The lithosphere below the Rockall Trough: wide-angle seismic evidence for extensive serpentinisation

O’Reilly, B. M.; Hauser, F.; Jacob, A. W. B.; Shannon, P. M.

doi:10.1016/0040-1951(95)00149-2

Cited by 99 publications

(86 citation statements)

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“…Mostly, the high velocity seismic layer is found below the surrounding basins with oceanic or thinned continental crust. In these regions, the high velocity layer is also hypothesized to be either serpentinized mantle or mafic underplating (O'Reilly et al, 1996;Reston et al, 2001;Lundin and Doré, 2011).…”

Section: Continental Fragments and Microcontinents: Crustal Structurementioning

confidence: 99%

“…The high velocity layer under the Faroe Bank is interpreted to be a layer of mafic sill intrusions in the crust related to the Iceland plume or convective upwellings (Harland et al, 2009). Under the Rockall Bank, this layer is believed to be serpentinized upper mantle (O'Reilly et al, 1996). For the continental fragments off the Australian margin, the high velocity lower layer is interpreted as mafic underplating (Grobys et al, 2009).…”

Section: Continental Fragments and Microcontinents: Crustal Structurementioning

confidence: 99%

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Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Tetreault

Buiter

2014

Solid Earth

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Abstract. Allochthonous accreted terranes are exotic geologic units that originated from anomalous crustal regions on a subducting oceanic plate and were transferred to the overriding plate by accretionary processes during subduction. The geographical regions that eventually become accreted allochthonous terranes include island arcs, oceanic plateaus, submarine ridges, seamounts, continental fragments, and microcontinents. These future allochthonous terranes (FATs) contribute to continental crustal growth, subduction dynamics, and crustal recycling in the mantle. We present a review of modern FATs and their accreted counterparts based on available geological, seismic, and gravity studies and discuss their crustal structure, geological origin, and bulk crustal density. Island arcs have an average crustal thickness of 26 km, average bulk crustal density of 2.79 g cm −3 , and three distinct crustal units overlying a crust-mantle transition zone. Oceanic plateaus and submarine ridges have an average crustal thickness of 21 km and average bulk crustal density of 2.84 g cm −3 . Continental fragments presently on the ocean floor have an average crustal thickness of 25 km and bulk crustal density of 2.81 g cm −3 . Accreted allochthonous terranes can be compared to these crustal compilations to better understand which units of crust are accreted or subducted. In general, most accreted terranes are thin crustal units sheared off of FATs and added onto the accretionary prism, with thicknesses on the order of hundreds of meters to a few kilometers. However, many island arcs, oceanic plateaus, and submarine ridges were sheared off in the subduction interface and underplated onto the overlying continent. Other times we find evidence of terrane-continent collision leaving behind accreted terranes 25-40 km thick. We posit that rheologically weak crustal layers or shear zones that were formed when the FATs were produced can be activated as detachments during subduction, allowing parts of the FAT crust to accrete and others to subduct. In many modern FATs on the ocean floor, a sub-crustal layer of high seismic velocities, interpreted as ultramafic material, could serve as a detachment or delaminate during subduction.

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Section: Continental Fragments and Microcontinents: Crustal Structurementioning

confidence: 99%

Section: Continental Fragments and Microcontinents: Crustal Structurementioning

confidence: 99%

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Tetreault

Buiter

2014

Solid Earth

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“…If depleted continental lithospheric mantle underlies the basin, its density may be lower than that of the mantle beneath the oceanic regions to the north and south, although the effect is more marked for Archaean lithosphere than for the Proterozoic lithosphere that is probable in this area (Poudjom Djomani et al 2001). The density of the upper mantle could have been reduced by partial serpentinisation if extreme extension allowed the ingress of seawater to upper mantle levels, as has been suggested in the case of the Rockall Basin to the west of Ireland (O'Reilly et al 1996). Relatively low temperatures are, however, required for the lower crust to deform in a brittle fashion and for a sufficient thickness of the upper mantle to lie within the stability field for serpentinite (Pérez-Gussinyé et al 2001).…”

Section: Discussionmentioning

confidence: 95%

The three-dimensional lithospheric structure of the Falkland Plateau region based on gravity modelling

Kimbell

Richards

2008

JGS

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Abstract:The lithospheric structure of the Falkland Plateau region has been modelled by making an initial estimate on the basis of local isostasy and then refining the geometries by inversion of gravity anomalies. The model predicts a crustal thickness beneath the Falkland Plateau Basin that is more than twice that previously inferred from seismic evidence. The preferred explanation is that the seismic survey detected high-velocity (?underplated) lower crust rather than upper mantle. This is compatible with the results of deep seismic experiments over the conjugate Filchner Block of Antarctica and also appears likely on the basis of the position of the Falkland Plateau Basin in relation to the Karoo-Ferrar magmatic province at the time of extension. Continental crust is inferred to be continuous beneath the northern part of the Falkland Plateau, as there are consistent magnetic and flexural anomalies associated with the continent-ocean boundary. Flexural modelling of the southern margin of the plateau indicates lateral variations in strength, with the strongest lithosphere beneath the Falkland Plateau Basin. This may indicate thick oceanic crust beneath the southern part of the basin or the effect of thinning relatively weak continental crust and replacing it with relatively strong underplating. [End of Abstract]

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“…Zonenshain & Le Pichon 1986) and as layered intrusions within rifts and in highly extended basins (in both volcanic and non-volcanic continental margins), where the continental crust is highly stretched (e.g. O'Reilly et al 1996).…”

Section: Nigel Smithmentioning

confidence: 99%

Hydrogen exploration: a review of global hydrogen accumulations and implications for prospective areas in NW Europe

Smith

Shepherd

Styles

et al. 2005

PGC

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From a geological perspective, hydrogen has been neglected. It is not as common as biogenic or thermogenic methane, which are ubiquitous in hydrocarbon basins, or carbon dioxide, which is common in geologically-active areas of the world. Nevertheless, small flows of hydrogen naturally reach the Earth's surface, occur in some metal mines and emerge beneath the oceans in a number of places worldwide. These occurrences of hydrogen are associated with abiogenic and biogenic methane, Further research should aim to identify the extent of the hydrogen flux and its probable dominant role in the abiogenic production of hydrocarbons in Precambrian times, a natural process now largely replaced by biogenic participation. A similar industrial process replicates serpentinization, producing hydrogen and ultimately liquid hydrocarbons on a commercial scale in some countries. It remains to be proved whether a contribution from exploration can be made to any future Hydrogen Economy.

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The lithosphere below the Rockall Trough: wide-angle seismic evidence for extensive serpentinisation

Cited by 99 publications

References 50 publications

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

Future accreted terranes: a compilation of island arcs, oceanic plateaus, submarine ridges, seamounts, and continental fragments

The three-dimensional lithospheric structure of the Falkland Plateau region based on gravity modelling

Hydrogen exploration: a review of global hydrogen accumulations and implications for prospective areas in NW Europe

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