Hyperextension, serpentinization, and weakening: A new paradigm for rifted margin compressional deformation

Lundin, Erik; Doré, A. G.

doi:10.1130/g31499.1

Cited by 158 publications

(126 citation statements)

References 26 publications

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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%

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%

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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“…Reston and Perez-Gussinye, 2007;Franke, 2013); the role of depth dependent stretching and multiple rift stages (e.g. Huismans & Beaumont, 2011;Soares et al, 2012); and the influence of mantle plumes (White and McKenzie, 1989;Clift and Turner, 1995;Corti, 2009;Lundin and Doré, 2011). These studies commonly focus on portions of margins, or their equivalents on the conjugate margins.…”

Section: Introductionmentioning

confidence: 99%

Tectonic variation and structural evolution of the West Greenland continental margin

Alsulami¹,

Paton²,

Cornwell³

2015

Bulletin

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“…Müntener and Manatschal 2006) and hyperextension is not exclusive to magma-poor margins such as Iberia. For example the northeast Atlantic 'volcanic' margin was affected by hyperextension processes in the Late Jurassic -Early Cretaceous (Osmundsen and Ebbing 2008;Lundin and Doré 2011).…”

Section: Introductionmentioning

confidence: 99%

The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean

Chew

Staal

2014

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A combination of deep seismic imaging and drilling has demonstrated that the ocean-continent transition (OCT) of present-day, magma-poor, rifted continental margins is a zone of hyperextension characterized by extreme thinning of the continental crust that exhumed the lowermost crust and/or serpentinized continental mantle onto the seafloor. The OCT on present-day margins is difficult to sample, and so much of our knowledge on the detailed nature of OCT sequences comes from obducted, magma-poor OCT ophiolites such as those preserved in the upper portions of the Alpine fold-and-thrust belt. Allochthonous, lens-shaped bodies of ultramafic rock are common in many other ancient orogenic belts, such as the Caledonian – Appalachian orogen, yet their origin and tectonic significance remains uncertain. We summarize the occurrences of potential ancient OCTs within this orogen, commencing with Laurentian margin sequences where an OCT has previously been inferred (the Dalradian Supergroup of Scotland and Ireland and the Birchy Complex of Newfoundland). We then speculate on the origin of isolated occurrences of Alpine-type peridotite within Laurentian margin sequences in Quebec – Vermont and Virginia – North Carolina, focusing on rift-related units of Late Neoproterozoic age (so as to eliminate a Taconic ophiolite origin). A combination of poor exposure and pervasive Taconic deformation means that origin and emplacement of many ultramafic bodies in the Appalachians will remain uncertain. Nevertheless, the common occurrence of OCT-like rocks along the whole length of the Appalachian – Caledonian margin of Laurentia suggests that the opening of the Iapetus Ocean may have been accompanied by hyperextension and the formation of magma-poor margins along many segments.SOMMAIREDes travaux d’imagerie sismique et des forages profonds ont montré que la transition océan-continent (OCT) de marges continentales de divergence pauvre en magma exposée de nos jours, correspond à une zone d’hyper-étirement tectonique caractérisée par un amincissement extrême de la croûte continentale, qui a exhumé sur le fond marin, jusqu’à la tranche la plus profonde de la croûte continentale, voire du manteau continental serpentinisé. Parce qu’on peut difficilement échantillonner l’OCT sur les marges actuelles, une grande partie de notre compréhension des détails de la nature de l’OCT provient d’ophiolites pauvres en magma d’une OCT obduite, comme celles préservées dans les portions supérieures de la bande plissée alpine. Des masses lenticulaires de roches ultramafiques allochtones sont communes dans de nombreuses autres bandes orogéniques anciennes, comme l’orogène Calédonienne-Appalaches, mais leur origine et signification tectonique reste incertaine. Nous présentons un sommaire des occurrences d’OCT potentielles anciennes de cet orogène, en commençant par des séquences de la marge laurentienne, où la présence d’OCT a déjà été déduites (le Supergroupe Dalradien d’Écosse et d'Irlande, et le complexe de Birchy de Terre-Neuve). Nous spéculons ensuite sur l'origine de cas isolés de péridotite de type alpin dans des séquences de marge des Laurentides du Québec-Vermont et de la Virginie-Caroline du Nord, en nous concentrant sur les unités de rift d'âge néoprotérozoïque tardif (pour éviter les ophiolites du Taconique). La conjonction d’affleurements de piètre qualité et de la déformation taconique omniprésente, signifie que l'origine et la mise en place de nombreuses masses ultramafiques dans les Appalaches demeureront incertaines. Néanmoins, la présence fréquente de roches de type OCT tout le long de la marge Calédonnienne-Appalaches de Laurentia suggère que l'ouverture de l'océan Iapetus peut avoir été accompagnée d’hyper-étirement et de la formation de marges pauvres en magma le long de nombreux segments.

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Hyperextension, serpentinization, and weakening: A new paradigm for rifted margin compressional deformation

Cited by 158 publications

References 26 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

Tectonic variation and structural evolution of the West Greenland continental margin

The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean

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