Tomographic image of the Mid‐Atlantic Plate Boundary in southwestern Iceland

Bjarnason, Ingi Þorleifur; Menke, William; Flóvenz, Ólafur G.; Caress, David W.

doi:10.1029/92jb02412

Cited by 174 publications

(180 citation statements)

References 33 publications

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“…This value falls at the lower end of the measurements on Iceland (e.g. Bjarnason et al, 1993), and may be interpreted as gabbros derived from high temperature melt, thus increasing the Mg content, subject to normal present-day temperatures. Such lower temperatures would be expected for this profile, being primarily located to the east of the main ridge crest.…”

Section: Icelandic Type Oceanic Crustmentioning

confidence: 78%

“…The segment between the COB and the Mohns Ridge oceanic crust is interpreted as an Icelandic type oceanic plateau (anomalously thick oceanic crust), based on the similarities with Iceland in crustal layering and P-wave velocities (Bjarnason et al, 1993;Allen et al, 2002;Gudmundsson, 2003;Sigmundsson, 2006). Sampling of 32e24 Ma lavas, gabbros and volcano-clastic sediments along the southern slope of the West Jan Mayen Fracture Zone (WJMFZ) has confirmed that the northernmost Jan Mayen Ridge formed within an area of Oligocene magmatism (Pedersen et al, 2010).…”

Section: The P-wave Modelsmentioning

confidence: 99%

“…Controlled source experiments on Iceland have revealed Vp/Vsratios in oceanic layer 3 in the range 1.75e1.80 (Bjarnason et al, 1993;Brandsdottir et al, 1997;Staples et al, 1997;Darbyshire et al, 1998;Menke et al, 1998). These values are consistent with gabbro well below the solidus (Kampfmann and Berckhemer, 1985).…”

Section: Icelandic Type Oceanic Crustmentioning

confidence: 99%

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Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

et al. 2015

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a b s t r a c tIn order to gain insight into the lithology and crustal evolution of the northern Jan Mayen Ridge, North Atlantic, the horizontal components of an Ocean Bottom Seismometer (OBS) dataset were analyzed with regard to Vp/Vs-modeling and seismic anisotropy. The modeling suggests that the northernmost part of the ridge consists of Icelandic type oceanic crust, bordered to the north by anomalously thick oceanic crust formed at the Mohns spreading ridge. The modeled Vp/Vs-ratios suggest variations in gabbroic composition and present-day temperatures in the area. Anisotropy analysis reveals a fast S-wave component along the Jan Mayen Ridge. This pattern of anisotropy is most readily interpreted as dikes intruded along the ridge, suggesting that the magmatism can be related to the development of a leaky transform since Early Oligocene.

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Section: Icelandic Type Oceanic Crustmentioning

confidence: 78%

Section: The P-wave Modelsmentioning

confidence: 99%

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Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

et al. 2015

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“…The report in the 1990s was thus a re-discovery [Bjarnason et al, 1993;Björnsson et al, 2005]. Nevertheless, it resulted in the material previously interpreted as hot, partially molten mantle being reinterpreted as sub-solidus, gabbroic, lower crust.…”

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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“…The match of the model predicted times to these additional phases reinforces our crustal thickness interpretation in this region. Bjarnason et al [1993] identified the Moho beneath the HV shot point at 21 kin, constraining its depth from both Prop and mantle turning rays. We fixed the Moho at this depth beneath HV, interpolating the boundary from where it is constrained by the RISE data.…”

Section: Line A: Reykjanes Peninsulamentioning

confidence: 99%

Crustal structure of the northern Reykjanes Ridge and Reykjanes Peninsula, southwest Iceland

Weir¹,

White²,

Brandsdóttír³

et al. 2001

J. Geophys. Res.

133

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Abstract. Results from the Reykjanes-Iceland Seismic Experiment (RISE)show that the thickness of zero-age crust decreases from 21 km in southwest Iceland to 11 km at 62ø40•N on the Reykjanes Ridge. This implies a decrease in mantle potential temperature of •-130 øC, with increasing distance from the center of the Iceland mantle plume, along this 250 km transect of the plate boundary. The crust thins off-axis at 63øN, from 12.7 km thick at 0 Ma to 9.8 km at 5 Ma, most likely due to a •40øC change in asthenospheric mantle temperature between these times. This provides evidence for the passage of a pulse of hotter asthenospheric mantle material beneath the present spreading center. A reflective body, the top of which lies at 9-11 km depth, is identified in the lower crust just west of the tip of the Reykjanes Peninsula. Synthetic seisrnogram modeling of the wide-angle reflections from this body suggests that it corresponds to a zone of high-velocity (>_7.5 krn s -x), high-magnesium rocks in the lower crust. The P to S wave velocity ratio beneath the peninsula is 1.78, implying that crustal temperatures are below the solidus. Gravity modeling shows the RISE models to be consistent with the observed gravity field. Mantle densities are lower beneath the ridge axis than beneath older crust, consistent with lithospheric cooling with age. Iceland and the Reykjanes RidgeIceland has been created where the slow spreading Mid-Atlantic Ridge passes directly over a mantle plume.McKenzie and Bickle [1988] showed that for decompression melting of the mantle at oceanic spreading centers the melt volume produced relies sensitively on the mantle temperature. Thus, assuming passive upwelling, the presence of the spreading center allows us to estimate the mantle temperature at a range of distances from the plume by measuring the igneous crustal thickness.•

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Tomographic image of the Mid‐Atlantic Plate Boundary in southwestern Iceland

Cited by 174 publications

References 33 publications

Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

Are ‘hot spots’ hot spots?

Crustal structure of the northern Reykjanes Ridge and Reykjanes Peninsula, southwest Iceland

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