Melt generation at volcanic continental margins: No need for a mantle plume?

Wijk, Jolante van; Huismans, Ritske S.; Voorde, M. ter; Cloetingh, S.A.P.L.

doi:10.1029/2000gl012848

Cited by 110 publications

(62 citation statements)

References 26 publications

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“…Due to crustal thinning mantle material rises and consequently decompressional melting processes in the head of the rising material cause significant volumes of melt (van Wijk et al, 2001). In these models the volume of melt is controlled by the thinning factor beta.…”

Section: Crustal Structure At Springbok and Along The Marginmentioning

confidence: 99%

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

2009

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The passive margin of the South Atlantic shows typical features of a rifted volcanic continental margin, encompassing seaward dipping reflectors, continental flood basalts and high-velocity/density lower crust at the continentocean transition, probably emplaced during initial seafloor spreading in the Early Cretaceous.The Springbok profile offshore western South Africa is a combined transect of reflection and refraction seismic data. This paper addresses the analysis of the seismic velocity structure in combination with gravity modelling and isostatic modelling to unravel the crustal structure of the passive continental margin from different perspectives.The velocity modelling revealed a segmentation of the margin into three distinct parts of continental, transitional and oceanic crust. As observed at many volcanic margins, the lower crust is characterised by a zone of high velocities with up to 7.4 km/s. The conjunction with gravity modelling affirms the existence of this body and at the same time substantiated its high densities, found to be 3100 kg/m³. Both approaches identified the body to have a thickness of about 10 km. Yet, the gravity modelling predicted the transition between the highdensity body towards less dense material farther west than initially anticipated from velocity modelling and confirmed this density gradient to be a prerequisite to reproduce the observed gravity signal. 2Finally, isostatic modelling was applied to predict average crustal densities if the margin was isostatically balanced. The results imply isostatic equilibrium over large parts of the profile, smaller deviations are supposed to be compensated regionally. The calculated load distribution along the profile implies that all pressures are hydrostatic beneath a depth of 45 km.3

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Section: Crustal Structure At Springbok and Along The Marginmentioning

confidence: 99%

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

2009

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“…The majority of successfully rifted margins show evidence for magmatism prior to plate rupture (e.g., Coffi n and Eldholm, 1994; Menzies et al, 2002;White et al, 2008;Bronner et al, 2011). Yet, thermo-mechanical models of evolution in heterogeneous continental lithosphere are largely 2D (e.g., Keen, 1985;Dunbar and Sawyer, 1989;Lavier and Manatschal, 2006;Schmeling, 2010;Huismans and Beaumont, 2011), and only a few address the effects of melting in rifting processes (e.g., van Wijk et al, 2001;Bialas et al, 2010;Schmeling and Wallner, 2012).…”

Section: A B Cmentioning

confidence: 99%

“…Replacement of mantle lithosphere by hotter asthenosphere transfers heat to the lithosphere beneath the stretched zone, reducing rock density, leading to a regional, time-dependent uplift over time scales of tens of millions of years (e.g., Şengör and Burke, 1978;Keen, 1985). The passive mantle upwelling may be enhanced by anomalously hot mantle upwellings or plumes and/or small-scale convection induced by the steep gradients at the transition between thinned and unthinned lithosphere (e.g., Buck, 1986;King and Anderson, spe 500-11 1st pgs page 4 1998;van Wijk et al, 2001van Wijk et al, , 2008 (Fig. 1A).…”

Section: Review Of Rifting Processesmentioning

confidence: 99%

The time scales of continental rifting: Implications for global processes

Ebinger

Wijk

Keir

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

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The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound, multiple episodes of which combine to produce the observed, time-averaged rift zone architecture. The aim of our synthesis of current research initiatives into continental rifting-to-rupture processes is to quantify the time and length scales of faulting and magmatism that produce the time-averaged rift structures imaged in failed rifts and passive margins worldwide. We compare and contrast seismic and geodetic strain patterns during discrete, intense rifting episodes in magmatic and amagmatic sectors of the East African rift zone that span early-to late-stage rifting. We also examine the longer term rifting cycle and its relation to changing far-fi eld extension directions with examples from the Rio Grande rift zone and other cratonic rifts. Over time periods of millions of years, periods of rotating regional stress fi elds are marked by a lull in magmatic activity and a temporary halt to tectonic rift opening. Admittedly, rifting cycle comparisons are biased by the short time scale of global seismic and geodetic measurements, which span a small fraction of the 10 2 -10 5 year rifting cycle. Within rift sectors with upper crustal magma chambers beneath the central rift valley (e.g., Main Ethiopian, Afar, and Eastern or Gregory rifts) seismic energy release accounts for a small fraction of the deformation; most of the strain is accommodated by magma intrusion and slowslip. Magma intrusion processes appear to decrease the time period between rifting episodes, effectively accelerating the rift to rupture process. Thus, the inter-seismic period in rift zones with crustal magma reservoirs is strongly dependent upon the

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“…These formed when the Eurasian continent broke up at ~ 54 Ma, splitting continental lithosphere up to 200 km thick, and allowing material to rise from those great depths [van Wijk et al, 2004;van Wijk et al, 2001]. …”

Section: The North Atlantic Igneous Provincementioning

confidence: 99%

Are ‘hot spots’ hot spots?

Foulger

2012

Journal of Geodynamics

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe term 'hot spot' emerged in the 1960's from speculations that Hawaii might have its origins in an unusually hot source region in the mantle. It subsequently become widely used to refer to volcanic regions considered to be anomalous in the then-new plate tectonic paradigm. It carried with it the implication that volcanism a) is emplaced by a single, spatially restricted, mongenetic melt-delivery system, assumed to be a mantle plume, and b) that the source is unusually hot. This model has tended to be assumed a priori to be correct. Nevertheless, there are many geological ways of testing it, and a great deal of work has recently been done to do so. Two fundamental problems challenge this work. First is the difficulty of deciding a 'normal' mantle temperature against which to compare estimates. This is usually taken to be the source temperature of midocean ridge basalts (MORB). However, Earth's surface conduction layer is ~ 200 km thick, and such a norm is not appropriate if the lavas under investigation formed deeper than the 40-50 km source depth of MORB. Second, methods for estimating temperature suffer from ambiguity of interpretation with composition and partial melt, controversy regarding how they should be applied, lack of repeatability between studies using the same data, and insufficient precision to detect the 200-300˚C temperature variations postulated. Available methods include multiple seismological and petrological approaches, modelling bathymetry and topography, and measuring heat flow. Investigations have been carried out in many areas postulated to represent either (hot) plume heads or (hotter) tails. These include sections of the mid-ocean spreading ridge postulated to include ridge-centred plumes, the North Atlantic Igneous Province, Iceland, Hawaii, oceanic plateaus, and high-standing continental areas such as the Hoggar swell. Most volcanic regions that may reasonably be considered anomalous in the simple plate-tectonic paradigm have been built by volcanism distributed throughout hundreds, even thousand of kilometres, and as yet no unequivocal evidence has been produced that any of them have high temperature anomalies compared with average mantle temperature for the same (usually unknown) depth elsewhere. Critical investigation of the genesis processes of 'anomalous' volcanic regions would be encouraged if use of the term 'hot spot' were discontinued in favor of one that does not assume a postulated origin, but is a description of unequivocal, observed char...

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Melt generation at volcanic continental margins: No need for a mantle plume?

Cited by 110 publications

References 26 publications

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

Deep structure of the western South African passive margin — Results of a combined approach of seismic, gravity and isostatic investigations

The time scales of continental rifting: Implications for global processes

Are ‘hot spots’ hot spots?

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