Late Devonian – Early Carboniferous volcanism in western Cape Breton Island, Nova Scotia

1984 ◽  
Vol 21 (7) ◽  
pp. 762-774 ◽  
Author(s):  
Marie-Claude Blanchard ◽  
Rebecca A. Jamieson ◽  
Elizabeth B. More
Keyword(s):  
Tectonic Setting ◽  
Early Carboniferous ◽  
Alluvial Fan ◽  
Late Devonian ◽  
Fluvial Sediments ◽  
Western Cape ◽  
Cape Breton Island ◽  
The North ◽  
Cape Breton ◽  
Geochemical Studies

The Fisset Brook Formation of western Cape Breton Island and its equivalents at MacMillan Mountain and the north Baddeck River are examples of Late Devonian and Early Carboniferous volcanic sequences associated with the formation of post-Acadian successor basins in the northeastern Appalachians. They consist of bimodal basalt–rhyolite suites interbedded with alluvial fan, lacustrine, and rare fluvial sediments. The earliest volcanic products are rhyolites and somewhat evolved basalts associated with coarse sediments, followed by tholeiitic to transitional basalt flows interlayered with lacustrine-type deposits. Geochemical studies on the Fisset Brook Formation indicate extensive remobilization of alkalies, Ca, Rb, and Sr, making these elements inappropriate for determining tectonic setting or magmatic affinity. Use of less mobile elements (Ti, Nb, Y, and Zr) suggests that the basalts are tholeiitic and that the apparent alkalinity of the type section lavas is a result of alteration. We conclude that volcanism in western Cape Breton Island started at MacMillan Mountain and migrated westwards, probably towards the centre of the deepening Magdalen Basin.

Petrology, age, and tectonic setting of the rapakivi-bearing Margaree pluton, Cape Breton Island, Canada: evidence for a Late Devonian posttectonic cryptic silicic-mafic magma chamber

2020 ◽  
Vol 57 (9) ◽  
pp. 1011-1029
Author(s):  
Gabriel Sombini dos Santos ◽  
Sandra M. Barr ◽  
Chris E. White ◽  
Deanne van Rooyen
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Tectonic Setting ◽  
Mafic Magma ◽  
Coarse Grained ◽  
Late Devonian ◽  
Cape Breton Island ◽  
Cape Breton

The Margaree pluton extends for >40 km along the axis of the Ganderian Aspy terrane of northern Cape Breton Island, Nova Scotia. The pluton consists mainly of coarse-grained megacrystic syenogranite, intruded by small bodies of medium-grained equigranular syenogranite and microgranite porphyry, all locally displaying rapakivi texture. The three rock types have similar U–Pb (zircon) ages of 363 ± 1.6, 364.8 ± 1.6, and 365.5 ± 3.3 Ma, respectively, consistent with field and petrological evidence that they are coeval and comagmatic. The rare earth elements display parallel trends characterized by enrichment in the light rare earth elements, flat heavy rare earth elements, moderate negative Eu anomalies, and, in some cases, positive Ce anomalies. The megacrystic and rapakivi textures are attributed to thermal perturbation in the magma chamber caused by the mixing of mafic and felsic magma, even though direct evidence of the mafic magma is mainly lacking at the current level of exposure. Magma evolution was controlled by fractionation of quartz, K-feldspar, and Na-rich plagioclase in molar proportions of 0.75:0.12:0.13. The chemical and isotopic (Sm–Nd) signature of the Margaree pluton is consistent with the melting of preexisting continental crust that was enriched in heat-producing elements, likely assisted by intrusion of mantle-derived mafic magma during Late Devonian regional extension. The proposed model involving magma mixing at shallow crustal levels in a cryptic silicic-mafic magma chamber during post-Acadian extension is consistent with models for other, better exposed occurrences of rapakivi granite in the northern Appalachian orogen.

The age of igneous and metamorphic events in the western Cape Breton Highlands, Nova Scotia

1986 ◽  
Vol 23 (12) ◽  
pp. 1891-1901 ◽  
Author(s):  
R. A. Jamieson ◽  
O. van Breemen ◽  
R. W. Sullivan ◽  
K. L. Currie
Keyword(s):  
Metamorphic Rocks ◽  
Western Cape ◽  
Cape Breton Island ◽  
Late Proterozoic ◽  
The North ◽  
Cape Breton ◽  
Gneiss Complex ◽  
Form Part ◽  
Plutonic Rocks ◽  
High Level

