Regional significance of new U–Pb age data for Neoproterozoic igneous units in Avalonian rocks of northern mainland Nova Scotia, Canada

1997 ◽  
Vol 134 (1) ◽  
pp. 113-120 ◽  
Author(s):  
J. BRENDAN MURPHY ◽  
J. DUNCAN KEPPIE ◽  
DON DAVIS ◽  
TOM E. KROGH
Keyword(s):  
Nova Scotia ◽  
Volcanic Arc ◽  
Cape Breton Island ◽  
North West ◽  
Cape Breton ◽  
Pan African ◽  
Appalachian Orogen ◽  
Back Arc ◽  
Age Range ◽  
Arc Deposition

Gondwanan Neoproterozoic tectonothermal events (Pan-African and Brasiliano) are represented in northern mainland of Nova Scotia by volcanic and sedimentary rocks assigned to the Jeffers and Georgeville groups and by gabbroic to granitoid plutons. These rocks comprise part of Avalonia, an exotic terrane in the Appalachian orogen that was deposited in an arc-related environment along the periphery of Gondwana prior to accretion to Laurentia. Lavas sampled in the basal units of the Jeffers and Georgeville groups yielded slightly discordant U–Pb zircon and monazite data that fall on chords with upper intercept ages of 628 Ma and 617.7±1.6 Ma, respectively. Syntectonic to late syntectonic plutons intruded into these groups yielded U–Pb zircon ages of 606.6±1.6 Ma and 603+9−5 Ma. The former intrusion also yielded a concordant titanite age of 607±3 Ma. When combined with previously published ages, these data indicate that the back-arc deposition recorded in these groups lasted 10–15 million years (628–613 Ma) and was closely followed by c. 613–595 Ma metamorphism, intrusion and heterogeneous strike-slip related deformation. Assuming no significant shuffling of fault blocks, the relative locations of the Cobequid–Antigonish back-arc basin and the southern Cape Breton Island volcanic arc are consistent with their genesis above a north-west-dipping subduction zone. The age range of arc-related magmatism in Nova Scotia is similar to that of Avalonian rocks in southeastern Newfoundland and Britain, lending support to hypotheses of Neoproterozoic linkages.

Birth of the Avalon arc in Nova Scotia, Canada: geochemical evidence for ∼700–630 Ma back-arc rift volcanism off Gondwana

1998 ◽  
Vol 135 (2) ◽  
pp. 171-181 ◽  
Author(s):  
J. D. KEPPIE ◽  
J. DOSTAL
Keyword(s):  
Nova Scotia ◽  
Volcanic Rocks ◽  
Benioff Zone ◽  
Calc Alkaline ◽  
Cape Breton Island ◽  
Mafic Rocks ◽  
Cape Breton ◽  
Arc Setting ◽  
Oceanic Island Basalts ◽  
Back Arc

Central Cape Breton Island in Nova Scotia, Canada, is host to ∼700–630 Ma felsic and associated mafic volcanic rocks that are relatively rare in other parts of the Avalon Composite Terrane, occurring elsewhere only in the Stirling Block of southern Cape Breton Island and in parts of eastern Newfoundland. The mafic rocks of central Cape Breton Island are typically intraplate tholeiitic basalts generated by melting of a garnet-bearing mantle source. They lack a continental trace element and εNd imprint although they were emplaced on continental crust; they resemble oceanic island basalts. Contemporaneous volcanism in the Stirling Block is calc-alkaline and formed in a volcanic arc setting. In the absence of evidence for an intervening trench complex or suture, it may be inferred that the central Cape Breton tholeiites formed in a back-arc setting relative to the Stirling Block. This rifting may represent the initial stages of separation of an Avalonian arc from western Gondwana. The arc rifted further between ∼630–610 Ma when the younger Antigonish-Cobequid back-arc basin formed. Subsequently, the extensional arc became convergent, telescoping the back-arc basin. Northwestward migration of calc-alkaline arc magmatism may be related to shallowing of the associated Benioff zone through time.

