scholarly journals Reactivation of the Eastern Highlands Shear Zone, Cape Breton Island, Appalachian Orogen

2019 ◽  
Author(s):  
N Piette-Lauzière ◽  
R Graziani ◽  
K P Larson ◽  
D A Kellett
Keyword(s):  
Shear Zone ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Appalachian Orogen ◽  
Eastern Highlands

Structural evolution and tectonic significance of the Eastern Highlands shear zone in Cape Breton Island, the Canadian Appalachians

1995 ◽  
Vol 32 (5) ◽  
pp. 545-554 ◽  
Author(s):  
Shoufa Lin
Keyword(s):  
Shear Zone ◽  
Structural Evolution ◽  
Greenschist Facies ◽  
Amphibolite Facies ◽  
Movement Direction ◽  
Cape Breton Island ◽  
Cape Breton ◽  
Shear Sense ◽  
Eastern Highlands ◽  
Canadian Appalachians

The Eastern Highlands shear zone in Cape Breton Island of the Canadian Appalachians is characterized by an amphibolite-facies deformation zone over 5 km wide overprinted by a greenschist-facies mylonite zone about 1 km wide. Deformation zones in both metamorphic grades dip steeply to the southeast with movement direction pitching steeply to the southwest, and shear sense indicators indicate the same sense of shear, that is, an east-over-west dip-slip movement with minor sinistral strike-slip component. Deformation in both conditions is constrained to the Late Silurian to Early Devonian (mainly Late Silurian). It is suggested that the greenschist-facies deformation represents the last stage of a single episode of deformation that occurred initially under amphibolite-facies conditions. The west-vergent shearing along the shear zone is antithetic to the westward subduction that led to the Silurian continent-continent collision, which is interpreted by tectonic wedging in this part of the Canadian Appalachians.

Geology and tectonic development of the Bras d'Or suspect terrane, Cape Breton Island, Nova Scotia

1990 ◽  
Vol 27 (10) ◽  
pp. 1371-1381 ◽  
Author(s):  
Robert P. Raeside ◽  
Sandra M. Barr
Keyword(s):  
Sedimentary Rocks ◽  
Early Cambrian ◽  
Significant Component ◽  
Southeastern Part ◽  
Cape Breton Island ◽  
Late Proterozoic ◽  
Cape Breton ◽  
Appalachian Orogen ◽  
Tectonic Development ◽  
Eastern Highlands

The Bras d'Or Terrane is defined in Cape Breton Island and consists of four distinctive components, (i) Low-pressure, regionally metamorphosed aluminous and calcareous gneiss of the Proterozoic Bras d'Or metamorphic suite is restricted to the southeastern part of the terrane. (ii) Late Proterozoic clastic-volcanic-carbonate units (Blues Brook, Malagawatch, McMillan Flowage, and Benacadie Brook formations, and Barachois River and Bateman Brook metamorphic suites) occur throughout the terrane and are generally at low metamorphic grades, although sillimanite grade has locally been achieved, (iii) A suite of 555–565 Ma calc-alkalic dioritic to granitic plutons was emplaced at pressures ranging from about 900 to less than 100 MPa. (iv) Early Ordovician granitic plutonism and Ordovician 40Ar/39Ar ages record regional heating.The Bras d'Or Terrane docked with the Mira Terrane to the southeast no earlier than the Ordovician. Cambro-Ordovician sedimentary rocks of the Mira Terrane appear locally to be thrust over the Bras d'Or Terrane. Mississippian sedimentary rocks overlap both terranes. The present boundary, the Macintosh Brook Fault, is mainly a Carboniferous feature. Docking with the Aspy Terrane to the northwest occurred along the Eastern Highlands shear zone and is constrained by a 375 Ma stitching pluton, the Black Brook Granitic Suite. Docking may have been initiated as early as 415 Ma, as indicated by reset 40Ar/39Ar ages near the boundary. The three Proterozoic components of the Bras d'Or Terrane have been recognized in the Brookville Terrane of southern New Brunswick, and Late Proterozoic gneiss, Late Proterozoic – early Cambrian calc-alkalic plutons and Ordovician granitic plutons have been reported in parts of the Hermitage Flexure of southern Newfoundland. The Bras d'Or Terrane may therefore be a regionally significant component of the northern Appalachian Orogen.

scholarly journals Field mapping of the Eastern Highlands Shear Zone, Cape Breton Island, Nova Scotia

2018 ◽  
Author(s):  
N Piette-Lauzière ◽  
K P Larson ◽  
D A Kellett
Keyword(s):  
Nova Scotia ◽  
Shear Zone ◽  
Cape Breton Island ◽  
Field Mapping ◽  
Cape Breton ◽  
Eastern Highlands

Relationship between the Aspy and Bras d'Or "terranes" in the northeastern Cape Breton Highlands, Nova Scotia

1993 ◽  
Vol 30 (9) ◽  
pp. 1773-1781 ◽  
Author(s):  
Shoufa Lin
Keyword(s):  
Shear Zone ◽  
Sedimentary Rocks ◽  
The West ◽  
Precambrian Rocks ◽  
Late Precambrian ◽  
Cape Breton ◽  
Basal Conglomerate ◽  
Back Arc ◽  
Eastern Highlands ◽  
Basin System

According to previous interpretations, the Eastern Highlands shear zone separates Ordovician–Silurian volcano-sedimentary rocks to the west (Cheticamp Lake Gneiss of the Aspy "terrane") from late Precambrian sedimentary rocks and dioritic – tonalitic plutons and Early Ordovician granite to the east (Bras d'Or "terrane"). New mapping discovered a basal conglomerate of the Cheticamp Lake Gneiss that rests on deformed diorite of the Bras d'Or "terrane" and contains clasts similar or identical to rocks of the Bras d'Or "terrane." The late Precambrian rocks of the Bras d'Or "terrane" are also overlain by a volcano-sedimentary sequence of Silurian age (Clyburn Brook formation). These observations suggest that rocks of the Aspy "terrane" lie unconformably on those of the Bras d'Or "terrane." The Eastern Highlands shear zone is therefore not a terrane boundary. The Ordovician–Silurian rocks of the Aspy "terrane" are interpreted to have formed in an arc–back-arc basin system. The back-arc basin is interpreted to have formed by rifting in the Bras d'Or "terrane" and the Eastern Highlands shear zone to have been related to the closure of the basin.

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.

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.

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.

Sign in / Sign up

Export Citation Format

Share Document