Isotopic and Trace Element Variability in Altered and Unaltered Tuffs at Yucca Mountain, Nevada

by Z. E. Peterman, U.S. Geological Survey, Denver, United States,
R. W. Spengler, U.S. Geological Survey, Denver, United States,
F. R. Singer, U.S. Geological Survey, Denver, United States,
R. P. Dickerson, U.S. Geological Survey, Denver, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1993


Reference stratigraphic sections near Yucca Mountain, Nevada were established and sampled in outcrop areas where the volcanic rocks have been minimally altered. Isotopic and trace element analyses obtained for these reference sections are baseline data for assessing the degree and extent of element mobility attendant with past zonal alteration of the rock mass. In agreement with earlier studies, zeolitization is shown to have occurred under wholesale open-system conditions. Calcium was increased by two three times the baseline values and strontium up to twenty times. In contrast, barium displays less variability, and the high-field strength elements zirconium and titanium were the least mobile during zeolitization. The data reported here establish the usefulness of reference sections of assessing past elements mobility. The information gained will be helpful in predicting possible future element mobility induced by thermally activated fluids in the near field of a potential repository.

Subject Headings: Trace elements | Radioactive wastes | Geology | Rocks | Fluid flow | Volcanic deposits | Data analysis | Rock masses | Nevada | United States

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