Insights into extensional processes during magma assisted rifting: Evidence from aligned scoria cones

Rooney, Tyrone O.; Bastow, I. D.; Keir, Derek

doi:10.1016/j.jvolgeores.2010.07.019

Cited by 88 publications

(142 citation statements)

References 147 publications

(316 reference statements)

Supporting

Mentioning

130

Contrasting

Order By: Relevance

“…9 and 10). Silicic volcanism is rare, with the basalt-rich geology indicating that parental magmas are stored for shorter periods in the crust prior to eruption (e.g., Rooney et al, 2007Rooney et al, , 2011. The relatively long-lived, shallow pockets of magma beneath the Danakil rift axis are reminiscent of the shallow axial sills found beneath intermediate-to-fast spreading ocean ridges .…”

Section: Implications For Magma Generation and The Formation Of Seawamentioning

confidence: 99%

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

et al. 2013

Self Cite

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: Implications For Magma Generation and The Formation Of Seawamentioning

confidence: 99%

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

et al. 2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…At the northern end of the EARS, the volcanically active Main Ethiopian Rift (MER) records the transition from continental rifting to seafloor spreading in the Red Sea and Gulf of Aden (Hayward and Ebinger, 1996;Ebinger and Casey, 2001;Bonini et al, 2005;Corti, 2009;Agostini et al, 2011a). The rift valley in the MER separates the Ethiopian and Somalian plateaus, which are capped with Eocene-Oligocene flood basalts, isolated OligoceneMiocene shield volcanoes and Quaternary scoria cone fields (Kieffer et al, 2004;Rooney et al, 2011). The MER is a late Miocene NE-SW trending (in the north) to N-S trending (in the south) fault bounded basin, filled by late Miocene to Recent volcanic rocks and continental sedimentary deposits (e.g.…”

Section: Study Areamentioning

confidence: 99%

“…Exposed volcanic products consist of basalts, rhyolites, ignimbrites and pyroclastic deposits. Monogenetic activity consists of spatter cones, scoria cones, maars and lava domes (Mazzarini et al, 1999;Abebe et al, 2005;Rooney et al, 2007;Corti, 2009;Rooney, 2010;Rooney et al, 2011).…”

Section: Study Areamentioning

confidence: 99%

See 1 more Smart Citation

Spatial relationship between earthquakes and volcanic vents in the central-northern Main Ethiopian Rift

Mazzarini

Keir

Isola

2013

Journal of Volcanology and Geothermal Research

Self Cite

View full text Add to dashboard Cite

During the breakup of continents extension is commonly accommodated by connected networks of fluid filled fractures (dykes) and by faults. Despite the importance of these two extension mechanisms their spatial relationship in three dimensions is poorly understood primarily because it is difficult to quantify the subsurface distribution of faulting and intrusion. In order to address this problem, we conduct a quantitative analysis of the spatial distribution and clustering of earthquakes and volcanic vents in the Main Ethiopian Rift in East Africa in order to understand how extension by faulting and intrusion is distributed throughout the volcanic rift. We use fractal analysis of earthquake epicentres in order to infer the 2D characteristics of the subsurface fault network, and directly test our model results against the 3D distribution of earthquake hypocentres. Our results show that fractal analysis of these features is a reliable means to characterise the 3D properties of the fault network. In addition, the strong similarity between the properties of the fault network derived from earthquakes and properties of the magma-filled fracture network derived from fractal analysis of volcanic vents strongly suggests that these are genetically linked. We then explore their spatial link using computation of earthquake and vent density, which shows that the zone of seismicity is generally around 20-30-km-wide, while the zone of vents is narrower and centred within the zone of seismicity. This spatial relationship suggests that the faults, which form rift axial grabens, are induced above a narrower and central zone of diking. We also demonstrate significant along-rift variation in degree of magmatism and faulting with regions of increased degree of diking inferred from a higher cone density characterised by reduced degree of faulting.

show abstract

“…However, both magmas originate from the same parental source of basalts formed from decompressional melting of the upper asthenosphere beneath the rift 22,23 . The basalts exhibit differences in major and trace elements, and radiogenic isotopes that vary more over the distances of adjacent scoria cones than between the axial and flank volcanic fields 24 .…”

mentioning

confidence: 99%

Off-rift volcanism in rift zones determined by crustal unloading

et al. 2014

Self Cite

View full text Add to dashboard Cite

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...

show abstract

Insights into extensional processes during magma assisted rifting: Evidence from aligned scoria cones

Cited by 88 publications

References 147 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

Spatial relationship between earthquakes and volcanic vents in the central-northern Main Ethiopian Rift

Off-rift volcanism in rift zones determined by crustal unloading

Contact Info

Product

Resources

About