Plume dynamics beneath the African plate inferred from the geochemistry of the Tertiary basalts of southern Ethiopia

George, Rhiannon; Rogers, Nick

doi:10.1007/s00410-002-0396-z

Cited by 106 publications

(112 citation statements)

References 55 publications

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“…dolerites were intruded during the period 20-12 Ma across the greater part of the margin. The timing coincides with the $19-11 Ma syn-extensional Getra Kele basalts from southern Ethiopia (George and Rogers, 2002). In contrast, Group 4b dikes yield ages clustered around 24 Ma and are restricted to the Desse-Combolcha sector.…”

Section: Group 4 Dikes ($25-12 Ma)supporting

confidence: 61%

“…(b) MgO-X diagrams illustrating the variance between the rift margin and shield building phase of the Ethiopian plateau and Group 4 of this study. We show that Group 4a (19-12 Ma) is distinct from the contemporaneous Getra Kele formation of southern Ethiopia in most element plots (Stewart and Rogers, 1996;George and Rogers, 2002). The distinct major element trends (e.g.…”

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 68%

“…The distinct major element trends (e.g. CaO/Al 2 O 3 ) reflect the unusually deep clinopyroxene-dominated fractionation of the Getra Kele basalts (George and Rogers, 2002). Group 4b displays a similar range in trace elements when compared to the 22-25 Ma Choke and Guguftu shield volcanoes (Kieffer et al, 2004).…”

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 93%

“…5) displayed by the contemporaneous Getra Kele basalts in southern Ethiopia (Stewart and Rogers, 1996;George and Rogers, 2002). Indeed, substantial heterogeneity is evident between the two, where the radiogenic end-member of the Getra Kele Formation appears HIMU-like (George and Rogers, 2002), distinct from the "C" signature of the Afar plume present in all dike groups from the western Afar margin. 5.…”

Section: Group 4 Dikesmentioning

confidence: 99%

“…Our Group 3 differs markedly from the Quaternary rift-floor volcanic in the MER by having much more enriched values of HREE and an overall flatter trace element profile. (d) Group 4a samples are plotted against contemporaneous Getra Kele rift margin basalts of southern Ethiopia (George and Rogers, 2002). While Group 4a plots with the Getra Kele basalts in terms of the more incompatible elements, there is a distinct heterogeneity between the two in terms of the more compatible elements -Group 4a samples are significantly more enriched.…”

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 99%

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Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

Rooney

Mohr

Dosso

et al. 2013

Geochimica et Cosmochimica Acta

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evidence of mantle reservoir evolution during progressive rifting along the western Afar margin. Geochimica et Cosmochimica Acta, Elsevier, 2013Elsevier, , 102, pp.65-88. 10.1016Elsevier, /j.gca.2012 Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin AbstractThe Afar triple junction, where the Red Sea, Gulf of Aden and African Rift System extension zones converge, is a pivotal domain for the study of continental-to-oceanic rift evolution. The western margin of Afar forms the southernmost sector of the western margin of the Red Sea rift where that margin enters the Ethiopian flood basalt province. Tectonism and volcanism at the triple junction had commenced by $31 Ma with crustal fissuring, diking and voluminous eruption of the EthiopianYemen flood basalt pile. The dikes which fed the Oligocene-Quaternary lava sequence covering the western Afar rift margin provide an opportunity to probe the geochemical reservoirs associated with the evolution of a still active continental margin. 40 Ar/ 39 Ar geochronology reveals that the western Afar margin dikes span the entire history of rift evolution from the initial Oligocene flood basalt event to the development of focused zones of intrusion in rift marginal basins. Major element, trace element and isotopic (Sr-Nd-Pb-Hf) data demonstrate temporal geochemical heterogeneities resulting from variable contributions from the Afar plume, depleted asthenospheric mantle, and African lithosphere. The various dikes erupted between 31 Ma and 22 Ma all share isotopic signatures attesting to a contribution from the Afar plume, indicating this initial period in the evolution of the Afar margin was one of magma-assisted weakening of the lithosphere. From 22 Ma to 12 Ma, however, diffuse diking during continued evolution of the rift margin facilitated ascent of magmas in which depleted mantle and lithospheric sources predominated, though contributions from the Afar plume persisted. After 10 Ma, magmatic intrusion migrated eastwards towards the Afar rift floor, with an increasing fraction of the magmas derived from depleted mantle with less of a lithospheric signature. The dikes of the western Afar margin reveal that magma generation processes during the evolution of this continental rift margin are increasingly dominated by shallow decompressional melting of the ambient asthenosphere, the composition of which may in part be controlled by preferential channeling of plume material along the developing neo-oceanic axes of extension.

