Calcite Deposits in Fractures at Yucca Mountain, Nevada

by D. T. Vaniman, Los Alamos Natl Lab, Los Alamos, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1993


Calcite is one of the latest-formed minerals within fractures at Yucca Mountain. Petrographic and chemical studies of these calcites have the potential, in conjunction with fluid-inclusion and isotopic studies, of determining the locations of transmissive regions in unsaturated tuffs. Preliminary chemical data for fracture calcites from Yucca Mountain indicate a common composition for most unsaturated-zone calcites (low abundances of transition elements; chondrite-normalized lanthanide-element patterns with prominent negative Ce and Eu anomalies) that is distinct from most calcites in the saturated zone. Exceptions to this general characterization occur in drill core USW G-4; the reasons for these deviations are as yet unknown, but the rich variety of calcite compositions suggests that much information is to be gained from further studies.

Subject Headings: Cracking | Radioactive wastes | Chemical elements | Site investigation | Subsurface investigation | Drilling | Geology | Calcium | Nevada | United States

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