Mesoproterozoic and Paleoproterozoic crustal growth in the eastern Grenville Province: Nd isotope evidence from the Long Range inlier of the Appalachian orogen
Published:January 01, 2004
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Alan P. Dickin, 2004. "Mesoproterozoic and Paleoproterozoic crustal growth in the eastern Grenville Province: Nd isotope evidence from the Long Range inlier of the Appalachian orogen", Proterozoic Tectonic Evolution of the Grenville Orogen in North America, Richard P. Tollo, James McLelland, Louise Corriveau, Mervin J. Bartholomew
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New Nd isotope data are presented for plutonic orthogneisses of the Long Range inlier in western Newfoundland. The inlier represents a fragment of Grenvillian basement located within the Appalachian orogenic belt of eastern Canada. The Nd data suggest that the Long Range is divided into two blocks with different crustal formation ages of ca. 1.75 Ga and 1.55 Ga, interpreted as juvenile arc terranes that were accreted to the Laurentian continent during its Proterozoic evolution. The two blocks are correlated with the Paleoproterozoic and Mesoproterozoic terranes of Labradoria and Quebecia previously recognized in the Grenville Province of the mainland. The younger block in the Long Range is also correlated with the Mesoproterozoic gneisses of the Blair River inlier of Cape Breton Island (Nova Scotia), which has a similar crustal formation age of ca. 1.55 Ga. The two blocks are separated by a boundary that cuts across the Long Range mountains and is correlated with a similar boundary on the mainland, west of Sept Iles. Based upon the sharpness of this boundary, it may be a collisional suture between accreted oceanic arc terranes. Based on published dates for substantial 1.5 Ga plutonism immediately southeast of the Wakeham Group, it is suggested that the terrane boundary probably passes fairly near the north shore of the St. Lawrence River at this point, causing the Labradorian crust in this area to be extensively reworked during the accretion of Quebecia to Labradoria.