1. Department of Earth, Environmental, and Planetary Sciences, Brown University, P.O. Box 1846, Providence, Rhode Island 02912, USA
2. Department of Space Sciences, Fernbank Science Center, 156 Heaton Park Drive, Atlanta, Georgia 30307, USA
3. Escuela de Geologia, Universidad Santo Tomás, Avenida Ejército 146, Santiago, Chile
4. Servicio Nacional de Geología y Minería, Avenida Santa María 0104, Santiago, Chile