Crust generated above the Iceland mantle plume: From continental rift to oceanic spreading center

Smallwood, John R.; Staples, Robert K.; Richardson, K. M.; White, R. S.

doi:10.1029/1999jb900176

Cited by 83 publications

(96 citation statements)

References 32 publications

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“…In contrast, a number of authors (e.g. Bott et al, 1971;Fleischer, 1971;Bott and Gunnarsson, 1985;Richardson et al;, Smallwood et al, 1999 proposed a crust of oceanic origin of this structure with a thickness between 20 and 35 km formed between 55 and 40 million years b.p. by volcanic activity in association to a hot spot.…”

Section: Introduction and Tectonic Settingmentioning

confidence: 98%

“…In the 1990, a large-scale seismic refraction experiment, the so-called FIRE line, was carried out extending from Iceland to the Faeroe Islands along the entire IFR and resulted in a velocity model down to 55 km depth (Richardson et al, 1998;Smallwood et al, 1999). Based on their seismic data, Richardson et al (1998) discuss two alternative models of which the first one would meet the velocity-depth distribution found along our line quite well.…”

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 99%

“…In a later study that combined the same seismic data set as well as MCS high-resolution data for the uppermost 1 km, Smallwood et al (1999) obtained a Moho depth of 27-28 km for the southeastern IFR. Again, the ridge in this part was interpreted to be of oceanic origin.…”

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 99%

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Crustal structure of the southeastern Iceland-Faeroe Ridge (IFR) from wide aperture seismic data

Bohnhoff¹,

Makris²

2004

Journal of Geodynamics

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The aseismic Iceland-Faeroe-Ridge (IFR) is of central importance in reconstructing the opening of the North Atlantic Ocean. To investigate the crustal structure of the IFR at its southeastern part we conducted a wide aperture seismic survey across the IFR from the Iceland Basin to the Norway Basin. Seismic energy was generated by two 60-litre sleeve guns and recorded by 42 ocean-bottom seismometers (OBS). Kinematic and dynamic forward modeling by two-point ray tracing was applied to develop a 2D velocity-depth model. The accuracy of the model obtained is better than 5% for both velocity and depth of interfaces. We find a Moho depth of 23 km below the crest of the ridge that decreases to about 15 km at either end of the line. The upper part of the crust exhibits P-wave velocities between 5.7 and 6.3 km/s that increase towards the Norway Basin. The lower crust is more homogeneous with v p ranging from 6.6 to 7.0 km/s. Upper and lower parts of the crust are separated by a first order discontinuity. Amplitudes (P m P) and arrival times (P n ) of wide-angle phases indicate upper-mantle velocities of 7.9 km/s. Furthermore we analyzed PS-converted phases for upper crustal depth levels and find a v p /v s ratio of 1.73 AE 0.04 equal to a Poisson's ratio of 0.25 with no significant lateral variations along the seismic line. On the crest of the ridge we identified a basalt layer embedded within the sedimentary sequence that was also penetrated by deep sea drilling and dated to 43AE 3.3 million years. Below the basalt layer we observed a low-velocity layer that is identified as Mesozoic sediment that was also observed to either end of the basalt. We conclude that the southeastern part of the IFR is composed of stretched continental crust and thus part of Paleo-Europe rather than oceanic crust formed by the Iceland hot spot. This conclusion is supported by the distribution of magnetic anomalies that allow identifying the passive continental margin approximately 100 km to the NW of our seismic line. #

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Section: Introduction and Tectonic Settingmentioning

confidence: 98%

Section: U N C O R R E C T E D P R O O Fmentioning

confidence: 99%

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Crustal structure of the southeastern Iceland-Faeroe Ridge (IFR) from wide aperture seismic data

Bohnhoff¹,

Makris²

2004

Journal of Geodynamics

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“…On the conjugate side, the main SDRs along SE Greenland become poorly defined towards the Greenland -Iceland Ridge. Both of these aseismic ridges are characterized by extremely thick igneous crust that is comparable to Iceland today (Smallwood et al 1999;Holbrook et al 2001). This suggests that welldeveloped SDRs form primarily along margin segments where the melt supply decreases as spreading becomes established, resulting in a rapid reduction in crustal thickness.…”