Plutonic rocks of four different ages have been recognized in the Cape Breton Highlands on the basis of U–Pb dating of zircons. Two plutons, the North Branch Baddeck River leucotonalite [Formula: see text] and the Chéticamp pluton (550 ± 8 Ma), give dates that fall within the range of Late Proterozoic to Cambrian ages considered characteristic of the Avalon tectonostratigraphic zone of the eastern Appalachians. Late Ordovician to Silurian tonalite (Belle Côte Road orthogneiss, 433 ± 20 Ma) was metamorphosed, deformed, and incorporated into the central Highlands gneiss complex by approximately 370–395 Ma. High-level subvolcanic plutons (Salmon Pool pluton, [Formula: see text]) postdate all metamorphic rocks in the area. The presence of the older plutons is consistent with interpretation that the Cape Breton Highlands form part of the Avalon zone, but the presence of Ordovician–Silurian plutonic rocks and Devonian amphibolite-facies metamorphism is anomalous in comparison with the Avalon zone of Newfoundland and southeastern Cape Breton Island. Terranes with similar Late Proterozoic to mid-Paleozoic plutonic and metamorphic histories form a discontinuous belt along the northwest side of the Avalon zone southwest of Cape Breton Island. These rocks probably reflect events during and after the accretion of the Avalon zone to North America.

scholarly journals Age and tectonic setting of granitoid plutons in the Chéticamp belt, western Cape Breton Island, Nova Scotia, Canada

2017 ◽  
Vol 54 (1) ◽  
pp. 88-109 ◽  
Author(s):  
L.R. Slaman ◽  
S.M. Barr ◽  
C.E. White ◽  
D. van Rooyen
Keyword(s):  
Inductively Coupled Plasma ◽  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Geological Mapping ◽  
Western Cape ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Isotopic Analyses ◽  
Plutonic Belt ◽  
Late Neoproterozoic

Geological mapping in the Chéticamp granitoid belt in combination with petrographic and geochemical studies and U–Pb (zircon) dating by laser ablation inductively coupled plasma mass spectrometry have resulted in major reinterpretation of the geology in the western part of the Ganderian Aspy terrane of Cape Breton Island. Nine new U–Pb (zircon) ages show that the former “Chéticamp pluton” consists of 10 separate plutons of five different ages: late Neoproterozoic (ca. 567 Ma), Cambrian–Ordovician (490–482 Ma), Ordovician–Silurian (442–440 Ma), mid-Silurian (ca. 428 Ma), and late Devonian (366 Ma). The three late Neoproterozoic granodioritic to monzogranitic plutons are older than the adjacent metavolcanic and metasedimentary rocks of the Jumping Brook Metamorphic Suite, whereas the tonalitic to quartz dioritic Cambrian–Ordovician plutons intruded those metamorphic rocks. Petrographic characteristics and approximately 100 whole-rock chemical analyses show that with the exception of the mid-Silurian Grand Falaise alkali-feldspar granite, which has A-type within-plate characteristics, the plutonic units have calc-alkaline affinity and were emplaced in a volcanic-arc tectonic setting. These results are evidence that fragments of a long history of episodic subduction-related magmatism and terrane collision are preserved in this small part of Ganderia. Eight new Sm–Nd isotopic analyses are consistent with the Ganderian affinity of the Chéticamp plutonic belt. The ca. 490–482 Ma plutons are the first direct evidence in Cape Breton Island for the Penobscottian event recognized in the Exploits Subzone of central Newfoundland and in New Brunswick. However, the structural relationship of the Chéticamp plutonic belt to the rest of the Aspy and Bras d’Or terranes remains enigmatic, as is the apparent absence of effects of Devonian deformation and metamorphism in the older plutonic units.

The Cheticamp pluton: a Cambrian granodioritic intrusion in the western Cape Breton Highlands, Nova Scotia

1986 ◽  
Vol 23 (11) ◽  
pp. 1686-1699 ◽  
Author(s):  
Sandra M. Barr ◽  
Alan S. Macdonald ◽  
John Blenkinsop
Keyword(s):  
Nova Scotia ◽  
Chemical Compositions ◽  
Western Cape ◽  
Fractionation Process ◽  
Cape Breton Island ◽  
Stratigraphic Unit ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Appalachian Orogen

The Cheticamp pluton consists of biotite granodiorite (locally megacrystic) in the north and museovite–biotite granodiorite in the south, in probable faulted contact. These two rock types, especially the biotite granodiorite, show a broad range in modal and chemical compositions. They are interpreted to be cogenetic, with the museovite–biotite grandiorite derived from the biotite granodiorite by crystal fractionation involving mafic minerals, plagioclase, and sphene. The overall peraluminous composition of the suite resulted from the fractionation process, probably enhanced by alteration, rather than from derivation from peraluminous source rocks.A seven-point, whole-rock, Rb–Sr isochron indicates an age of 525 ± 40 Ma. The pluton intruded dioritic rocks and quartzo-feldspathic gneisses, thus indicating Precambrian ages for these units. It probably also postdates the Western Highlands volcanic–sedimentary complex, a major undated stratigraphic unit in the Cape Breton Highlands. Although the age overlaps the range of Rb–Sr ages from plutons of the Avalon Terrane of the Appalachian orogen, the geological setting of the Cheticamp pluton differs from that of true Avalonian plutons, such as those in southeastern Cape Breton Island.

