Rb–Sr ages of silicic igneous rocks and deformation, Burlington Peninsula, Newfoundland

• Published in: Canadian Journal of Earth Sciences
• Main Author: Pringle, Ian R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1978
• Subjects: Baie Verte; Newfoundland
• Online Access: http://dx.doi.org/10.1139/e78-030; http://www.nrcresearchpress.com/doi/pdf/10.1139/e78-030

The Burlington Peninsula, east of the Baie Verte Lineament, is underlain by the Eastern Division of the Fleur de Lys Supergroup, a sequence of metasediments and metavolcanic rocks that is intruded by plutonic masses of granitic to granodioritic composition. This sequence has been designated as Cambrian or older and the deformation and metamorphism in the area interpreted as pre-Ordovician. Recently, however, it has been shown that at least part of the succession is post Lower Ordovician and a mid or late Palaeozoic age has been proposed for the major deformation affecting the area.Rb–Sr ages obtained in the present study area are: (a) whole-rock isochrons—Dunamagon Granite, 413 ± 10 Ma; Cape Brulé Porphyry, 393 ± 25 Ma; Cape St. John Group Ignimbrites, 343 ± 15 Ma and 429 ± 50 Ma; Mic Mac Group Ignimbrite, 375 ± 15 Ma; (b) Biotite ages—Dunamagon Granite, 334, 356 and 358 Ma; (c) Mineral isochron—Burlington Granodiorite, 422 ± 40 Ma. Because of extensive trace element migration in at least some of these units, the interpretation of the ages is complex and does not allow a unique history of the area to be determined. However, the ages do support the proposed mid or late Palaeozoic age for the major deformation and indicate that pre-Ordovician orogeny did not prevail on the scale previously envisaged.