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TitleTectonic setting and regional significance of the 'Port aux Basques Gneiss', SW Newfoundland
AuthorSchofield, D I; van Staal, C RORCID logo; Winchester, J A
SourceJournal of the Geological Society vol. 155, 1998 p. 323-334,
LinksOnline - En ligne
Alt SeriesGeological Survey of Canada, Contribution Series 1997068
PublisherGeological Society of London
Mediapaper; on-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
NTS11O/10NE; 11O/10NW; 11O/11NE
AreaPort au Basques
Lat/Long WENS -59.6667 -58.5000 47.7500 47.5833
Subjectstectonics; general geology; igneous and metamorphic petrology; geochemistry; gneisses; orthogneisses; metabasites; paragneisses; schists; Port Aux Basques Gneiss; Grand Bay Complex; Port Aux Basques Complex; Harbour le Cou Group; Big Barachois Assemblage; Isle Aux Morts Fault Zone; Margaree Orthogneiss; Kelby Cove Orthogneiss; Ordovician; Silurian
Illustrationsgraphs; tables; cross-sections
Released1998 03 01
AbstractThe 'Port aux Basques Gneiss' of southwest Newfoundland comprises three paragneiss and schist assemblages: the Grand Bay and Port aux Basques complexes, and the Harbour le Cou Group. They are intruded by large volumes of basic sheets and coeval Middle Ordovician granitoids: the Margaree and Kelby Cove orthogneiss, which also cut a tectonic slice of earlier ultrabasic to basic rocks within the Grand Bay Complex: the Big Barachois assemblage. The Grand Bay and Port aux Basques complexes are juxtaposed by the Late Silurian Isle aux Morts Fault Zone against the Harbour le Cou Group to the east, which dominantly comprises sillimanite and garnet-bearing, pyritiferous metasediments with amphibolitic intrusions and meta-pillow basalts in its lower stratigraphic units. Geochemical studies have shown that metabasites of the Grand Bay Complex, Port aux Basques Complex, Margaree and Kelby Cove orthogneiss comprise Fractionated and crustally contaminated MORE-like and within plate tholeiites, suggestive of an ensialic Okinawa type back-are basin. These have comparable characteristics to metabasites in the Harbour ie Con Group and suggest that these units comprise remnants of an extensive Mid-Ordovician marginal basin developed within a promontory on the peri-Gondwanan continental margin. In contrast, the Big Barachois assemblage in part comprises a distinct suite of pre-Mid-Ordovician Island Are Tholeiites.

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