1. École Polytechnique de Montréal, P.O. Box 6079, Centre-Ville Station, Montréal, Québec H3C 3A7, Canada.
2. Present address: Monash University, School of Geosciences, Building 28, Clayton Campus, Wellington Road, Melbourne, Vic. 3800, Australia.
3. Corresponding author.
4. Université du Québec en Abitibi-Témiscamingue, 445 boul. de l’Université, Rouyn-Noranda, Québec J9X 5E4, Canada.