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

Keir, Derek; Bastow, I. D.; Pagli, Carolina; Chambers, Emma L.

doi:10.1016/j.tecto.2012.10.015

Cited by 81 publications

(87 citation statements)

References 164 publications

(243 reference statements)

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“…The modelling of its shape between 8.5 and 15 km depth is guided by the Euler deconvolution result. The broader interface between the magma reservoir and the surrounding rocks at 15.3 km is in good agreement with the geodetic estimates of the source depth of dykes intruded during the current magmatic episode in Afar (Hamling 2010;Keir et al 2013). The location of the magma reservoir is also consistent with the MT result (Johnson 2012).…”

supporting

confidence: 86%

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

Lewi

Keir

Birhanu

et al. 2015

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Abstract:The Red Sea arm of the triple junction in northeastern Ethiopia provides an opportunity to investigate rift-forming processes at divergent boundaries. In an attempt to study the subsurface, especially the distribution and role of melt in the rifting process, we carried out a high-precision gravity survey with a mean-square error of 0.011 mgal, assisted by differential global positioning system measurements. The profile is 162 km long and strikes ENE-WSW across the southern part of the Red Sea rift at a latitude of approximately 11.758 N. Modelling of the Bouguer anomaly, constrained by a priori information, showed detailed in-rift variations in the crustal structure and the distribution of melt beneath the rift axis. Our interpretation suggested that the process of continental break-up is governed by crustal stretching and rifting accompanied by the emplacement of melt into the lower crust above a lower density upper mantle. In addition, we interpreted the thickness of the crust beneath this part of the rift axis to be 25 km. The subsurface distribution of density beneath the profile shows that the south-central part of the Red Sea rift has modified thinned crust, intruded by high-density material, which resembles the crust formed during seafloor spreading.Gold Open Access: This article is published under the terms of the CC-BY 3.0 license.

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supporting

confidence: 86%

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

Lewi

Keir

Birhanu

et al. 2015

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“…Despite the logistical challenges of carrying out fieldwork in Afar, several decades of research underpin our current understanding of the regional volcanism and rifting (Ayele et al 2007(Ayele et al , 2009; Barberi et al 1974a, b;Ferguson et al 2010;Field et al 2012aField et al , b, 2013Hammond et al 2013Hammond et al , 2011Keir et al 2013Keir et al , 2011Lahitte et al 2003). Expeditions in the 1970s documented Afar volcanism at reconnaissance scale (Barberi et al 1974a(Barberi et al , b, 1970Civetta et al 1975).…”

Section: Regional Backgroundmentioning

confidence: 99%

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

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The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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“…1). Because of the low elevation, the surface sediments in the area largely consist of thick layers of evaporites formed from repeated marine incursions (Barberi and Varet, 1970;Keir et al, 2013), most recently 32,000 years ago (Bonatti et al, 1971). The depression also contains the NNW-SSE-trending Erta-Ale volcanic segment (EAVS) and seven active volcanoes (Barberi and Varet, 1970;Nobile et al, 2012;Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

Illsley‐Kemp¹,

Keir²,

Bull³

et al. 2017

Bulletin of the Seismological Society of America

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The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup. To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale. The accurate calculation of earthquake magnitudes allows the estimation of b-values and maximum magnitudes, both of which are essential for seismic-hazard analysis. Earthquake data collected between February 2011 and February 2013 on 11 three-component broadband seismometers were analyzed. A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km. A total of 32,904 zero-to-peak amplitude measurements (A) were measured on the seismometer's horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (M L ), 22 station correction factors (C), and 2 distance-dependent factors (n, K) in the equation M L logA− logA 0 C. The resultant distance correction term is given by − logA 0 1:274336 logr=17 − 0:000273r − 17 2. This distance correction term suggests that attenuation in the upper and mid-crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt. In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band. The calculated station corrections serve to reduce the M L residuals significantly but do not show a correlation with regional geology. The cumulative seismicity rate produces a b-value of 0:9 0:06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading.Electronic Supplement: List of all local earthquakes used in the study with calculated local magnitudes and associated magnitude error.

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

Cited by 81 publications

References 164 publications

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

Use of a high-precision gravity survey to understand the formation of oceanic crust and the role of melt at the southern Red Sea rift in Afar, Ethiopia

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

Local Earthquake Magnitude Scale andb‐Value for the Danakil Region of Northern Afar

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