USGS Science⌕ Search

Geology topics

John Nicholas Rosholt

Publications and source records attributed to John Nicholas Rosholt.

8 recordsLinked to original sources
USGS1963

Uranium in sediments

An oceanographic approach is used to study the distribution of abnormal occurrences of uranium in sediments. The occurrences predominate in marine phosphorites, black marine shales, and deposits in terrestrial-fluvial sandstones and ancient conglomerites. In early Paleozoic times, marine shales accounted for the majority of uranium deposition. By the beginning of Tertiary time, the balance had shifted to predominant deposition in marine phosphorites which continued to the present. Much smaller total quantities of uranium are associated with terrestrial sandstones and ancient conglomerates, although its concentration is greater and its economic recovery is more feasible. All the abnormal occurrences fit into a unique niche in the hydrologic cycle, and emplacement was largely controlled by cycles of organic substances in water. Radiochemical analyses of Pa 231 , Th 230 , and Ra 226 were made on a few hundred samples from sandstone-type uranium deposits. These results, in comparison to the uranium content of samples, indicate that much of the uranium in terrestrial sediments is presently in a slow, continual state of migration toward the ocean.

Open-File Report↗
USGS1961

Uranium migration and geochemistry of uranium deposits in sandstone above, at, and below the water table; Part 1, Calculation of apparent dates of uranium migration in deposits above and at the water table

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.

Economic Geology↗
USGS1961

Uranium migration and geochemistry of uranium deposits in sandstone above, at, and below the water table; Part 2, Relationship of uranium migration dates, geology, and chemistry of the uranium deposits

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.

Montana, South Dakota, Wyoming↗
USGS1953

A quantitative radiochemical method for the determination of the major sources of natural radioactivity in ores and minerals

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 .

Trace Elements Investigations↗