Assessing the natural performance of felsic tuffs using the Rb-Sr and Sm-Nd systems-A study of the altered zone in the Topopah Spring Member, Paintbrush Tuff, Yucca Mountain, Nevada - Peterman, Zell; Spengler, Richard W.; Futa, Kiyoto; Marshall, Brian (Materials Research Society Symposium - Proceedings, 1990)