The Taconian orogeny in southern New England: Nd-isotope evidence against addition of juvenile components

1996 ◽  
Vol 33 (12) ◽  
pp. 1612-1627 ◽  
Author(s):  
B. Bock ◽  
S. M. McLennan ◽  
G. N. Hanson
Keyword(s):  
New England ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Nd Isotope ◽  
Middle Ordovician ◽  
Southern New England ◽  
Isotope Evidence ◽  
Juvenile Crust ◽  
Plutonic Rocks ◽  
Laurentian Margin

Nd-isotope data for pre-Taconian (meta)sedimentary and igneous rocks, syn-Taconian (meta)sedimentary rocks, and Late Ordovician–Silurian plutonic rocks indicate that the Ordovician Taconian orogeny did not add significant amounts of juvenile crust to the Laurentian margin in southern New England. Nd-isotope compositions of Grenvillian crust and Late Proterozoic to Early Cambrian rift sediments range from εNd of −3.1 to −6.6 at 450 Ma. Sedimentary rocks deposited during the Cambrian and the early Middle Ordovician, which represent the drift stage of Laurentia, and earliest Taconian sedimentary rocks show more negative εNd(450 Ma), with a range from −11.7 to −13.3. Sedimentary rocks deposited in response to the Taconian orogeny have uniform εNd(450 Ma) values of about −8. Middle to Late Ordovician and Permian plutonic rocks from southwestern Connecticut have εNd(450 Ma) values of −2 to −5, which indicates that these rocks contain older crustal components. Rocks with juvenile Nd characteristics are the early Paleozoic Maltby Lake Volcanics (εNd(450 Ma) +8) from southwestern Connecticut, and Middle Ordovician igneous samples from the Hawley Formation (εNd(450 Ma) +6 to −0.6) in Massachusetts.

The Ordovician volcanics of the Elmtree–Belledune inlier and their relationship to volcanics of the northern Miramichi Highlands, New Brunswick

1992 ◽  
Vol 29 (7) ◽  
pp. 1430-1447 ◽  
Author(s):  
J. A. Winchester ◽  
C. R. van Staal ◽  
J. P. Langton
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Late Ordovician ◽  
Igneous Rocks ◽  
Volcanic Arc ◽  
Middle Ordovician ◽  
Marginal Basin ◽  
Tectonic Mélange ◽  
Back Arc

An investigation of the geology and chemistry of the basic igneous rocks in the Elmtree and Belledune inliers in northern New Brunswick shows that the bulk of the Middle Ordovician rocks of the ophiolitic Fournier Group are best interpreted as the products of volcanism and sedimentation in an extensive ensimatic back-arc basin southeast of a volcanic arc. The oceanic back-arc-basin igneous rocks form the basement to renewed arc-related basaltic volcanism in late Middle to Late Ordovician time. The Fournier Group is separated from the structurally-underlying, shale-dominated Elmtree Formation of the Tetagouche Group by an extensive tectonic melange, which incorporates lenses of serpentinite, mafic volcanic rocks, and sedimentary rocks of both the Tetagouche and Fournier groups. The mafic volcanic rocks in the Elmtree Formation correlate best with those intercalated with the lithologically similar sediments of the Llandeilian–Caradocian Boucher Brook Formation in the northern Miramichi Highlands. The melange and the present structural amalgamation of the Tetagouche and Fournier groups result from closure of the marginal basin by northward-directed subduction at the end of the Ordovician. Most mafic suites in the Elmtree and Belledune inliers can be chemically correlated with similar suites in the northern Miramichi Highlands, showing that the two areas are not separated by a terrane boundary.

