[1] Purdue Univ, Dept Earth Atmospher & Planetary Sci, W Lafayette, IN 47907 USA
[2] New Mexico Inst Min & Technol, Dept Earth & Environm Sci, Socorro, NM 87801 USA
[3] New Mexico Inst Min & Technol, New Mexico Bur Geol & Mineral Resources, Socorro, NM 87801 USA
[4] Los Alamos Natl Lab, Div Earth & Environm Sci, EES 14, Los Alamos, NM 87545 USA