1. Center for International Energy and Environmental Policy and the Bureau of Economic Geology, Jackson School of Geosciences; Univ. of Texas at Austin, University Station, Box X, Austin TX 78713–8924 (corresponding author).
2. Environmental Studies Center, Qatar Univ., P.O. Box 2713, Doha, Qatar.
3. Geological Science Dept., Univ. of Texas at El Paso, El-Paso, TX 79968.