The extent of juvenile crust in the Grenville Province: Nd isotope evidence

2009 ◽  
Vol 122 (5-6) ◽  
pp. 870-883 ◽  
Author(s):  
A. P. Dickin ◽  
R. H. McNutt ◽  
C. Martin ◽  
A. Guo
Keyword(s):  
Grenville Province ◽  
Nd Isotope ◽  
Isotope Evidence ◽  
Juvenile Crust

Sr and Nd isotope evidence for successive crustal contamination of Slieve Gullion ring-dyke magmas, Co. Armagh, Ireland

2005 ◽  
Vol 142 (6) ◽  
pp. 659-668 ◽  
Author(s):  
VALENTIN R. TROLL ◽  
JANE P. CHADWICK ◽  
ROBERT M. ELLAM ◽  
SUSAN Mc DONNELL ◽  
C. HENRY EMELEUS ◽  
...  
Keyword(s):  
Country Rock ◽  
Sedimentary Rocks ◽  
Crustal Contamination ◽  
Nd Isotope ◽  
Second Stage ◽  
Rock Types ◽  
Isotope Evidence ◽  
Lower Palaeozoic ◽  
And Storage ◽  
Ring Dyke

The Palaeogene Slieve Gullion Igneous Centre in southern Armagh, Northern Ireland, consists of a layered central intrusive complex surrounded by a prominent and slightly older ring-dyke that intrudes both Lower Palaeozoic sedimentary rocks and the Caledonian Newry Granodiorite pluton (452 Ma). The ring-dyke comprises two major rock types: porphyritic felsite and porphyritic granophyre. We analysed both ring-dyke lithologies, both types of country rock, and a local Palaeogene basalt dyke sample for Sr and Nd isotopes. Trace element and whole rock data for this suite suggest that there are two distinct groups of both felsite and granophyre: one Si-rich and one Si-poor, most likely representing two magmas from a zoned chamber and their mushy chamber wall equivalents (McDonnell et al. 2004). Isotope data show the low-Si rocks to be higher in radiogenic Sr than the high-Si rocks, which is inconsistent with a simple AFC-scenario of increasing sediment assimilation with higher degrees of differentiation. However, using MORB-type basalt as a starting composition, the low-Si ring-dyke rocks can be modelled through AFC with Lower Palaeozoic sedimentary rock as the contaminant. The decreasing 87Sr/86Sr trend from low-Si to high-Si dyke rocks, in turn, represents a second stage of contamination. Selective assimilation of the most fusible portions of Newry Granodiorite, which is lower in radiogenic Sr than the local sedimentary rocks, appears to be the most plausible solution. The Sr and Nd data are consistent with (a) at least a two-stage contamination history during upper crustal residence and storage, whereby fractionating magmas of basaltic and intermediate composition are contaminated by local sedimentary rocks, giving rise to rhyolite magmas that experience additional shallow contamination by Newry Granodiorite, and (b) a zoned rhyolite magma chamber where high-Si magma is stored in the upper part of the chamber where crystallization and crustal contamination are most extensive.

Tectonic evolution and significance of Silurian – Early Devonian hinterland-directed deformation in the internal Humber zone of the southern Quebec Appalachians

2003 ◽  
Vol 40 (2) ◽  
pp. 255-268 ◽  
Author(s):  
Sébastien Castonguay ◽  
Alain Tremblay
Keyword(s):  
New England ◽  
Tectonic Evolution ◽  
Normal Faults ◽  
Early Devonian ◽  
Middle Ordovician ◽  
Tectonic History ◽  
History Of ◽  
Connecticut Valley ◽  
Laurentian Margin ◽  
Nappe Emplacement

