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Impact of quaternary climate on seepage at Yucca Mountain, Nevada

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Abstract

Uranium-series ages, oxygen-isotopic compositions, and uranium contents were determined in outer growth layers of opal and calcitefrom 0.5- to 3-centimeter-thick mineral coatings hosted by lithophysal cavities in the unsaturated zone at Yucca Mountain, Nevada, the proposed site of a permanent repository for high-level radioactive waste. Micrometer-scale growth layering in the minerals was imaged using a cathodoluminescence detector on a scanning electron microscope. Determinations of the chemistry, ages, and delta oxygen-18 (??18O) values of the growth layers were conducted by electron microprobe analysis and secondary ion mass spectrometry techniques at spatial resolutions of 2 to about 20 micrometers (??m) and 25 to 40 ??m, respectively. Growth rates for the last 300 thousand years (k.y.) calculated from about 300 new high-resolution uranium-series ages range from approximately 0.5 to 1.5 ??m/k.y. for 1- to 3-centimeter-thick coatings, whereas coatings less than about 1-centimeter-thick have growth rates less than 0.5 ??m/k.y. At the depth of the proposed repository, correlations of uranium concentration and ??18O values with regional climate records indicate that unsaturated zone percolation and seepage water chemistries have responded to changes in climate during the last several hundred thousand years.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Title:
Impact of quaternary climate on seepage at Yucca Mountain, Nevada
ISBN:
0894486918; 9780894486913
Volume
2006
Year Published:
2006
Language:
English
Larger Work Title:
Proceedings of the 11th International High Level Radioactive Waste Management Conference, IHLRWM
First page:
199
Last page:
206
Number of Pages:
8
Conference Title:
11th International High Level Radioactive Waste Management Conference
Conference Location:
Las Vegas, NV
Conference Date:
30 April 2006 through 4 May 2006