Evidence for focused magmatic accretion at segment centers from lateral dike injections captured beneath the Red Sea rift in Afar

Keir, Derek; Hamling, I. J.; Ayele, Atalay; Calais, E.; Ebinger, C. J.; Wright, Tim; Jacques, Éric; Mohamed, K.; Hammond, James; Belachew, M.; Baker, Elizabeth; Rowland, J. V.; Lewi, Elias; Bennati, Laura

doi:10.1130/g25147a.1

Cited by 148 publications

(178 citation statements)

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“…Along the rift axis the graben is disrupted by the volcanic topography associated with the Ado Ale Volcanic complex (AVC), a series of faulted silicic lavas flows/domes on the rift flanks and a basaltic volcano at the rift axis with a summit crater, and at its northern end the Dabbahu volcano, which has been active since at least B80 ka (refs 25 and (S. Medynski personal communication)). Seismic [11][12][13] and geodetic [14][15][16][17] observations of the recent dyking events are consistent with a magma source located in the rift centre below the AVC. This central volcanic region also marks a division in the width and morphology of the axial graben and rift flanks between the southern (graben B8 km wide, scarps B100 m high, significant flank topography) and northern (graben B4 km wide, scarps B30-50 m high, smooth flank profile) sectors (Fig.…”

Section: Discussionsupporting

confidence: 56%

“…Observations of the multiple (B14) dyke intrusions 3,[11][12][13][14][15][16][17] and fissure eruptions 18 during this active phase have shown that in the upper part of the crust, the delivery of melts to the DMH rift zone is currently strongly focused along the rift axis. The overall scale and morphology of this B15 Â 60 km magmatic segment is similar to a slow (B20 mm per year) spreading mid-ocean-ridge segment 6 , such as those found along the Mid-Atlantic ridge 19,20 , and the recent episodic rifting activity is similar to that previously observed in Iceland 4,21 .…”

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Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

et al. 2013

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As continental rift zones mature the tectonic and volcanic processes associated with crustal extension become confined to narrow magmatic rift zones, reminiscent of oceanic spreading ridges. The formation of these rift zones and the development of ocean-ridge type topography is a significant milestone in rift evolution as it signifies the localization of crustal extension and rift-related volcanism. Here we show that lavas, which erupted since B200 ka along part of the on-land Red Sea rift system in Afar, Ethiopia, have a consistent age-progression from the rift axis outwards, indicating that axial dyke intrusion has been the primary mechanism of segment growth and that focused magmatic accretion and extension in the crust have remained stable here over this period. Our results suggest that as this rift segment has formed, in thinned and intruded continental crust, the time-averaged surface opening rate has closely approximated the total extension rate between Africa and Arabia.

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Section: Discussionsupporting

confidence: 56%

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confidence: 99%

Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

et al. 2013

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“…These dykes are typically 1-3 m thick, 10-15 km long, and have a cumulative volume of 1 km 3 (Grandin et al, 2010;Hamling et al, 2009). Seismicity data show that they were all fed from the AVC and propagated at rates of 0.2-0.6 m/s Grandin et al, 2011;Keir et al, 2009b). As was the case during the September 2005 intrusion, dike-induced faulting accompanied intrusion but made a relatively minor contribution to the total deformation.…”

Section: The 2005-2011 Dabbahu-manda-harraro Rifting Episodementioning

confidence: 95%

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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“…This has often been observed during dike intrusions, for instance in Afar in 2006 [Grandin et al, 2009;Keir et al, 2009], at the volcanic island of Izu in 2000 [Nishimura et al, 2001] or during the 2007 Natron faulting and diking event [Baer et al, 2008;Calais et al, 2008;Biggs et al, 2009]. Large earthquakes, such as the 3 February 2002 5.9 M w Bukavu event [d 'Oreye et al, 2011], or the October 24, 2002 6.2 M w south Lake Kivu event ( Figure S8 in the auxiliary material), might remain undetected by interferometry if they were to occur beneath Lake Kivu or in areas of low coherence.…”

Section: Eruption Modelmentioning

confidence: 99%

“…Therefore, compared to better-studied rifting events, such as the Manda-Hararo 2005-2010 diking events [Keir et al, 2009;Grandin et al, 2010] or the Puu' Oo 1983 eruption [Rubin et al, 1998], it is not possible to detect if the deep dike was fed by a mid-segment reservoir.…”

Section: Eruption Modelmentioning

confidence: 99%

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

Wauthier¹,

Cayol²,

Kervyn³

et al. 2012

J. Geophys. Res.

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along a 20 km-long fracture network extending from the volcano to the city of Goma. The event was captured by InSAR data from the ERS-2 and RADARSAT-1 satellites. A combination of 3D numerical modeling and inversions is used to analyze these displacements. Using Akaike Information Criteria, we determine that a model with two subvertical dikes is the most likely explanation for the 2002 InSAR deformation signal. A first, shallow dike, 2 km high, is associated with the eruptive fissure, and a second, deeper dike, 6 km high and 40 km long, lies about 3 km below the city of Goma. As the deep dike extends laterally for 20 km beneath the gas-rich Lake Kivu, the interaction of magma and dissolved gas should be considered as a significant hazard for future eruptions. A likely scenario for the eruption is that the magma supply to a deep reservoir started ten months before the eruption, as indicated by LP events and tremor. Stress analysis indicates that the deep dike could have triggered the injection of magma from the lake and shallow reservoir into the eruptive dike. The deep dike induced the opening of the southern part of this shallow dike, to which it transmitted magma though a narrow dike. This model is consistent with the geochemical analysis, the lava rheology and the pre-and post-eruptive seismicity. We infer low overpressures (1-10 MPa) for the dikes. These values are consistent with lithostatic crustal stresses close to the dikes and low magma pressure. As a consequence, the dike direction is probably not controlled by stresses but rather by a reduced tensile strength, inherited from previous rift intrusions. The lithostatic stresses indicate that magmatic activity is intense enough to relax tensional stresses associated with the rift extension.

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Evidence for focused magmatic accretion at segment centers from lateral dike injections captured beneath the Red Sea rift in Afar

Cited by 148 publications

References 28 publications

Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

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

Magma sources involved in the 2002 Nyiragongo eruption, as inferred from an InSAR analysis

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