In the southern Quebec Appalachians, the early tectonic history of the Laurentian margin (Humber zone) comprises foreland-propagating, northwest-directed thrust faulting, nappe emplacement, and regional prograde metamorphism in response to the obduction of large ophiolitic nappes during the Taconian orogeny. In the internal Humber zone, this event is dated at 462 ± 3 Ma (late Middle Ordovician), which is interpreted to represent the timing of near-peak Taconian metamorphism. Superimposed hinterland-directed structures are accompanied by retrograde metamorphism and consist of back thrusts and normal faults, which respectively delimit the northwestern and southeastern limbs of the Sutton and Notre-Dame mountains anticlinoria, both salient structures of the internal Humber zone of southern Quebec. Geochronologic data on the timing of hinterland-directed deformation vary from 431 to 411 Ma. Two tectonic models are presented and discussed, which may account for the Silurian – Early Devonian evolution of the Laurentian margin: (1) back thrusting and syn- to post-compressional crustal extension in response to the tectonic wedging of basement-cored duplexes inducing delamination of supracrustal rocks; (2) tectonic exhumation of the internal Humber zone by extensional collapse. Evidence for Silurian – Early Devonian extensional tectonism in the Humber zone provides the basement infrastructures necessary for the creation and the onset of sedimentation in the Gaspé Belt basins (e.g., Connecticut Valley – Gaspé synclinorium). Several structural, metamorphic features in the internal Humber zone of the northwestern New England Appalachians yield analogous characteristics with those of southern Quebec and may have shared a similar Silurian – Early Devonian tectonic evolution.

Age and tectonic setting of the Nesåa Batholith: implications for Ordovician arc development in the Caledonides of Central Norway

2003 ◽  
Vol 140 (5) ◽  
pp. 573-594 ◽  
Author(s):  
G. B. MEYER ◽  
T. GRENNE ◽  
R. B. PEDERSEN
Keyword(s):  
Rare Earth ◽  
Partial Melting ◽  
Continental Margin ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Shear Zones ◽  
Late Ordovician ◽  
Magma Ascent ◽  
Middle Ordovician ◽  
Laurentian Margin

New U–Pb zircon dating yields a crystallization age of 458±3 Ma for the largely gabbroic Grøndalsfjell Intrusive Complex in the Gjersvik Nappe of the Caledonian Upper Allochthon in Scandinavia. This is identical, within error, to the age of the adjacent Møklevatnet Complex that is dominated by quartz monzodiorite (456±2 Ma), and the two intrusive suites may be regarded as members of a composite intrusion here referred to as the Nesåa Batholith. Mafic members of this calc-alkaline batholith are characterized by slightly positive εNd–εSr values, marked enrichment of the light rare earth elements and high Th/Yb ratios suggestive of a subduction-modified mantle source. The I-type granitoids have similar isotope values and highly fractionated rare earth element patterns, and are interpreted as products from partial melting of garnet-bearing mafic rocks. The Nesåa Batholith intruded a previously deformed, 483 Ma or older, metavolcanic sequence of oceanic arc affinity. The margins of the pluton show evidence for synkinematic emplacement, which is tentatively interpreted in terms of magma ascent controlled by deep-seated shear zones. Further uplift and exhumation of the crystallized plutons was followed by rapid deposition of batholith-derived conglomerates and arkoses in a marginal basin represented by the Limingen Group. The age of the Nesåa Batholith fills the gap in reported ages for Caledonian magmatism, between the Early to Middle Ordovician, oceanic to continental margin type, arc sequences of Laurentian palaeotectonic affinity, and the Late Ordovician–Early Silurian batholith complexes of interpreted Laurentian margin affinity. It is interpreted as an early phase of the more extensive plutonism recorded in the Bindal Batholith of the Uppermost Allochthon to the west. Our model implies that the Early Ordovician oceanic arc sequences of the Gjersvik Nappe were deformed and accreted on to Laurentian margin lithologies prior to Late Ordovician times. This composite crustal assemblage was the source for the voluminous quartz monzodioritic intrusions of the Nesåa Batholith, which formed by partial melting due to ponding of subduction-related mantle derived mafic magmas either within or at the base of the active continental margin.

Where is the Iapetus suture in northern New England? A study of the Ammonoosuc Volcanics, Bronson Hill terrane, New Hampshire1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

2012 ◽  
Vol 49 (1) ◽  
pp. 189-205 ◽  
Author(s):  
Michael J. Dorais ◽  
Miles Atkinson ◽  
Jon Kim ◽  
David P. West ◽  
Gregory A. Kirby
Keyword(s):  
New England ◽  
Subduction Zone ◽  
Volcanic Rocks ◽  
Middle Ordovician ◽  
Isotopic Signatures ◽  
Basement Rocks ◽  
Iapetus Ocean ◽  
Maritime Canada ◽  
Laurentian Margin ◽  
Back Arc

