1. Earth Sciences Department, University of Toronto, 22 Ursula Franklin St., Toronto, ON M5S 3B1, Canada.
2. Department of Earth and Environmental Science, Acadia University, Wolfville, NS B4P 2R6, Canada.
3. Geoscience and Mines Branch, Nova Scotia Department of Natural Resources and Renewables, P.O. Box 698, Halifax, NS B3J 2T9, Canada.