1. Formerly Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, University Station, Box X, Austin, Texas 78713-8924, USA; presently WesternGeco, Schlumberger, 3750 Briarpark Drive, Houston, Texas 77042, USA.(corresponding author).
2. Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, University Station, Box X, Austin, Texas 78713-8924, USA..
3. Formerly Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, University Station, Box X, Austin, Texas 78713-8924, USA; presently School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China..