Dike‐fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia)

Nobile, Adriano; Pagli, Carolina; Keir, Derek; Wright, Tim; Ayele, Atalay; Ruch, J.; Acocella, Valerio

doi:10.1029/2012gl053152

Cited by 93 publications

(135 citation statements)

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“…At Erta Ale, the two active craters sit within a~3 km-long,~1 km-wide,~NNW elongate caldera (Acocella, 2006), a geometry consistent with the caldera forming after removal of magma from a shallow axial sill similar in shape and depth to that at Alu-Dallafilla. In northernmost Afar, modelling of deformation during October 2004 shows evidence that magma intruded into the rift axis was sourced from a reservoir located 2 km beneath Dallol (Nobile et al, 2012). These observations along the Erta Ale range provide strong evidence that portions of the rift axis are underlain by relatively long-lived shallow pockets of magma similar to the shallow axial sills mainly found beneath intermediate-to fast-spreading mid ocean ridges .…”

Section: -2010 Basaltic Eruptions In the Erta'ale Rangementioning

confidence: 66%

“…This adds support to the view that mechanical deformation via mechanical extension (plate stretching and faulting) currently accounts for a higher proportion of lithospheric strain in the Danakil depression than further south in the MHR and TG, where dike intrusion dominates. In addition, the proximity of rift margin border faults to the volcanic axis (in northern-most Afar in particular) may result in close interaction between faulting near the rift margins and magmatic processes nearer to the rift centre (e.g., Nobile et al, 2012;Ogubazghi et al, 2004).…”

Section: Links Between Extension Magmatism and Rift Morphologymentioning

confidence: 99%

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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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Section: -2010 Basaltic Eruptions In the Erta'ale Rangementioning

confidence: 66%

Section: Links Between Extension Magmatism and Rift Morphologymentioning

confidence: 99%

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

et al. 2013

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“…0.2 Tg of SO 2 was released in the troposphere (Carboni et al, 2015). Four years before this, in October 2004, an intruding dyke at Dallol on the extreme northern tip of the Erta Ale segment, 50 km NNW of Alu-Dalafilla, was revealed by InSAR (Nobile et al, 2012). This dyke was 9 km long, striking 155 • (c.f.…”

Section: Alu-dalafilla (2008)mentioning

confidence: 99%

Historical Volcanism and the State of Stress in the East African Rift System

et al. 2016

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Crustal extension at the East African Rift System (EARS) should, as a tectonic ideal, involve a stress field in which the direction of minimum horizontal stress is perpendicular to the rift. A volcano in such a setting should produce dykes and fissures parallel to the rift. How closely do the volcanoes of the EARS follow this? We answer this question by studying the 21 volcanoes that have erupted historically (since about 1800) and find that 7 match the (approximate) geometrical ideal. At the other 14 volcanoes the orientation of the eruptive fissures/dykes and/or the axes of the host rift segments are oblique to the ideal values. To explain the eruptions at these volcanoes we invoke local (non-plate tectonic) variations of the stress field caused by: crustal heterogeneities and anisotropies (dominated by NW structures in the Protoerozoic basement), transfer zone tectonics at the ends of offset rift segments, gravitational loading by the volcanic edifice (typically those with 1-2 km relief) and magmatic pressure in central reservoirs. We find that the more oblique volcanoes tend to have large edifices, large eruptive volumes, and evolved and mixed magmas capable of explosive behavior. Nine of the volcanoes have calderas of varying ellipticity, 6 of which are large, reservoir-collapse types mainly elongated across rift (e.g., Kone) and 3 are smaller, elongated parallel to the rift and contain active lava lakes (e.g., Erta Ale), suggesting different mechanisms of formation and stress fields. Nyamuragira is the only EARS volcano with enough sufficiently well-documented eruptions to infer its long-term dynamic behavior. Eruptions within 7 km of the volcano are of relatively short duration (<100 days), but eruptions with more distal fissures tend to have lesser obliquity and longer durations, indicating a changing stress field away from the volcano. There were major changes in long-term magma extrusion rates in 1977 (and perhaps in 2002) due to major along-rift dyking events that effectively changed the Nyamuragira stress field and the intrusion/extrusion ratios of eruptions.

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“…In more evolved rifts where protracted intrusion has significantly heated the plate, such as in Afar, <10-km-deep magma reservoirs beneath axial volcanoes are common 25,26 and feed episodic dykes along the axis 4,27 .…”

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Off-rift volcanism in rift zones determined by crustal unloading

et al. 2014

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When continents are stretched over a long period of time, deep elongated rift valleys form at Earth's surface and zones of ponded magma, centred beneath the rift, form at the crust-mantle boundary 1,2 . Ascending magma sometimes erupts within the rift valley 3,4 or, counterintuitively, at volcanic fields away from the rift valley that are o set by tens of kilometres from the source of magma at depth 5-8 . The controls on the distribution of this o -rift volcanism are unclear. Here we use a numerical model of magmatic dyke propagation during rifting to investigate why some dykes reach the surface outside the rift valley, whereas others are confined to the valley. We find that the location of magmatism is governed by the competition between tectonic stretching and gravitational unloading pressure, caused by crustal thinning and faulting along the rift borders. When gravitational unloading dominates over tectonic stretching forces, dykes ascending from the ponded magma are steered towards the rift sides, eventually causing o -rift eruptions. Our model also predicts the formation of stacked magma sills in the lower crust above the magma-ponding zone, as well as the along-rift propagation of shallow dykes during rifting events, consistent with observations of magmatism and volcanism in rift zones globally. We conclude that rift topography-induced stress changes provide a fundamental control on the transfer of magma from depth to the surface.Continental rifts are commonly flanked by magmatism during their early stages 5,6 . In the Miocene-Recent Main Ethiopian Rift (MER), for example, many Pliocene volcanoes lie outside the Miocene rift border faults 9,10 ( Fig. 1). As the cumulative extension has increased, magmatism has become focused within the rift axis 3 . A similar pattern is observed during the evolution of the Red Sea Rift, where ∼25-Myr-old rift-parallel dykes focus near the ∼30-Myr-old rift margins and the youngest volcanoes focus along the ridge axis 11 . Even in far less magmatically active settings, such as the Baikal Rift (Siberia) or the Chaine des Puys (CdP) in the Cenozoic rift system of France, off-rift volcanism occurred after the onset of rifting 7,8 .During rift initiation, the lithosphere thins by ductile stretching beneath a rift valley formed from normal faulting 12 . The upwelling asthenosphere melts by adiabatic decompression, with the greatest degree of partial melting beneath the most thinned rift valley 1,2 . Although most studies focus on in-rift magmatism 3,4 , a model is needed to explain how off-rift volcanoes are fed. Progressive rift spreading results in the oldest volcanoes being transported away from the rift axis. However, such a process does not explain off-rift volcanism, with volcanoes located outside the rift border faults. Previous models for off-rift volcanoes include low-angle detachments tapping the asthenosphere to the sides of highly asymmetric rifts 13 , or the flexural response at the base of the footwall of the active rift border faults 5 . These models are unsatisfac...

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Dike‐fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia)

Cited by 93 publications

References 40 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

Historical Volcanism and the State of Stress in the East African Rift System

Off-rift volcanism in rift zones determined by crustal unloading

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