Evidence for tectonic emplacement of ultramafic and associated rocks in the pre-Silurian eugeoclinal belt of western New England; vestiges of an ancient accretionary wedge

Stanley, Rolfe S.; Roy, Dana L.; Hatch, Norman L.; Knapp, Douglas Alan

doi:10.2475/ajs.284.4-5.559

Cited by 29 publications

(15 citation statements)

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“…2) is a steeply east-dipping downto-the-east normal fault of presumed Silurian age that reactivated an earlier thrust surface (Kim et al, 1999); detailed microstructural analysis has verified the normal-fault interpretation (Lamon and Doolan, 2001). The name ''Burgess Branch fault zone'' has supplanted the name ''Belvidere Mountain Fault zone'' of Stanley et al (1984) (Kim et al, 1999). The Belvidere Mountain Fault zone was specifically redefined to represent only the sole thrust at the base of the Belvidere Mountain Complex (Kim et al, 1999).…”

Section: Local Geologic Settingmentioning

confidence: 97%

Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

Kim

Coish

Evans

et al. 2003

Geo. Society Am. Bull.

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Metadiabasic intrusions of the Mount Norris Intrusive Suite occur in faultbounded lithotectonic packages containing Stowe, Moretown, and Cram Hill Formation lithologies in the northern VermontRowe-Hawley belt, a proposed Ordovician arc-trench gap above an east-dipping subduction zone. Rocks of the Mount Norris Intrusive Suite are characteristically massive and weakly foliated, have chilled margins, contain xenoliths, and have sharp contacts that both crosscut and are parallel to early structural fabrics in the host metasedimentary rocks. Although the mineral assemblage of the Mount Norris Intrusive Suite is albite ؉ actinolite ؉ epidote ؉ chlorite ؉ calcite ؉ quartz, intergrowths of albite ؉ actinolite are probably pseudomorphs after plagioclase ؉ clinopyroxene. The metadiabases are subalkaline, tholeiitic, hypabyssal basalts with preserved ophitic texture. A backarcbasin tectonic setting for the intrusive suite is suggested by its LREE (light rare earth element) enrichment, negative NbTa anomalies, and Ta/Yb vs. Th/Yb trends. Although no direct isotopic age data are available, the intrusions are broadly Ordovician because their contacts are clearly folded by the earliest Acadian (Silurian-Devonian) folds. Field evidence and geochemical data suggest compelling along-strike correlations with the Coburn † Hill Volcanics of northern Vermont and the Bolton Igneous Group of southern Quebec. Isotopic and stratigraphic age constraints for the Bolton Igneous Group bracket these backarc magmas to the 477-458 Ma interval. A tectonic model that begins with east-dipping subduction and progresses to outboard west-dipping subduction after a syncollisional polarity reversal best explains the intrusion of deformed metamorphosed metasedimentary rocks by backarc magmas.

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Section: Local Geologic Settingmentioning

confidence: 97%

Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

Kim

Coish

Evans

et al. 2003

Geo. Society Am. Bull.

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“…Plagiogranite in the Thetford ophiolite has been dated at 479 Ma (Dunning et al 1986;Dunning & Pedersen 1988) and in Orford at 504 Ma (David & Marquis 1994), generally consistent with a wide geographic range of ophiolite localities in Newfoundland, Ireland, Scotland and Norway in the range 495-480 Ma (Pedersen & Furnes 1997). In the upper part of the Thetford ophiolite there is a transition in basalt volcanic chemistry from MORB-like to tholeiitic arc-like to boninitic (Laurent 1977;Laurent et al 1979;Tremblay 1992;Hébert & Bédard 1998), suggesting ophiolite genesis in the setting of a rifted immature intra-oceanic arc, a process that may have led to subsequent hot emplacement of the ophiolite onto the continental margin (St-Julien & Hubert 1979;Stanley et al 1984), as well as early high-P, low-T metamorphism (Laird & Albee 1981a, 1981bLaird et al 1984), as worked out in detail in the case of Oman (Coleman 1981;Ghent & Stout 1981;Lanphere 1981;Saddiqi et al 1995). It is puzzling that thrust emplacement of ophiolite onto the supposed outer continental margin seems to have had no noticeable effect on deposition in the co-eval carbonate bank and shelf.…”

Section: Ophiolite Emplacement and Its Settingmentioning

confidence: 97%

Paleozoic orogens in New England, USA

Robinson

Tucker²,

Bradley

et al. 1998

GFF

156

131

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“…These rocks (the Vermont -Quebec serpentine belt of Doolan et al 1982) have been considered to represent remnants of tectonically emplaced slivers of Taconic Penrose-type ophiolites (Stanley et al 1984), although nowhere do they constitute a typical Penrose-type ophiolite stratigraphy.…”

Section: Quebec -Vermontmentioning

confidence: 99%

“…The Vermont Appalachians lack well-developed ophiolite sequences but slivers of highly serpentinized peridotite occur in the Green Mountain, Rowe, Moretown, and Hawley slices (Fig. 8) and have been interpreted as Penrose-type ophiolitic remnants (Doolan et al 1982;Stanley et al 1984).…”

mentioning

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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Evidence for tectonic emplacement of ultramafic and associated rocks in the pre-Silurian eugeoclinal belt of western New England; vestiges of an ancient accretionary wedge

Cited by 29 publications

References 0 publications

Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

Supra–subduction zone extensional magmatism in Vermont and adjacent Quebec: Implications for early Paleozoic Appalachian tectonics

Paleozoic orogens in New England, USA

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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