http://worldcat.org/entity/work/id/2517286970

Summary of Potassium

The purpose of this open-file report is to tabulate the results of the potassium/argon dating program which has been supported by the US Department of Energy during Fiscal Year 1982. During this period dating was done for state teams being supported by the State Low Temperature Resource Assessment Program, for the case study of the Beowawe KGRA being conducted here at Earth Science Laboratory, and for the Mineral Mountains intrusive complex study. During FY-82 about 40 samples were dated. Ten calibration runs and discrimination checks were also completed in order to maintain the laboratory in an operational status. Procedures used for dating remain as in the past. These have been reported previously in Evans (1980), Evans and Brown (1980) and Evans and Brown (1981). They have slightly modified the procedure for treating whole-rock samples by crushing samples to -20, +30 mesh and then leaching the samples in 10% nitric acid and then 10% hydrofluoric acid to remove any easily soluble weathering products. This seems to enhance results on young whole-rock basalt samples by reducing atmospheric argon contents and thereby improving precision of the dates.

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