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

Geological correlations between Cape Breton Island and Newfoundland are app arent both in surface geology and at deeper crustal levels, based on simila rities 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 Cambria n rocks directly comparable to those in the western part of the Newfoundlan d Avalon terrane. The Bras d'Or terrane is also mainly of Neoproterozoic ag e, but shows lithological and isotopic contrasts with the Mira terrane, Sma ll 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-Gondwana n terrane where rocks of the Gander terrane were later formed. Hence this a rea is part of the Central Mobile Belt and distinct from Avalon terrane sen su stricto. The Aspy terrane is a complex area that may include fragments o f Bras d'Or crust and components of the Gander, Exploits, and possibly Notr e Dame terranes of Newfoundland. It formed by subduction and back-are 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 Grenvil lian inliers in the Humber zone of western Newfoundland in terms of age, ro ck types, and isotopic composition. Silurian and Devonian promontory-promon tory 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 terrane s seems distinct from that under Avalon terrane sensu stricto, it is prefer able to use the term peri-Gondwanan rather than Avalonian to refer to these areas.