Detailed petrographic descriptions and microprobe data for tertiary silicic volcanic rocks in drill hole USW G-1, Yucca Mountain, Nevada

Abstract

This report contains detailed petrographic descriptions of 74 thin sections from drill hole USW G-l at Yucca Mountain, Nevada.These descriptions are keyed to the distinctions between devitrified, vitrophyre, vitric, and zeolitized intervals below the Topopah Spring Member repository horizon.The petrographic features of the zeolitized intervals down through the Crater Flat tuff, as well as the sorption properties determined from these intervals, suggest that these zeolite occurrences may each have comparable sorptive capability.

Assessment of industrial minerals and rocks in the controlled area

“…Likewise, Caporuscio et al (1985) reported clay mineral analyses for clay minerals below 3,600 feet in drill hole G-1 . Levy (1984) reported clay mineral analyses for a few cuttings samples from drill holes H-4 and H-5, including an analysis for the shallow smectite-rich zone in the Paintbrush Group described above H-5, at 420 feet) that shows it to contain Mg-Ca smectite with less than 0.5% Na.…”

Smectite dehydration and stability: Applications to radioactive waste isolation at Yucca Mountain, Nevada

“…Smectites in Yucca Mountain contain variable amounts of Na, K, and Ca, but few analyses of smectites are available due to the difficulty of analyzing hydrous, fine-grained minerals using the electron microprobe. In general, deeper smectites typically contain subequal amounts of Na, K, and Ca (Bish et al 1981;Levy 1984;Caporuscio et al 1985), with a tendency for increased amounts of Na in shallower smectites and increased K in deeper smectites (Vaniman et al 1984). Smectites that have replaced glass underlying devitrified Topopah Spring Member tuff from drill hole USW H-5 are Ca rich, with very low K and Na contents (Levy 1984).…”