The nature of the crust beneath the Afar triple junction: Evidence from receiver functions

Hammond, James; Kendall, J.‐M.; Stuart, G. W.; Keir, Derek; Ebinger, C. J.; Ayele, Atalay; Belachew, M.

doi:10.1029/2011gc003738

Cited by 171 publications

(386 citation statements)

References 94 publications

(255 reference statements)

Supporting

Mentioning

338

Contrasting

Order By: Relevance

“…Discussion has often focussed on whether the crust is completely new oceanic crust, or whether it is stretched and thinned continental crust, heavily intruded by magma (transitional crust). Constraints on crustal structure primarily come from wide-angle seismic studies (Berckhemer et al, 1975;Maguire et al, 2006;Makris and Ginzburg, 1987;Prodehl et al, 1997), teleseismic receiver function studies (Ayele et al, 2004;Dugda et al, 2005;Hammond et al, 2011;Stuart et al, 2006), and from gravity analysis (Redfield et al, 2003;Tessema and Antoine, 2004;Tiberi et al, 2005). Results achieved using these different methods are broadly consistent (e.g., Fishwick and Bastow, 2011).…”

Section: Crustal Structurementioning

confidence: 68%

“…The structure and composition of the crust beneath Afar have been the subject of much debate during the last~35 years (e.g., Berckhemer et al, 1975;Hammond et al, 2011;Makris and Ginzburg, 1987;Mohr, 1970Mohr, , 1989. Discussion has often focussed on whether the crust is completely new oceanic crust, or whether it is stretched and thinned continental crust, heavily intruded by magma (transitional crust).…”

Section: Crustal Structurementioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2013

View full text Add to dashboard Cite

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.

show abstract

Section: Crustal Structurementioning

confidence: 68%

Section: Crustal Structurementioning

confidence: 99%

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

et al. 2013

View full text Add to dashboard Cite

show abstract

“…More recent studies of the Afar region and Ethiopian Rift Valley have revealed physical and chemical heterogeneity [e.g., (Ebinger et al 2010;Ebinger and Sleep 1998;Furman et al 2006;Keir et al 2011;Pik et al 2008Pik et al , 2006 Rooney et al 2012a]; Hammond et al (2011) showed that there is a considerable variation in Moho depth across Afar, even within the central rift area. Their study area does not quite reach the Bidu Massif, but points to a crust thickness of about 20 km in the region of the Danakil Horst (Fig.…”

Section: Regional Backgroundmentioning

confidence: 99%

“…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 melt inclusions can be modelled by a combination of isobaric crystallisation and closed-system degassing during ascent. It is likely that they represent two or more batches of melt sourced from a single and relatively homogeneous melt zone in the uppermost mantle (~ 20 km depth; Hammond et al 2011), inferred on the basis of mineralogy and sulphur content. Melts ascending through the crust may crystallise through decompression, once water saturation is attained, or stall and crystallise by cooling.…”

Section: Magma Storage Depths and Plumbing System At Nabromentioning

confidence: 99%

See 1 more Smart Citation

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

Donovan

Blundy

Oppenheimer

et al. 2017

Contrib Mineral Petrol

View full text Add to dashboard Cite

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.

show abstract

Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia

Hammond¹,

Kendall

Wookey

et al. 2014

Geochem Geophys Geosyst

Self Cite

View full text Add to dashboard Cite

Ethiopia is a region where continental rifting gives way to oceanic spreading. Yet the role that pre-existing lithospheric structure, melt, mantle flow, or active upwellings may play in this process is debated. Measurements of seismic anisotropy are often used to attempt to understand the contribution that these mechanisms may play. In this study, we use new data in Afar, Ethiopia along with legacy data across Ethiopia, Djibouti, and Yemen to obtain estimates of mantle anisotropy using SKS-wave splitting. We show that two layers of anisotropy exist, and we directly invert for these. We show that fossil anisotropy with fast directions oriented northeast-southwest may be preserved in the lithosphere away from the rift. Beneath the Main Ethiopian Rift and parts of Afar, anisotropy due to shear segregated melt along sharp changes in lithospheric thickness dominates the shear-wave splitting signal in the mantle. Beneath Afar, away from regions with significant lithospheric topography, melt pockets associated with the crustal and uppermost mantle magma storage dominate the signal in localized regions. In general, little anisotropy is seen in the uppermost mantle beneath Afar suggesting melt retains no preferential alignment. These results show the important role melt plays in weakening the lithosphere and imply that as rifting evolves passive upwelling sustains extension. A dominant northeast-southwest anisotropic fast direction is observed in a deeper layer across all of Ethiopia. This suggests that a conduit like plume is lacking beneath Afar today, rather a broad flow from the southwest dominates flow in the upper mantle.

show abstract

The nature of the crust beneath the Afar triple junction: Evidence from receiver functions

Cited by 171 publications

References 94 publications

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

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

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

Differentiating flow, melt, or fossil seismic anisotropy beneath Ethiopia

Contact Info

Product

Resources

About