Compilation of radiometric age and trace-element geochemical data, Yucca Mountain and surrounding areas of southwestern Nevada

Abstract

This document is a compilation of available radiometric age and trace-element geochemical data for volcanic rocks and episodes of hydrothermal activity in Yucca Mountain and the surrounding region of southwestern Nevada. Only the age determinations considered to be geologically reasonable (consistent with stratigraphic relations) are listed below. A number of the potassium-argon (K-Ar) ages of volcanic rocks given by Kistler, Marvin et al., Noble et al., Weiss et al., and Noble et al. are not included as these ages have been shown to be incorrect or disturbed by hydrothermal alteration based on subsequent stratigraphic and/or petrographic data and the recognition of errors in K-Ar age determinations related to incomplete extraction of argon. In cases where absolute ages are tightly constrained by high precision {sup 40}Ar/{sup 39}Ar ages and unequivocal stratigraphic relations, we have omitted the less precise K-Ar age data. Similarly, the more precise single-crystal laser-fusion {sup 40}Ar/{sup 39}Ar age determinations of certain units are reported and less precise ages by multi-grain bulk-fusion {sup 40}Ar/{sup 39}Ar methods are not included. This compilation does not include age data for basaltic rocks of Pliocene and Quaternary age in the Yucca Mountain region.