Regional Tectonic Synthesis of Northwestern New England and Adjacent Quebec

Cady, Wallace M.

doi:10.1130/mem120-p1

Cited by 18 publications

(26 citation statements)

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“…In the southern part of the area, the fold r axes trend almost north-south but in the northern parts they are N40°E and in between they describe an arc, convex to the northwest. This arc is the Sutton Mountains salient (Rankin 1976), which has also been called the New England salient (Cady 1969). The trends of the various tectonic lithofacies units (Williams 1978) and -the geophysical anomalies describe the same general curvature.…”

Section: Geological Settingmentioning

confidence: 97%

Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus

Kumarapeli¹,

Goodacre²

1981

Can. J. Earth Sci.

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Prominent, nearly coincident, positive gravity and magnetic anomalies occur in the Sutton Mountains region, centered about 100 km east of Montreal, Quebec. Several lines of evidence indicate that the gravity anomaly stems from two principal sources: a deep (mid and lower crustal) source of speculative origin and a shallow source identifiable with a narrow belt of late Precambrian -early Cambrian metavolcanic rocks, the Tibbit Hill volcanics. The magnetic anomaly seems to be produced mainly by the metavolcanic rocks. Three-dimensional modelling of a residual gravity anomaly, supplemented by two-dimensional modelling of the magnetic anomaly, shows that the seemingly minor belt of metavolcanic rocks constitutes the surface expression of a thick (maximum thickness -8 km) pile of dominantly mafic volcanics, which are only slightly exposed at the present level of erosion.The Tibbit Hill volcanics are regarded as products of rift-related volcanism that occurred at an rrr triple junction developed during the early stages of the opening of the Iapetus Ocean. The Ottawa graben is probably the failed of this triple junction. The emplacement of the Grenville dike swarm whose trend is nearly coincident with that of the Ottawa graben was probably coeval with the volcanism in the Sutton Mountains region. The present work shows that the volcanism in the region was on a much larger scale than hitherto recognized.On observe des anomalies prokminentes, presque coincidentes, de gravitC positive et de magnCtisme dans la rtgion des monts Sutton, dont le centre se situe a environ 100km a l'est de MontrCal au QuCbec. Plusieurs lignes d'kvidence indiquent que I'anomalie de gravitC provient de deux sources principales; une source profonde (partie mtdiane ou profonde de la create) d'origine incertaine et une source peu profonde qu'on identifie a une zone Ctroite de roches mCtavolcaniques, les volcaniques de Tibbit Hill, datant de la fin du PrCcambrien au debut du Cambrien. L'anomalie magnetique semble provenir surtout des roches mCtavolcaniques. Un modkle en trois dimensions d'une anomalie de gravitC rtsiduelle, complCtt par un modkle en deux dimensions de I'anomalie magnetique, montre que la zone apparemment nCgligeable des roches mCtavolcaniques constitue I'expression en surface d'un empilement Cpais (maximum de 8 km environ) de roches volcaniques surtout mafiques qui n'est que trks legkrement expos6 au niveau actuel d'trosion.

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Section: Geological Settingmentioning

confidence: 97%

Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus

Kumarapeli¹,

Goodacre²

1981

Can. J. Earth Sci.

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“…Ordovician-Silurian relations in northern Maine are analogous to those on New World Island. Polymictic conglomerates overlap northward on the earlier Paleozoic rocks of the Boundary Mountain anticlinorium (Cady, 1969;Green and Guidotti, 1968;Hall, 1969;Moench, 1970Moench, , 1973Pavlides and others, 1968). But if one becomes complacent, he may overlook the presence of the Silurian sequence with volcanic rocks at Sops Arm, within the Cabot fault zone on White Bay, far to the west (Lock, 1969)!…”

Section: Environment Of the Dunnagementioning

confidence: 97%

Dunnage Melange and Subduction of the Protacadic Ocean Northeast Newfoundland

Kay

1976

175 : Dunnage Melange and Subduction of the Protacadic Ocean Northeast Newfoundland

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“…The average amphibolite we use is an average of 20 bulk rock analyses of greenstones and amphibolites from Vermont, which occur as dykes or volcanics of dominantly tholeiitic affinity (bulk composition A (Laird; 1980); Table 2). This bulk composition is intermediate to those presented by Cady (1969), Cooper & Lovering (1970), Helms et al . (1987) and Yardley (1989), and thus provides an appropriate composition to address the role of bulk composition and P–T in the development of mineral assemblages in amphibolites.…”

Section: Introductionmentioning

confidence: 99%

Amphibolites with staurolite and other aluminous minerals: calculated mineral equilibria in NCFMASH

Arnold¹,

Powell²,

Sandiford³

2000

Journal Metamorphic Geology

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Amphibolite facies mafic rocks that consist mainly of hornblende, plagioclase and quartz may also contain combinations of chlorite, garnet, epidote, and, more unusually, staurolite, kyanite, sillimanite, cordierite and orthoamphiboles. Such assemblages can provide tighter constraints on the pressure and temperature evolution of metamorphic terranes than is usually possible from metabasites. Because of the high variance of most of the assemblages, the phase relationships in amphibolites depend on rock composition, in addition to pressure, temperature and fluid composition. The mineral equilibria in the Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O (NCFMASH) model system demonstrate that aluminium content is critical in controlling the occurrence of assemblages involving hornblende with aluminous minerals such as sillimanite, kyanite, staurolite and cordierite. Except in aluminous compositions, these assemblages are restricted to higher pressures. The iron to magnesium ratio (XFe), and to a lesser extent, sodium to calcium ratio, have important roles in determining which (if any) of the aluminous minerals occur under particular pressure–temperature conditions. Where aluminous minerals occur in amphibolites, the P–T–X dependence of their phase relationships is remarkably similar to that in metapelitic rocks. The mineral assemblages of Fe‐rich amphibolites are typically dominated by garnet‐ and staurolite‐bearing assemblages, whereas their more Mg‐rich counterparts contain chlorite and cordierite. Assemblages involving staurolite–hornblende can occur over a wide range of pressures (4–10 kbar) at temperatures of 560–650 °C; however, except in the more aluminous, iron‐rich compositions, they occupy a narrow pressure–temperature window. Thus, although their occurrence in ‘typical’ amphibolites may be indicative of relatively high pressure metamorphism, in more aluminous compositions their interpretation is less straightforward.

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Regional Tectonic Synthesis of Northwestern New England and Adjacent Quebec

Cited by 18 publications

References 0 publications

Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus

Gravity and magnetic anomalies of the Sutton Mountains region, Quebec and Vermont: expressions of rift volcanics related to the opening of Iapetus

Dunnage Melange and Subduction of the Protacadic Ocean Northeast Newfoundland

Amphibolites with staurolite and other aluminous minerals: calculated mineral equilibria in NCFMASH

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