The ∼470 Ma Ammonoosuc Volcanics of the Bronson Hill terrane of New Hampshire have back-arc basin basalt compositions. Major and trace element compositions compare favorably to coeval volcanic rocks in the Miramichi Highlands of New Brunswick and the Munsangan and Casco Bay volcanics of Maine, back-arc basin basalts of known peri-Gondwanan origins. Additionally, the Ammonoosuc Volcanics have Nd and Pb isotopic compositions indicative of peri-Gondwanan provenance. Thus, the Ammonoosuc Volcanics correlate with Middle Ordovician, peri-Gondwanan, Tetagouche–Exploits back-arc rocks of eastern New England and Maritime Canada. This correlation indicates that the Red Indian Line, the principle Iapetus suture, lies along the western margin of the Bronson Hill terrane. However, the younger (∼450 Ma) Oliverian Plutonic Suite rocks that intruded the Ammonoosuc Volcanics, forming domes along the core of the Bronson Hill anticlinorium, have Laurentian isotopic signatures. This suggests that the Ammonoosuc Volcanics were thrust westwardly over the Laurentian margin, and that Laurentian basement rocks are present under the Bronson Hill terrane. A plausible explanation for these relationships is that an easterly dipping subduction zone formed the Ammonoosuc Volcanics in the Tetagoughe–Exploits oceanic tract, just east of the coeval Popelogan arc. With the closure of the Iapetus Ocean, this terrane was thrust over the Laurentian margin. Subsequent to obduction of the Ammonoosuc Volcanics, subduction polarity flipped to the west, with the Oliverian arc resulting from a westerly dipping subduction zone that formed under the Taconic Orogeny-modified Laurentian margin.

Detrital zircon ages and the origins of the Nashoba terrane and Merrimack belt in southeastern New England, USA

2021 ◽  
Vol 57 ◽  
pp. 343-396
Author(s):  
J. Christopher Hepburn ◽  
Yvette D. Kuiper ◽  
Kristin J. McClary ◽  
MaryEllen L. Loan ◽  
Michael Tubrett ◽  
...  
Keyword(s):  
New England ◽  
Detrital Zircon ◽  
Inductively Coupled Plasma ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Mass Spectrometry Analysis ◽  
Zircon Age ◽  
Spectrometry Analysis ◽  
Middle Ordovician ◽  
Nashoba Terrane

The fault-bounded Nashoba–Putnam terrane, a metamorphosed early Paleozoic, Ganderian arc/back-arc complex in SE New England, lies between rocks of Avalonian affinity to the southeast and middle Paleozoic sedimentary rocks, interpreted as cover on Ganderian basement, in the Merrimack belt to the northwest. U–Pb detrital zircon laser ablation inductively coupled plasma mass spectrometry analysis were conduced on six samples from the Nashoba terrane in Massachusetts and seven samples associated with the Merrimack belt in Massachusetts and SE New Hampshire to investigate their depositional ages and provenance. Samples from the Nashoba terrane yielded major age populations between ~560 and ~540 Ma, consistent with input from local sources formed during the Ediacaran–Cambrian Penobscot orogenic cycle and its basement rocks. Youngest detrital zircons in the terrane, however, are as young as the Early to Middle Ordovician. Six formations from the Merrimack belt were deposited between ~435 and 420 Ma based on youngest zircon age populations and crosscutting plutons, and yielded large ~470–443 Ma age populations. Three of these formations show only Gondwanan provenance. Three others have a mixed Gondwanan-Laurentian signal, which is known to be typical for younger and/or more westerly sedimentary rocks and may indicate that they are the youngest deposits in the Merrimack belt (late Silurian to early Devonian) and/or have been deposited in the equivalent of the more westerly Central Maine basin. Detrital zircon age populations from the Tower Hill Formation, along the faulted contact between the Merrimack belt and Nashoba terrane, are different from either of these tectonic domains and may indicate that the boundary is complex.

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