Northern Main Ethiopian Rift crustal structure from new high-precision gravity data

Cornwell, David G.; Mackenzie, G. D.; England, Richard; Maguire, P. K. H.; Asfaw, Laike M.; Oluma, Befekadu

doi:10.1144/gsl.sp.2006.259.01.23

Cited by 74 publications

(129 citation statements)

References 52 publications

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“…Up to 25% of the crust beneath the northern MER and Afar depression is new igneous material, but with minor amounts of crustal stretching south of Fentale volcano (9°N; Figs. 2 and 3) (Mackenzie et al, 2005;Tiberi et al, 2005;Dugda et al, 2005;Cornwell et al, 2006). Ayalew et al (2006) interpreted systematic changes in the chemistry of felsic lavas as increasing amounts of crustal melting over the period 31 Ma to present, consistent with the spatial localization of strain.…”

Section: Tectonic Settingmentioning

confidence: 70%

“…On the boundaries we applied forces in the N105°E direction that were based on the far-field motion of the East African Rift and present day stress calculations (Fernandes et al, 2004;Bilham et al, 1999). Physical properties of the elements in the rift that we used are from Cornwell et al (2006), Mackenzie et al (2005), Tiberi et al (2005), and Tessema and Antoine (2004) (Table 1).…”

Section: Methodsmentioning

confidence: 99%

“…Tomographic images reveal an along-axis segmentation in crustal seismic velocity patterns beneath the magmatic segments. The magmatic segments are characterised by positive Bouguer anomalies (Tessema and Antoine, 2004;Tiberi et al, 2005;Cornwell et al, 2006) and underlain by anomalously high velocity material interpreted as cooled mafic intrusions (Keranen et al, 2004;Daly et al, 2008). Keranen et al (2004) and Daly et al (2008) tomographically imaged a right-stepping pattern of high velocities between 20 km and 7 km depth in the crust beneath magmatic segments.…”

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: Tectonic Settingmentioning

confidence: 70%

Section: Methodsmentioning

confidence: 99%

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

confidence: 99%

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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“…2) (e.g., Agostini et al, 2011a,b;Corti, 2008Corti, , 2009Hayward and Ebinger, 1996;Keir et al, 2011a). In the MER, gravity and seismic imaging show that magmatic segments are underlain by dense, high seismic velocity material, interpreted as cooled gabbroic intrusions (e.g., Beutel et al, 2010;Cornwell et al, 2006;Keranen et al, 2004;Mackenzie et al, 2005;Maguire et al, 2006). Since the voluminous intrusions into the mid-upper crust appear largely restricted to beneath the Quaternary-Recent magmatic segments, it is likely that magma intrusion has only dominated extension during the past~2 Ma (Daly et al, 2008;Keranen et al, 2004).…”

Section: Localisation Of Strainmentioning

confidence: 99%

The development of extension and magmatism in the Red Sea rift of Afar

et al. 2013

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Despite the importance of continental breakup in plate tectonics, precisely how extensional processes such as brittle faulting, ductile plate stretching, and magma intrusion evolve in space and time during the development of new ocean basins remains poorly understood. The rifting of Arabia from Africa in the Afar depression is an ideal natural laboratory to address this problem since the region exposes subaerially the tectonically active transition from continental rifting to incipient seafloor spreading. We review recent constraints on along-axis variations in rift morphology, crustal and mantle structure, the distribution and style of ongoing faulting, subsurface magmatism and surface volcanism in the Red Sea rift of Afar to understand processes ultimately responsible for the formation of magmatic rifted continental margins. Our synthesis shows that there is a fundamental change in rift morphology from central Afar northward into the Danakil depression, spatially coincident with marked thinning of the crust, an increase in the volume of young basalt flows, and subsidence of the land towards and below sea-level. The variations can be attributed to a northward increase in proportion of extension by ductile plate stretching at the expense of magma intrusion. This is likely in response to a longer history of localised heating and weakening in a narrower rift. Thus, although magma intrusion accommodates strain for a protracted period during rift development, the final stages of breakup are dominated by a phase of plate stretching with a shift from intrusive to extrusive magmatism. This late-stage pulse of decompression melting due to plate thinning may be responsible for the formation of seaward dipping reflector sequences of basalts and sediments, which are ubiquitous at magmatic rifted margins worldwide.

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Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

et al. 2014

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The Afar Depression is an ideal locale for the investigation of crustal processes involved in the transition from continental rifting to oceanic spreading. To provide relatively high resolution images of the crust beneath the Red Sea rift (RSR) represented by the Tendaho graben in the Afar Depression, we deployed an array of 18 broadband seismic stations in 2010 and 2011. Stacking of about 2300 receiver functions from the 18 and several nearby stations along the ∼200 km long array reveals an average crustal thickness of 22 ± 4 km, ranging from ∼17 km near the RSR axis to 30 km within the overlap zone between the Red Sea and Gulf of Aden rifts. The resulting anomalously high V p ∕V s ratios decrease from 2.40 in the southwest to 1.85 within the overlap zone. We utilize theoretical V p and melt fraction relationships to obtain an overall highly reduced average crustal V p of ∼5.1 km/s. The melt percentage is about 10% beneath the RSR while the overlap zone contains minor quantities of partial melt. The observed high V p ∕V s values beneath most of the study area indicate widespread partial melting beneath the southwest half of the profile, probably as a result of gradual eastward migration of the RSR axis. Our results also suggest that the current extensional strain in the lower crust beneath the region is diffuse, while the strain field in the upper crust is localized along narrow volcanic segments. These disparate styles of deformation imply a high degree of decoupling between the upper and lower crust.

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Northern Main Ethiopian Rift crustal structure from new high-precision gravity data

Cited by 74 publications

References 52 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

The development of extension and magmatism in the Red Sea rift of Afar

Receiver function constraints on crustal seismic velocities and partial melting beneath the Red Sea rift and adjacent regions, Afar Depression

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