Geology topics
Publications and source records attributed to John Nicholas Rosholt.
No abstract available.
The migration of U may be studied by the distribution of the radioactive daughter products, which serve as natural tracers in the migration of U. The distribution of the daughter products is determined by radiochemical analyses of samples from ore deposits in sandstone, and the apparent minimum and maximum dates of U introduction or redistribution may be calculated from the Pa 231 /Th 230 ratio. The primary assumption required is that the Pa and Th do not migrate in measurable quantities from the place where they were produced by the decay of the parent U isotopes. The upper limit of age determination is about 250,000 years, based on the half-lives of Pa 231 and Th 230 . The difference in the half-lives of these isotopes is reflected in their differential rates of growth and decay corresponding to migrations of the parent U during the time range considered. The growth and decay patterns, analyzed mathematically, are used to determine the apparent date of U migration. Calculations based on analyses of samples from the Hulett Creek area, Wyoming, illustrate the results for typical sandstone ore deposits that are above and at the water table.
The time of U migration in deposits in sandstone can be determined by correlating apparent age calculations, based on radiochemical analyses, with the geology of a particular deposit. Data were obtained from U ore samples representing deposits above the water table, deposits just above and below perched water tables, and deposits at least 250 ft. below the water table in the Hulett Creek area, Wyoming. The first U deposition occurred more than 250,000 years ago for the deposits now at or above the water table. Approximately 60,000 to 80,000 years ago these deposits were oxidized, leached, and locally enriched. Accumulation of U in the deposits below the water table probably did not start before 180,000 years ago and has continued to the present.
The determination of Th 232 , Rn 222 , and Pb 210 by isolation and subsequent activity analysis of some of their short-lived daughter products is described. The sulfides of bismuth and polonium are precipitated out of solutions of thorium or uranium ores, and the alpha particle activity of PO 214 . PO 212 and PO 210 is determined by scintillation counting techniques. PO 214 activity is used to determine Rn 222 , PO 212 activity for Th 232 , and PO 210 for Pb 210 .