Emplacement history and tectonic significance of the Cortlandt Complex, related plutons, and dike swarms in the Taconide Zone of southeastern New York based on K-Ar and Rb-Sr investigations

Ratcliffe, Nicholas M.; Armstrong, R. L.; Mose, Douglas G.; Seneschal, Ronald; Williams, N.; Baiamonte, Matthew J.

doi:10.2475/ajs.282.3.358

Cited by 17 publications

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“…At present there are no documented unequivocal Taconian plutons west of the Connecticut River, although several mafic plutons (e.g. Cortlandt Complex, NY, and Mt Prospect Complex, CT), like the granitoids above, appear to be immediately post-Taconian (Ratcliffe et al, 1982).…”

Section: H a R A C T E R I S T I C S Of T A C O N I A N M E T A M Omentioning

confidence: 86%

Contrasting styles of Taconian, Eastern Acadian and Western Acadian metamorphism, central and western New England

Armstrong

Tracy

Hames³

1992

Journal Metamorphic Geology

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The two major Early to Middle Palaeozoic tectonic/metamorphic events in the northern Appalachians were the Taconian (Middle to Late Ordovician) in central to western areas and the Acadian (Late Silurian to early Middle Devonian) in eastern to west-central areas. This paper presents a model for the Acadian orogenic event which separates the Acadian metamorphic realm into eastern and western belts based on distinctively different styles. We propose that the Acadian metamorphism in the east was the delayed consequence of Taconian back-arc lithospheric modification. East of the Taconian island arc, thick accumulations of Late Ordovician and Silurian sediments, coupled with plutons rising along a magmatic arc, produced crustal thermal conditions appropriate for anomalously high-T, low-P metamorphism accompanied by major crustal anatexis. In this zone, upward melt migration was coupled with subsequent E-W crustal shortening (possibly due to outboard collision with the Avalon terrane) to produce mechanical conditions that favoured formation of fold and thrust nappes and resultant tectonic thickening to the west (and probably to the east as well).The basis for the distinction between the Eastern and Western Acadian events lies in the contrasting styles of metamorphism accompanying each. Evidence for contrasting metamorphic styles consists of (1) estimated metamorphic field gradients (MFGs) based on thermobarometric studies, and (2) petrological evidence for contrasting P-T trajectories. West of the Acadian metamorphic front, the Taconian zone has an MFG in which peak temperatures of 400-600" C were reached at pressures of about 4-6 kbar, with both P and T increasing to the east. Near its western edge, the Western Acadian metamorphic overprint has a similar MFG to the Taconian, and is mainly discriminated by 4"Ar/"Ar dating and microtextural evidence. East of this narrow zone, the Western Acadian overprint is characterized by progressively higher temperatures (600-725" C) and pressures (6.5-10 kbar, or more) to the east, yielding an overall MFG that lies along, or slightly above, the kyanite-sillimanite boundary on a P-T diagram. There is little or no plutonism accompanying Western Acadian metamorphism.In contrast, thermobarometry in the Eastern Acadian, east of the Bronson Hill Belt, yields high-T, intermediate-P conditions for the highest grade rocks known in New England: T = 650-750" C, P = 4.5-6.5 kbar for granulite facies assemblages which apparently formed along an 'anticlockwise' P-T path. The Bronson Hill Belt lies geographically between the Eastern and Western Acadian zones and shows transitional petrological behaviour: anomalously high temperatures at intermediate pressures, but a 'clockwise' path with decompression cooling.Radiometric dating indicates peak Taconian conditions may have been achieved as early as 475 Ma in the Taconian hinterland and as late as 445Ma in the Taconian foreland (including the Taconic allochthons). Eastern Acadian magmatism may have started as early as 425 Ma, and most nappe-stage def...

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Section: H a R A C T E R I S T I C S Of T A C O N I A N M E T A M Omentioning

confidence: 86%

Contrasting styles of Taconian, Eastern Acadian and Western Acadian metamorphism, central and western New England

Armstrong

Tracy

Hames³

1992

Journal Metamorphic Geology

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“…± 5 Ma), Peach Lake Complex (450 ± 4 Ma), and Cortlandt Complex (446 ± 2 Ma; Ratcliffe, 1968Ratcliffe, , 1981Ratcliffe et al, 1982Ratcliffe et al, , 2012. Thus, the paleontologic and geochronologic data suggest that the final transport of the composite accreted rocks, at least in western Connecticut, occurred after ca.…”

