Natural radionuclide mobility and its inﬂuence on U-Th-Pb dating of secondary minerals from the unsaturated zone at Yucca Mountain, Nevada
Extreme U and Pb isotope variations produced by disequilibrium in decay chains of 238U and 232Th are found in calcite, opal/chalcedony, and Mn-oxides occurring as secondary mineral coatings in the unsaturated zone at Yucca Mountain, Nevada. These very slowly growing minerals (mm my-1) contain excess 206Pb and 208Pb formed from excesses of intermediate daughter isotopes and cannot be used as reliable 206Pb/238U geochronometers. The presence of excess intermediate daughter isotopes does not...[Show more]
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|Source:||Geochimica et Cosmochimica Acta|
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