THE ROLE OF INFILTRATION WATERS IN THE FORMATION OF SECONDARY MINERALS IN THE VADOSE ZONE OF YUCCA MOUNTAIN (Nevada, USA): A THERMODYNAMIC ANALYSIS
G.A. Pal'yanova, S.Z. Smirnov, and Yu.V. Dublyansky
Institute of Mineralogy and Petrography, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
Keywords: Thermodynamic modeling, water-rhyolite interaction, Yucca Mountain, secondary mineralization, nuclear waste repository
Pages: 722-738
Abstract
Many fractures and lithophysae in rhyolite tuffs making up Yucca Mountain in Southern Nevada, USA, are lined with epigenetic minerals (calcite, quartz, chalcedony, opal, fluorite, zeolites, and strontianite) indicative of the migration of mineralized waters within the mountain vadose zone in the geologic past. To evaluate the possibility of formation of these minerals as a result of meteoric water-rhyolite interaction, we performed a thermodynamic modeling of the system rhyolite-carbonate-aqueous solution-gas (CO2, O2) open to oxygen (pO2 = 0.2 bar) and carbon dioxide (pCO2 = 0.0003 bar). The compositions of produced ground waters and equilibrated mineral associations were calculated using the
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