1. 1Geological Sciences, Stanford University, Stanford, California 94305, USA
2. 2Department of Geosciences, Princeton University, Princeton, New Jersey 08544, USA
3. 3Department of Geological and Mining Engineering and Sciences, Michigan Technological University, Houghton, Michigan 49931, USA
4. 4Department of Earth Sciences, Dartmouth College, Dartmouth, Massachusetts 03755, USA
5. 5Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, Lafayette, Indiana 47907, USA