Section: Resultsmentioning

confidence: 96%

Regional distribution of volcanism within the North Atlantic Igneous Province

Horni

Hopper

Blischke

et al. 2017

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An overview of the distribution of volcanic facies units was compiled over the North Atlantic region. The new maps establish the pattern of volcanism associated with breakup and the initiation of seafloor spreading over the main part of the North Atlantic Igneous Province (NAIP). The maps include new analysis of the Faroe-Shetlands region that allows for a consistent volcanic facies map to be constructed over the entire eastern margin of the North Atlantic for the first time. A key result is that the various conjugate margin segments show a number of asymmetric patterns that are interpreted to result in part from pre-existing crustal and lithospheric structures. The compilation further shows that while the lateral extent of volcanism extends equally far to the south of the Iceland hot spot as it does to the north, the volume of material emplaced to the south is nearly double of that to the north. This suggests that a possible southward deflection of the Iceland mantle plume is a long-lived phenomenon originating during or shortly after impact of the plume.

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“…For example, oceanic crustal thickness was ∼8 km along the early AR (Breivik et al, 2006), as thick or thicker along much of the RR, and significantly thicker (>30 km) along the Iceland-Greenland and IcelandFaeroe volcanic ridges (e.g. Holbrook et al, 2001;Smallwood et al, 1999). Shortly after continental breakup, the relative location of the hotspot center was likely near the margin of east Greenland (Fig.…”

Section: Introductionmentioning

confidence: 99%

The origin of the asymmetry in the Iceland hotspot along the Mid-Atlantic Ridge from continental breakup to present-day

Howell

Ito

Breivik

et al. 2014

Earth and Planetary Science Letters

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The Iceland hotspot has profoundly influenced the creation of oceanic crust throughout the North Atlantic basin. Enigmatically, the geographic extent of the hotspot influence along the Mid-Atlantic Ridge has been asymmetric for most of the spreading history. This asymmetry is evident in crustal thickness along the present-day ridge system and anomalously shallow seafloor of ages ∼49-25 Ma created at the Reykjanes Ridge (RR), SSW of the hotspot center, compared to deeper seafloor created by the nowextinct Aegir Ridge (AR) the same distance NE of the hotspot center. The cause of this asymmetry is explored with 3-D numerical models that simulate a mantle plume interacting with the ridge system using realistic ridge geometries and spreading rates that evolve from continental breakup to present-day. The models predict plume-influence to be symmetric at continental breakup, then to rapidly contract along the ridges, resulting in widely influenced margins next to uninfluenced oceanic crust. After this initial stage, varying degrees of asymmetry along the mature ridge segments are predicted. Models in which the lithosphere is created by the stiffening of the mantle due to the extraction of water near the base of the melting zone predict a moderate amount of asymmetry; the plume expands NE along the AR ∼70-80% as far as it expands SSW along the RR. Without dehydration stiffening, the lithosphere corresponds to the near-surface, cool, thermal boundary layer; in these cases, the plume is predicted to be even more asymmetric, expanding only 40-50% as far along the AR as it does along the RR. Estimates of asymmetry and seismically measured crustal thicknesses are best explained by model predictions of an Iceland plume volume flux of ∼100-200 m 3 /s, and a lithosphere controlled by a rheology in which dehydration stiffens the mantle, but to a lesser degree than simulated here. The asymmetry of influence along the present-day ridge system is predicted to be a transient configuration in which plume influence along the Reykjanes Ridge is steady, but is still widening along the Kolbeinsey Ridge, as it has been since this ridge formed at ∼25 Ma.

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Crust generated above the Iceland mantle plume: From continental rift to oceanic spreading center

Cited by 83 publications

References 32 publications

Crustal structure of the southeastern Iceland-Faeroe Ridge (IFR) from wide aperture seismic data

Crustal structure of the southeastern Iceland-Faeroe Ridge (IFR) from wide aperture seismic data

Regional distribution of volcanism within the North Atlantic Igneous Province

The origin of the asymmetry in the Iceland hotspot along the Mid-Atlantic Ridge from continental breakup to present-day

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