Affiliation: | School of Earth and Ocean Sciences, University of Victoria, Victoria, PO Box 3055,;BC, Canada V8W 3P6. E-mail: Department of Earth &Planetary Sciences, McGill University, 3450;University St., Montreal, Quebec, Canada H3A 2A7 Pacific Geoscience Centre, Geological Survey of Canada, 9860;West Saanich Rd., Sidney, BC, Canada V8L 4B2 U.S. Geological Survey, MS 977, 345;Middlefield Road, Menlo Park, CA 94025, USA |