Temporal compositional variation of syn-rift rhyolites along the western margin of the southern Red Sea and northern Main Ethiopian Rift

Ayalew, Dereje; Ebinger, C. J.; Bourdon, Erwan; Wolfenden, E.; Yirgu, Gezahegn; Grassineau, Nathalie

doi:10.1144/gsl.sp.2006.259.01.10

Cited by 42 publications

(41 citation statements)

References 42 publications

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“…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: 62%

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: 62%

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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“…1). Geochronological constraints in Ethiopia suggest rifting began 29-31 Ma on the western Afar margin (e.g., Ayalew et al, 2006;Wolfenden et al, 2005) ( Fig. 3), approximately coeval with~35 Ma faulting along large portions of the Gulf of Aden (Leroy et al, 2010) (Fig.…”

Section: Rift Initiationmentioning

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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“…Over time, the locus of faulting and magmatism migrated in riftward direction, finally forming the Quaternary magmatic segments ( Fig. 1) within the MER (Ayalew et al, 2006). Magmatosedimentary deposits of the surveyed MGF formed and suffered tectonic overprinting under this conditions in Pliocene to early Pleistocene times , what is specified in subsequent chapters below.…”

Section: Geological Settingmentioning

confidence: 95%

“…Beyene and Abdelsalam, 2005;Buck, 2006). Both are composed of continental flood basalts of a related magmatism predating continental break-up by several million years (Ayalew et al, 2006). The main tectonic elements of the region, i.e.…”

Section: Geological Settingmentioning

confidence: 99%

“…Within the contemporaneous MGF, diverse basalt layers show a trend from OIB (ocean island basalt) towards MORB (mid ocean ridge basalt) geochemical signatures, thus highlighting a magmato-tectonic setting between continental and oceanic rifting (Urbanek et al, 2005). Concerning the prominent felsic volcanism, generated from soaring rift faults, Ayalew et al (2006) reported that the felsic rocks, which erupted during the formation of the MER in the age range from 28 to 2.5 Ma, can be derived from mantle-sourced basaltic magma through fractional crystallization, accompanied by variable amounts of crustal contaminations. Within the MGF, a significant acidic volcanic marker bed (top of the Dhidinley Mb.)…”

Section: _____________________________________mentioning

confidence: 99%

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Paleomagnetic constraints on stratigraphy and rift-related tectonics of Pliocene and Early Pleistocene volcano-sedimentary strata: the Mt. Galili hominid research area, Southern Afar Depression, Ethiopia

Popp¹,

Scholger²

2018

AJES

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Our paleomagnetic investigations in the Northern Main Ethiopian Rift concentrated on ascertaining characteristic remanence directions of volcanic and sedimentary layers embodied within the Mt.Galili Formation (MGF). Magnetic stratigraphy was applied mainly to support anthropological studies on early hominid evolution. The new paleomagnetic results provided implications for stratigraphic age determinations of the MGF, and they also support arguments for rift-related tectonics as block rotation and tilting relative to the stable African crust since the Pliocene.Based on 497 paleomagnetic samples, we applied magnetic stratigraphy on magmatic and sedimentary rocks to determine the 39age of the MGF and correlated the results with published Ar/ Ar age data on tuff and ignimbrite layers which range from ca. 5.4 Ma to ca. 2.3 Ma, consistent with biostratigraphic age constraints. Nine magnetic polarity intervals of the Gilbert zone were identified within the lower four members of the MGF covering a time span from 5.37 to 3.58 Ma. The upper two members of the MGF comprised three polarity intervals assigned to the upper Gauss and lower Matuyama polarity zones. In combination with an 39Ar/ Ar age of 2.35 Ma, located in the middle of the section, we infer that ca. 0.5 Ma and four polarity intervals are missing between the MGF's lower and upper members. We attribute this significant depositional gap to uplift of the region due to the intrusion of basalt magma, associated with deposition of the Upper Shabeley Laag Member.Extensional rift tectonic processes were intimately affiliated with magmatic activity and generation of rapidly changing sedimentary environments of the MGF`s deposits, but the bulk of the observed tectonic features resulted from post-depositional tectonic overprint, when the re-orientated Wonji Fault System affected the Mt.Galili area in the Quaternary period, thereby creating new internal rift (in older rift) structures. Tectonic movements of MGF`s strata were deduced from our analysed characteristic remanent magnetisation (ChRM) directions compared with Pliocene reference data. The investigation revealed almost unchanged orientation of the ChRM-directions for the marginal internal rift zone in the East of the Mt.Galili area, but moderate counterclockwise rotation for the central internal rift zone in the West. The North of the Mt.Galili area suffered moderate clockwise rotation, probably due to the Mt.Galili area`s regional position, adjoining a transfer zone between the Quaternary Angele and Addo-Do magmatic segments.

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Temporal compositional variation of syn-rift rhyolites along the western margin of the southern Red Sea and northern Main Ethiopian Rift

Cited by 42 publications

References 42 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

Paleomagnetic constraints on stratigraphy and rift-related tectonics of Pliocene and Early Pleistocene volcano-sedimentary strata: the Mt. Galili hominid research area, Southern Afar Depression, Ethiopia

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