Strain accommodation in transitional rifts: extension by magma intrusion and faulting in Ethiopian rift magmatic segments

Casey, Martin; Ebinger, C. J.; Keir, Derek; Gloaguen, Richard; Mohamed, F.H.

doi:10.1144/gsl.sp.2006.259.01.13

Cited by 119 publications

(174 citation statements)

References 69 publications

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“…We use the along-axis segmentation interpretations of Casey et al (2006) to construct 2-D mapview and cross-sectional finite element models of the MER with varying strength magmatic intrusive bodies. The stress field generated under the various modeled conditions is calculated with the elastic finite element code of Gobat and Atkinson (1999).…”

Section: Methodsmentioning

confidence: 99%

“…1 and 2). Silicic volcanic complexes are located at the tips of the en echelon magmatic segments in the Main Ethiopian Rift (Wolfenden et al, 2005;Casey et al, 2006) (Fig. 2).…”

Section: Magmatic Segments In the Northern Mer And Southern Red Sea Rmentioning

confidence: 99%

“…4), volcanoes were also added as loads to the top of the plate. The size and distribution of the magmatic bodies and volcanoes were taken from Cornwell et al (2006) and Casey et al (2006).…”

Section: Evolution Of Magmatic Segmentsmentioning

confidence: 99%

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Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts

Beutel

Wijk

Ebinger

et al. 2010

Earth and Planetary Science Letters

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Editor: R.D. van der HilstKeywords: East African Rift continental rifting magmatic intrusion stress lithospheric extension rupturing continental lithosphere As rifting progresses to seafloor spreading, extension within the continental crust commonly is accommodated by a combination of fault slip and dike intrusion. Consistent patterns in the spatial arrangement of long-lived magma intrusion zones in the Ethiopian and Afar rift sectors, East Africa, suggest that the magma intrusions help to localize strain during repeated rifting episodes. Within the broad Main Ethiopian Rift, extensional deformation has localized since ∼ 3 m.y. in narrow magmatic segments, that are oriented oblique to the orientation of the Miocene border faults, but (sub-) orthogonal to the extension direction. Numerical models combined with geophysical and geological observations from East Africa are used to examine the viability of self-sustaining magmatic segmentation. Initiation of the magmatic segments is shown to result from magma injections, which focus strain in narrow elongated zones. During magmatic phases of segment evolution the segments are weak, and extensional stresses localize at the rift tips, promoting along-axis lengthening. During amagmatic phases of extension, the numerical models predict strain localization within the magmatic segments and, to a lesser extent, broadly distributed extension within the rift zone. This promotes segment stability; the segments remain the preferred location for magma intrusion during new magmatic phases. These results are applied to the formation and maintenance of MER segmentation. The Fentale-Dofen segment is currently in a non-magmatic phase of extension; the Dabbahu segment in the Red Sea Rift is currently experiencing a rifting episode and therefore is in a transient magmatic cycle. The observed patterns of instantaneous localized deformation, seismicity, and dike intrusions sometimes propagating beyond the tip of the magmatic segments occur as predicted by the models.

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Section: Methodsmentioning

confidence: 99%

“…1 and 2). Silicic volcanic complexes are located at the tips of the en echelon magmatic segments in the Main Ethiopian Rift (Wolfenden et al, 2005;Casey et al, 2006) (Fig. 2).…”

Section: Magmatic Segments In the Northern Mer And Southern Red Sea Rmentioning

confidence: 99%

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Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts

Beutel

Wijk

Ebinger

et al. 2010

Earth and Planetary Science Letters

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“…In the third and final stage of rift development, extension became focused at the rift axis (Mohr, 1978;Bilham et al, 1999;Ebinger and Casey, 2001;Casey et al, 2006;Rooney et al, 2011), manifested as intensive diking through severely thinned lithosphere (Ebinger and Casey, 2001; Fig. 11.…”

Section: Stage 3: Strain Accommodation By Magmatic Intrusionmentioning

confidence: 99%

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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“…The Quaternary rifting and volcanism still exerts a strong control on surface morphology [18][19][20]. The shallow and saline lake is located about 126 km west of Arusha, Northern Tanzania (3°25'-3°48'S, 35°44'-35°53'E, 960 m a.s.l., Figure 1).…”

Section: Settingmentioning

confidence: 99%

Water Balance Modeling in a Semi-Arid Environment with Limited in situ Data Using Remote Sensing in Lake Manyara, East African Rift, Tanzania

2013

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Abstract:The purpose of this paper is to estimate the water balance in a semi-arid environment with limited in situ data using a remote sensing approach. We focus on the Lake Manyara catchment, located within the East African Rift of northern Tanzania. We use a distributed conceptual hydrological model driven by remote sensing data to study the spatial and temporal variability of water balance parameters within the catchment. Satellite gravimetry GRACE data is used to verify the trends of the inferred lake level changes. The results show that the lake undergoes high spatial and temporal variations, characteristic of a semi-arid climate with high evaporation and low rainfall. We observe that the Lake Manyara water balance and GRACE equivalent water depth show comparable trends; a 1652Despite the small size of Lake Manyara, GRACE data showed great potential for hydrological research on smaller un-gauged lakes and catchments in similar semi-arid environments worldwide. The water balance information can be used for further analysis of lake variations in relation to soil erosion, climate and land cover/land use change as well as different lake management and conservation scenarios.

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Strain accommodation in transitional rifts: extension by magma intrusion and faulting in Ethiopian rift magmatic segments

Cited by 119 publications

References 69 publications

Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts

Formation and stability of magmatic segments in the Main Ethiopian and Afar rifts

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

Water Balance Modeling in a Semi-Arid Environment with Limited in situ Data Using Remote Sensing in Lake Manyara, East African Rift, Tanzania

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