1. 1Department of Earth Sciences, University of Oxford, 3 South Parks Road, Oxford OX1 3AN, UK
2. 2Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A 0E8, Canada
3. 3Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK
4. 4Museum of Natural History, University of Oxford, Parks Road, Oxford OX1 3PW, UK
5. 5Camborne School of Mines, University of Exeter (Cornwall Campus), Penryn, Cornwall TR10 9EZ, UK
6. 6Wadia Institute of Himalayan Geology, Dehradun 248 001, India