Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

Pallister, John S.; McCausland, Wendy; Jónsson, Sigurjón; Lü, Zhong; Zahran, Hani; Hadidy, Salah El; Aburukbah, Abdallah; Stewart, Ian; Lundgren, P.; White, Randal A.; Moufti, Mohammed Rashad

doi:10.1038/ngeo966

Cited by 195 publications

(179 citation statements)

References 35 publications

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“…Our model is also consistent with observations of subvertical dykes feeding off-rift volcanism and ∼20-25-Myr-old basaltic dyke swarms along the Red Sea Rift margin 28 , which are thought to accommodate strain after the onset of rifting 29-31 Myr ago 11,29 . In contrast, rifts with mild topographic expression (wide and shallow depression), such as the NVZ, lack significant off-rift volcanism.…”

supporting

confidence: 89%

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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supporting

confidence: 89%

Off-rift volcanism in rift zones determined by crustal unloading

et al. 2014

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“…Moreover, we do not have a good a priori knowledge of the host rock stress, thus, of the overpressure. Using a constant stress model for dikes leads to a smoothly varying opening on the fracture [Cayol and Cornet, 1997], consistent with results obtained from linear kinematic inversions of opening distributions [Yun et al, 2006;Pallister et al, 2010]. We invert the dike and fault geometries simultaneously with uniform stress vectors, leading to a minimum of 7 parameters per structure.…”

Section: Three-dimensional Boundary Element Modelingsupporting

confidence: 78%

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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“…H 2 O part of the fluid may be a product of dehydration of crustal material during metamorphism. However, no gas emissions or explosions were reported at Lunayyir (Pallister et al 2010). The high b-value around the dyke intrusion zone (b 4 1.3) also made its contribution of fluids to ruptures and the high rate in pore creation by fault slips as per swarm generation mechanism proposed by Yamashita (1999).…”

Section: Proposed Model For the Al-ays Earthquake Swarmmentioning

confidence: 97%

“…Since 2007, recording of periodic small earthquake swarms in the area prompted the Saudi Geological Survey (SGS) to fix a network of broadband seismometers surrounding the volcanic field with real-time *Corresponding author. Email: basabmukhopadhyay@yahoo.com A joint SGS-USGS study accompanied by geologic, geodetic and seismic surveys confirmed the volcanic nature of the swarm activity and registered some salient seismotectonic observations (Zahran et al 2009;Pallister et al 2010) that are summarized below:…”

Section: Introductionmentioning

confidence: 94%

“…. Tectonic models are offered that produced the Al-Ays swarm: (1) Stalled eruption or dyke intrusion (Zahran et al 2009), (2) Rift-related extension recorded by dyke intrusion (Pallister et al 2010), (3) Distant lithospheric flow away from the Red Sea trough beneath the Al-Ays (Ebinger and Blachew 2010) and (4) dyke intrusion and opening of volcanic rift inferred from InSAR measurements and elastic modelling (Baer and Hamiel 2010).…”

Section: Introductionmentioning

confidence: 99%

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Incipient status of dyke intrusion in top crust – evidences from the Al-Ays 2009 earthquake swarm, Harrat Lunayyir, SW Saudi Arabia

Mukhopadhyay

Mogren

Mukhopadhyay

et al. 2013

Geomatics, Natural Hazards and Risk

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The 2009 earthquake-swarm in the Al-Ays volcanic zone in Harrat-Lunayyir in NW Saudi-Arabia is unique because of its intense character and focal-depth distribution at two depth bands (5-10 and 15-20 km) in upper crust without volcanic eruption. We investigate an anatomy of the dyke-intrusion model that supports the mechanism for the swarm itself with seismotectonics, pore pressure diffusion process and inference model. Inferred dyke-intrusion initially started at depth had a five-day peak period (15-20 May 2009) since inception of eventrecordings, following which the activity diminished. The process of pore pressure perturbation and resultant ''r-t plot'' with modelled diffusivity (D ¼ 0.01) relates the diffusion of pore pressure to seismic sequence in a fractured poro-elastic fluidsaturated medium. The spatio-temporal b-values show high b-values (41.3) along the zone of dyke intrusion (length 10 km and height 5 km) at *20km depth. The main-shock and other prominent earthquakes originated on a moderate b-value zone (*1.0). Temporal b-value analysis indicates an exceptionally low b-value (*0.4) during the main-shock occurrence. The AlAys lava-field is inferred to underlie a seismic volume trending NW-SE bounded on both sides by two NW-SE trending fault systems, dipping 40-508 opposite to each other within a proposed nascent rift setting.

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Broad accommodation of rift-related extension recorded by dyke intrusion in Saudi Arabia

Cited by 195 publications

References 35 publications

Off-rift volcanism in rift zones determined by crustal unloading

Off-rift volcanism in rift zones determined by crustal unloading

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

Incipient status of dyke intrusion in top crust – evidences from the Al-Ays 2009 earthquake swarm, Harrat Lunayyir, SW Saudi Arabia

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