Traces of epigenetic hydrothermal activity at Yucca Mountain, Nevada: preliminary data on the fluid inclusion and stable isotope evidence

Samples of opal–quartz–calcite crusts from the 7.8-km-long tunnel excavated under Yucca Mountain were studied to determine their origin. Calcite in these crusts commonly forms relatively large (up to 1.5 cm), euhedral crystal terminations. In some crusts, layers of chalcedony and patches of opal alternate with calcite layers. Chalcedony commonly grades into euhedral quartz crystals. Quartz also forms microdruses of individual crystals up to 8 …