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Section: Group 4 Dikes ($25-12 Ma)supporting

confidence: 61%

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 68%

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 93%

Section: Group 4 Dikesmentioning

confidence: 99%

Section: Group 4 Dikes ($25-12 Ma)mentioning

confidence: 99%

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Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

Rooney

Mohr

Dosso

et al. 2013

Geochimica et Cosmochimica Acta

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The African landscape through space and time

2014

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Key Points:• We invert large sets of longitudinal river profiles. Fits to data are excellent • Our history of uplift is consistent with independent geological calibration • We have reconstructed the evolution of dynamic topography in Africa since 50 Ma Abstract It is generally accepted that Cenozoic epeirogeny of the African continent is moderated by convective circulation of the mantle. Nevertheless, the spatial and temporal evolution of Africa's "basin-and-swell" physiography is not well known. Here we show how continental drainage networks can be used to place broad constraints on the pattern of uplift through space and time. First, we assemble an inventory of 710 longitudinal river profiles that includes major tributaries of the 10 largest catchments. River profiles have been jointly inverted to determine the pattern of uplift rate as a function of space and time.Our inverse model assumes that shapes of river profiles are controlled by uplift rate history and modulated by erosional processes, which can be calibrated using independent geologic evidence (e.g., marine terraces, volcanism and thermochronologic data). Our results suggest that modern African topography started to develop ∼30 Myr ago when volcanic swells appeared in North and East Africa. During the last 15-20 Myr, subequatorial Africa was rapidly elevated, culminating in the appearance of three large swells that straddle southern and western coasts. Our results enable patterns of sedimentary flux at major deltas to be predicted and tested. We suggest that the evolution of drainage networks is dominated by rapid upstream advection of signals produced by a changing pattern of regional uplift. An important corollary is that, with careful independent calibration, these networks might act as useful tape recorders of otherwise inaccessible mantle processes. Finally, we note that there are substantial discrepancies between our results and published dynamic topographic predictions.

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The Role of Crustal Strength in Controlling Magmatism and Melt Chemistry During Rifting and Breakup

Armitage

Petersen

Pérez‐Gussinyé

2018

Geochem Geophys Geosyst

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The strength of the crust has a strong impact on the evolution of continental extension and breakup. Strong crust may promote focused narrow rifting, while wide rifting might be due to a weaker crustal architecture. The strength of the crust also influences deeper processes within the asthenosphere. To quantitatively test the implications of crustal strength on the evolution of continental rift zones, we developed a 2‐D numerical model of lithosphere extension that can predict the rare Earth element (REE) chemistry of erupted lava. We find that a difference in crustal strength leads to a different rate of depletion in light elements relative to heavy elements. By comparing the model predictions to rock samples from the Basin and Range, USA, we can demonstrate that slow extension of a weak continental crust can explain the observed depletion in melt chemistry. The same comparison for the Main Ethiopian Rift suggests that magmatism within this narrow rift zone can be explained by the localization of strain caused by a strong lower crust. We demonstrate that the slow extension of a strong lower crust above a mantle of potential temperature of 1,350 °C can fit the observed REE trends and the upper mantle seismic velocity for the Main Ethiopian Rift. The thermo‐mechanical model implies that melt composition could provide quantitative information on the style of breakup and the initial strength of the continental crust.

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Plume dynamics beneath the African plate inferred from the geochemistry of the Tertiary basalts of southern Ethiopia

Cited by 106 publications

References 55 publications

Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

Geochemical evidence of mantle reservoir evolution during progressive rifting along the western Afar margin

The African landscape through space and time

The Role of Crustal Strength in Controlling Magmatism and Melt Chemistry During Rifting and Breakup

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