1. Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
2. Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada.
3. Department of Geology and Geophysics, University of Wisconsin, Madison, WI 53706, USA.
4. Department of Geology and Geochemistry, Stockholm University, SE-10691, Stockholm, Sweden.
5. Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA.
6. U.S. Geological Survey, Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
7. School of Environmental Science, University of Ulster, Coleraine, County Londonderry, BT52 1SA, UK.