Geological correlations between Cape Breton Island and Newfoundland, northern Appalachian orogen

1998 ◽  
Vol 35 (11) ◽  
pp. 1252-1270 ◽  
Author(s):  
S M Barr ◽  
R P Raeside ◽  
C E White
Keyword(s):  
Sensu Stricto ◽  
Mobile Belt ◽  
Cape Breton Island ◽  
Small Areas ◽  
Isotopic Signatures ◽  
The North ◽  
Rock Types ◽  
Cape Breton ◽  
Appalachian Orogen ◽  
Back Arc

Geological correlations between Cape Breton Island and Newfoundland are apparent both in surface geology and at deeper crustal levels, based on similarities in Sm-Nd isotopic signatures. The Mira terrane of southeastern Cape Breton Island is part of the Avalon terrane sensu stricto and is composed of Neoproterozoic volcanic-sedimentary-plutonic belts and overlying Cambrian rocks directly comparable to those in the western part of the Newfoundland Avalon terrane. The Bras d'Or terrane is also mainly of Neoproterozoic age, but shows lithological and isotopic contrasts with the Mira terrane. Small areas of similar Neoproterozoic rocks occur in southern Newfoundland and to the north as inliers in the Exploits terrane. The Bras d'Or terrane and similar rocks in Newfoundland are interpreted to represent a peri-Gondwanan terrane where rocks of the Gander terrane were later formed. Hence this area is part of the Central Mobile Belt and distinct from Avalon terrane sensu stricto. The Aspy terrane is a complex area that may include fragments of Bras d'Or crust and components of the Gander, Exploits, and possibly Notre Dame terranes of Newfoundland. It formed by subduction and back-arc basin opening and closure during the Silurian to Early Devonian. The Blair River Inlier is a fragment of Grenvillian rocks, similar to those in the Grenvillian inliers in the Humber zone of western Newfoundland in terms of age, rock types, and isotopic composition. Silurian and Devonian promontory-promontory collision resulted in juxtaposition and stacking of these elements in Cape Breton Island, as in the Hermitage Flexure - Port aux Basques area of Newfoundland. Because the lower crust under Bras d'Or - Gander - Aspy terranes seems distinct from that under Avalon terrane sensu stricto, it is preferable to use the term peri-Gondwanan rather than Avalonian to refer to these areas.

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.

Frank Campbell MacIntosh, 24 December 1909 - 11 September 1992

1994 ◽  
Vol 40 ◽  
pp. 253-264 ◽  
Keyword(s):  
Nova Scotia ◽  
New England ◽  
Prince Edward Island ◽  
United Church Of Canada ◽  
Cape Breton Island ◽  
North West ◽  
The North ◽  
Cape Breton ◽  
One Year ◽  
North West Territories

The MacIntoshes were displaced from the Western Isles of Scotland by the Highland clearances at the end of the eighteenth century and like many of their compatriots moved to Nova Scotia. Around 1816 the Macintoshes were settled on a farm at Big Harbour Island on the Bras d’Or Lake of Cape Breton Island, that large detached part of Nova Scotia separated from the mainland by the narrow Straits of Canso - so narrow that they were frequently crossed by swimming deer. This part of Nova Scotia had a considerable resemblance to the old home in its landscape and its sea-tom ruggedness, which must have assuaged some of the pain of exile. Frank (who was always known as Hank) was born at Baddeck in Cape Breton on 24 December 1909, the son of the Reverend C.C. Macintosh, a well-known pastor of the United Church of Canada, who spoke and preached in Gaelic in the Canadian Maritimes and in New England. His mother Beenie Matheson, also of Scottish origin, came from Prince Edward Island. She had trained as a teacher and had moved to the north-west territories as a pioneer. As a child Hank frequently went visiting with his father in the horse and buggy. He was a precocious child and taught himself to read at the age of three - largely from the Encyclopedia Britannica - becoming especially interested in the geographical places described therein. At nine he was driving the family Model T. He was very proud of the fact that when he was just one year old, Alexander Graham Bell dandled him on his knee at his home in Beinn Bhreagh.

Cape Breton ruby, a new Canadian gemstone discovery, Cape Breton Island, Nova Scotia

2007 ◽  
Vol 30 (5) ◽  
pp. 279-286 ◽  
Author(s):  
David J. Mossman ◽  
James D. Duivenvoorden ◽  
Fenton M. Isenor
Keyword(s):  
Nova Scotia ◽  
Cape Breton Island ◽  
Cape Breton
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