Section: Research Papermentioning

confidence: 99%

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

et al. 2019

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U-Pb zircon geochronology by sensitive high-resolution ion microprobe–reverse geometry (SHRIMP-RG) on 11 plutonic rocks and two volcanic rocks from the Bronson Hill arc in western New Hampshire yielded Early to Late Ordovician ages ranging from 475 to 445 Ma. Ages from Oliverian Plutonic Suite rocks that intrude a largely mafic lower section of the Ammonoosuc Volcanics ranged from 474.8 ± 5.2 to 460.2 ± 3.4 Ma. Metamorphosed felsic volcanic rocks from within the Ammonoosuc Volcanics yielded ages of 460.1 ± 2.4 and 455.0 ± 11 Ma. Younger Oliverian Plutonic Suite rocks that either intrude both the upper and lower Ammonoosuc Volcanics or Partridge Formation ranged in age from 456.1 ± 6.7 Ma to 445.2 ± 6.7 Ma. These new data and previously published results document extended magmatism for >30 m.y. The ages, along with the lack of mappable structural discontinuities between the plutons and their volcanic cover, suggest that the Bronson Hill arc was part of a relatively long-lived composite arc. The Early to Late Ordovician ages presented here overlap with previously determined igneous U-Pb zircon ages in the Shelburne Falls arc to the west, suggesting that the Bronson Hill arc and the Shelburne Falls arc could be part of one, long-lived composite arc system, in agreement with the interpretation that the Iapetus suture (Red Indian Line) lies to the west of the Shelburne Falls–Bronson Hill arc system.

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“…Hobson (1964, p. 97) suggested that the pseudomorphs of kyanite(?) are sillimanite, and Reed & Jolly (1963) reported that cordierite pseudomorphs may occur, indicating a lower pressure (Fig. 6).…”

Section: Distribution and Estimates Of Temperature And Pressurementioning

confidence: 97%

“…The contact metamorphic aureole associated with the mafic to ultramafic CC contains silliman-ite+K-feldspar and, at lower grade, kyanite (Ratcliffe et al 1982. Tracy et al (1984) reported temperatures as great as 800-900°C and a pressure greater than 7 kbar for emery present as roof pendants and xenoliths.…”

Section: Distribution and Estimates Of Temperature And Pressurementioning

confidence: 99%

“…Younger plateau ages on biotite and hornblende from the GMM, BM and HHM are interpreted as cooling ages. As summarized by Ratcliffe et al (1982Ratcliffe et al ( , 1983, the Cortlandt plutonic complex (CC), which intruded near the regional metamorphic maximum and contact metamorphosed Cambrian and Ordovician rocks from the northern HHM and Manhattan Prong (MP), has been dated at 383-496 Ma by several isotopic methods. 4°Ar/aqAr plateau ages on biotite and muscovite from Dutchess County (DC), New York, range from 443 to 377 Ma (Bence & Rajamani 1972, Bence & McLelland 1976.…”

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confidence: 99%

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Arenig to Wenlock age metamorphism in the Appalachians

Laird¹

1988

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S U M M A R Y: Arenig to Wenlock age metamorphism is best defined in the western part of the Appalachian orogen but may well be preserved in some terranes to the E that are underlain by basement which is not N. American regional metamorphism is primarily medium pressure, but low-to medium-pressure facies series metamorphism also occurs in the central Appalachians, and high-pressure metamorphism is locally preserved in northern Vermont and adjacent Quebec. Metamorphic grade varies from prehnite-pumpellyite to granulite facies; the isograds are generally parallel to the regional NE structural trend. Delimitation of the isograds has been hampered by widespread polymetamorphism, uncertainties in interpretation of field and isotopic data, and the need for more detailed mapping and petrological studies.

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Emplacement history and tectonic significance of the Cortlandt Complex, related plutons, and dike swarms in the Taconide Zone of southeastern New York based on K-Ar and Rb-Sr investigations

Cited by 17 publications

References 0 publications

Contrasting styles of Taconian, Eastern Acadian and Western Acadian metamorphism, central and western New England

Contrasting styles of Taconian, Eastern Acadian and Western Acadian metamorphism, central and western New England

Geochronology of the Oliverian Plutonic Suite and the Ammonoosuc Volcanics in the Bronson Hill arc: Western New Hampshire, USA

Arenig to Wenlock age metamorphism in the Appalachians

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