scholarly journals Field relations, age, and tectonic setting of metamorphic and plutonic rocks in the Creignish Hills – North Mountain area, southwestern Cape Breton Island, Nova Scotia, Canada

2016 ◽  
Vol 52 ◽  
pp. 037 ◽  
Author(s):  
Chris E. White ◽  
Sandra M. Barr ◽  
Donald W. Davis ◽  
David S. Swanton ◽  
John W.F. Ketchum ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Passive Margin ◽  
Mountain Areas ◽  
Mountain Area ◽  
Cape Breton Island ◽  
Metasedimentary Rocks ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Depositional Age

 The Creignish Hills and North Mountain areas of southwestern Cape Breton Island consist mostly of Neoproterozoic rocks typical of the Ganderian Bras d’Or terrane. U-Pb ages presented here for detrital zircon in the Blues Brook Formation of the Creignish Hills confirm a depositional age no greater than about 600 Ma. Although it is possible that some components of the formation are much older, similarities in rock types and field relations suggest that this is not the case. It is likely that the equivalent Malagawatch Formation of the North Mountain area, as well as high-grade metasedimentary rocks of the Melford Formation and Chuggin Road complex in the Creignish Hills and Lime Hill gneiss complex in the North Mountain area, represent the same or stratigraphically equivalent units as the Blues Brook Formation. The minimum ages of all of these units are constrained by cross-cutting syn- and post-tectonic plutons with ages mostly between 565 and 550 Ma, indicating that sediments were deposited, regionally metamorphosed, deformed, and intruded by plutons in less than 40–50 million years. The assemblage of pelitic, psammitic, and carbonate rocks indicates that a passive margin in a tropical climate was quickly changed to an active Andean-type continental margin in which voluminous calcalkaline dioritic to granitic plutons were emplaced. This sedimentary and tectonic history is characteristic of the Bras d’Or terrane and is shared by its likely correlative, the Brookville terrane in southern New Brunswick. 

Chronology of Devonian to early Carboniferous rifting and igneous activity in southern Magdalen Basin based on U-Pb (zircon) dating

2002 ◽  
Vol 39 (8) ◽  
pp. 1219-1237 ◽  
Author(s):  
Greg R Dunning ◽  
Sandra M Barr ◽  
Peter S Giles ◽  
D Colin McGregor ◽  
Georgia Pe-Piper ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Fault Zone ◽  
Middle Devonian ◽  
Volcanic Rocks ◽  
Early Carboniferous ◽  
Late Devonian ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Igneous Activity ◽  
Age Determinations

Fifteen U–Pb (zircon) radiometric age determinations have been made on igneous rocks of Middle Devonian to Early Carboniferous age from the southern margin of the Magdalen basin in Cape Breton Island and northern mainland Nova Scotia. Volcanic rocks interbed with early rift-basin sedimentary rocks with some palynological biostratigraphy; dated intrusive rocks cut these sedimentary units. Our biostratigraphically constrained ages are in close agreement with the current Devonian time scale. Combined with previously published data, the age determinations show that igneous activity occurred in four pulses: Middle Devonian (390–385 Ma), early Late Devonian (375–370 Ma), latest Devonian to early Tournaisian (365–354 Ma), and late Tournaisian to early Visean (ca. 339 Ma). Middle Devonian (385–389 Ma) volcanic rocks are confined to the Guysborough Group. The Fisset Brook Formation (basalt and minor rhyolite) in the type area and elsewhere in Cape Breton Island and northern mainland Nova Scotia is Late Devonian (ca. 373 Ma), whereas the biostratigraphically distinct succession at Lowland Cove is younger (365 Ma). These Late Devonian rocks are synchronous with plutonism in the Cape Breton Highlands and the Meguma terrane. In the Cobequid Highlands, rhyolite of the Fountain Lake Group was synchronous with Horton Group deposition and with widespread granite plutons (362–358 Ma) emplaced during shear on the Cobequid fault zone. The overlying Diamond Brook Formation basalts are slightly younger (355 Ma). Late Tournaisian – early Visean mafic intrusions and minor basalt occur along the Cobequid – Chedabucto fault zone and in a belt from southern New Brunswick through Prince Edward Island to southwestern Cape Breton Island.

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