Regional metamorphism of the Appalachian Humber zone of Gaspé Peninsula: 40 Ar/ 39 Ar evidence for crustal thickening during the Taconian orogeny

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Pincivy, Alix, Malo, Michel, Ruffet, Gilles, Tremblay, Alain, Sacks, Paul E
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2003
• Subjects: Newfoundland
• Online Access: http://dx.doi.org/10.1139/e02-076; http://www.nrcresearchpress.com/doi/pdf/10.1139/e02-076

Geochronological studies on the timing of deformation and metamorphism along the Laurentian margin have shown that the ages of metamorphic events change along-strike within the Newfoundland – southern Quebec segment of the Canadian Appalachians. The Gaspé Peninsula is located at mid-point of the two extremities of this segment. New single-grain laser 40 Ar/ 39 Ar plateau ages solely reflect latest Middle–Late Ordovician metamorphism. Samples taken within the internal Humber zone in the Shickshock Group rocks yield 40 Ar/ 39 Ar muscovite and hornblende ages ranging from 457 to 454 Ma. Samples from the Amphibolite du Diable, the metamorphic sole of the Mont Albert ophiolite, yield 40 Ar/ 39 Ar muscovite and hornblende ages ranging from 459 to 457 Ma. Ordovician ages of the internal Humber zone are consistent with 40 Ar/ 39 Ar ages from southern Quebec and are interpreted as the result of the emplacement onto the margin of both the ophiolite and its metamorphic sole.