Mineralogical, Chemical, and Isotopic Characterization of Fracture-Coating Minerals in Borehole Samples from Western Pahute Mesa and Oasis Valley, Nevada

Abstract

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Geochemical and Isotopic Evaluation of Groundwater Movement in Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nevada, Rev. No.: 0

“…Therefore, it is also important to consider data for reactive fracture-lining minerals, particularly clay and zeolite minerals. Fracture-mineral characterization studies were conducted on Pahute Mesa core samples to support earlier geochemical investigations (IT, 1998;Benedict et al, 2000). These studies included some quantitative chemical analyses of secondary fracture-lining phases, principally clays and zeolites (clinoptilolite and mordenite).…”

“…Qualitative descriptions of fracture-coating phases reported by IT (1998) and Benedict et al (2000) are as follows: In the TMA, fracture-lining minerals were characterized by calcite + mixed illite/smectite + opaline silica in the unsaturated zone (based on two samples) and calcite + mixed illite/smectite + quartz + feldspars + zeolites + iron (Fe)-and manganese (Mn)-oxyhydroxides in the saturated zone (based on six samples). Fracture-coating phases representing the PBR consisted of Ca-Mg-Fe carbonate minerals + pyrite + chlorite + epidote + mixed illite/smectite + local Fe-oxides.…”

Estimation of Groundwater Recharge at Pahute Mesa using the Chloride Mass-Balance Method

“…Hydrothermal alteration has been observed in boreholes in western Pahute Mesa, Thirsty Canyon, Oasis Valley, Yucca Mountain, and south of Pahute Mesa (e.g. Stoller-Navarro, 2006;Benedict et al, 2000;IT, 1998;Blankennagel and Weir, 1973;Schoff and Moore, 1964) and is likely the source of elevated chloride and sulfate concentrations in western Pahute Mesa.…”

Groundwater Flow Model of Corrective Action Units 101 and 102: Central and Western Pahute Mesa, Nevada Test Site, Nye County, Nevada, Revision 0

“…Such mineralization is well studied for the Yucca Mountain region of the SWNVF (e.g., Levy et al, 1999;Carlos et al, 1995; Appendix B Carlos et al, 1993), and within the Pahute Mesa source region (Benedict et al, 2001). This generally associated hydrothermal alteration, depending on its intensity, can completely fill the permeable portions of faults, converting them to impermeable barriers .…”