develop in the central part of the East African Rift 8 , 9 , 33 .…”

Section: A Type-locale For Triple Junctions: the Afar Regionmentioning

confidence: 98%

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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“…The EARS represents an ideal laboratory for studying magma-poor rifting because it comprises the two contrasting magmatic styles of rifting with the eastern branch being magma rich and the western branch being magma poor [ Figure 1; Koptev et al, 2015Koptev et al, , 2018 and references therein]. The western branch includes rift segments, such as the Malawi Rift, that are considered well developed in terms of morphological expression yet have only isolated zones of magmatism.…”

Section: Introductionmentioning

confidence: 99%

Lithospheric Structure of the Malawi Rift: Implications for Magma‐Poor Rifting Processes

et al. 2019

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Our understanding of how magma‐poor rifts accommodate strain remains limited largely due to sparse geophysical observations from these rift systems. To better understand the magma‐poor rifting processes, we investigate the lithospheric structure of the Malawi Rift, a segment of the magma‐poor western branch of the East African Rift System. We analyze Bouguer gravity anomalies from the World Gravity Model 2012 using the two‐dimensional (2‐D) radially averaged power‐density spectrum technique and 2‐D forward modeling to estimate the crustal and lithospheric thickness beneath the rift. We find: (1) relatively thin crust (38–40 km) beneath the northern Malawi Rift segment and relatively thick crust (41–45 km) beneath the central and southern segments; (2) thinner lithosphere beneath the surface expression of the entire rift with the thinnest lithosphere (115–125 km) occurring beneath its northern segment; and (3) an approximately E‐W trending belt of thicker lithosphere (180–210 km) beneath the rift's central segment. We then use the lithospheric structure to constrain three‐dimensional numerical models of lithosphere‐asthenosphere interactions, which indicate ~3‐cm/year asthenospheric upwelling beneath the thinner lithosphere. We interpret that magma‐poor rifting is characterized by coupling of crust‐lithospheric mantle extension beneath the rift's isolated magmatic zones and decoupling in the rift's magma‐poor segments. We propose that coupled extension beneath rift's isolated magmatic zones is assisted by lithospheric weakening due to melts from asthenospheric upwelling whereas decoupled extension beneath rift's magma‐poor segments is assisted by concentration of fluids possibly fed from deeper asthenospheric melt that is yet to breach the surface.

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Non‐uniform splitting of a single mantle plume by double cratonic roots: Insight into the origin of the central and southern East African Rift System

Abstract: To cite this version:Alexander Koptev, Sierd Cloetingh, Taras Gerya, Eric Calais, Sylvie Leroy. Non-uniform splitting of a single mantle plume by double cratonic roots: Insight into the origin of the central and southern East African Rift System. Terra Nova, Wiley-Blackwell, 2017, 30 (2)

Cited by 24 publications

References 90 publications

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

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

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

Lithospheric Structure of the Malawi Rift: Implications for Magma‐Poor Rifting Processes

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