Rock-water interaction in ash-flow tuffs (Yucca Mountain, Nevada, U.S.A.) - The record from uranium studies

Forty-eight core samples of variably welded, devitrified, fractured and altered ash-flow tuffs from Yucca Mountain, Nye County, Nevada, were selected for comparative analysis by uranium-based methods to estimate past interaction with oxidizing water. Tests for such interaction include: (1) chemical fractionation of U from Th; (2) extent of association of U with secondary alteration products; and (3) isotopic fractionation of U from its long-lived daughters. Results aid the selection of hyrologically isolated host rocks for radioactive waste disposal near the Nevada Test Site. Samples are from the Bullfrog Member, Crater Flat Tuff, and the Topopah Spring Member, Paintbrush Tuff, both of Miocene age. (Auth.)