Age constraints on fluid inclusions in calcite at Yucca Mountain

Conference · Sun Apr 29 04:00:00 EDT 2001

OSTI ID:794113

Neymark, Leonid A ^[1]; Amelin, Yuri V; Paces, James B; Peterman, Zell E; Whelan, Joseph F

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1. USGS, Denver, CO

The {sup 207}Pb/{sup 235}U ages for 14 subsamples of opal or chalcedony layers younger than calcite formed at elevated temperature range between 1.88 {+-} 0.05 and 9.7 {+-} 1.5 Ma with most values older than 6-8 Ma. These data indicate that fluids with elevated temperatures have not been present in the unsaturated zone at Yucca Mountain since about 1.9 Ma and most likely since 6-8 Ma. Discordant U-Pb isotope data for chalcedony subsamples representing the massive silica stage in the formation of the coatings are interpreted using a model of the diffusive loss of U decay products. The model gives an age estimate for the time of chalcedony formation around 10-11 Ma, which overlaps ages of clay minerals formed in tuffs below the water table at Yucca Mountain during the Timber Mountain thermal event.

• Research Organization: U.S. Geological Survey, Denver, CO (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AI08-97NV12033
• OSTI ID: 794113
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AGE-CONSTRAINTS
CALCITE
CLAYS
FLUID INCLUSIONS
HIGH-LEVEL RADIOACTIVE WASTES
INCLUSIONS
ISOTOPE DATING
ISOTOPE RATIO
LEAD 207
MINERALOGY
RADIOACTIVE WASTE FACILITIES
SILICA
SITE CHARACTERIZATION
URANIUM 235
WATER TABLES
YUCCA MOUNTAIN