Geology topics

John N. Rosholt

Publications and source records attributed to John N. Rosholt.

3 recordsLinked to original sources

USGS1978

Uranium in waters and aquifer rocks at the Nevada Test Site, Nye County, Nevada

Previous chemical, geological, and hydrological information describing the physical and chemical environment of the Nevada Test Site (a Federal reserve for the testing of nuclear explosive devices) has been combined with new radiochemical and isotope data for water and rock samples in order to explain the behavior of uranium during alteration of thick sequences of rhyolitic volcanic rocks and associated volcaniclastic sediments. A model is proposed in which uranium mobility is controlled by two competing processes. Uranium is liberated from the volcanic rocks through dissolution of the glassy constituents and is carried in solution as a uranyl carbonate complex. Uranium is subsequently removed from solution by adsorption on secondary oxides of iron, titanium, and manganese, as observed in fission-track maps of aquifer rocks. The model explains the poor correlation of dissolved uranium with depth within tuffaceous sequences in which percolation of ground water is predominantly downward. Good positive correlation of dissolved uranium with dissolved Na, total dissolved solids, and total carbonate supports the glass dissolution model, while inverse correlation of dissolved uranium with U 234 /U 238 ratios of waters implies uranium is being absorbed by a relatively insoluble, surficial phase. Alpha radioactivity of Test Site water is primarily caused by high U 234 contents, and beta activity is highly correlated with dissolved K (K 40 ). Small amounts of dissolved radium, Pb 210 , and Po 210 are present but no evidence was found for alpha activity sources related to nuclear testing (Pu, U 235 ). A filtered but unacidified carbonate solution of uranium was found to be stable (± 10 percent of original U concentration) for years when stored in acid-washed polyethylene bottles.

Nevada↗

USGS1977

A comparison of some analytical techniques for determining uranium, thorium, and potassium in granitic rocks

Geochemical exploration for uranium requires accurate and precise determinations of low-level concentrations. We have used seven different techniques and four different treatments of the fluorometric method to analyze for uranium in granitic rocks. In addition we have used four analytical techniques for thorium and three analytical techniques for potassium, two elements that are commonly present in anomalous amounts within uranium provinces. Our results show that commonly used techniques for thorium and potassium determinations are both adequately precise and accurate, but that many techniques used for uranium determinations lack the necessary precision or accuracy for complete geochemical prospecting. We suggest that a combination of delayed-neutron determinations for uranium and γ -ray spectrometric analyses for radium equivalent uranium, thorium, and potassium provides the best data base for geochemical exploration for uranium. If more detailed interpretations are desired, the combination of γ -ray spectrometry and α -spectrometry may be best. Carefully done fluorometric analyses should be adequate for water, ore, mineralized rock, and other applications where high precision and accuracy are not required.

Journal of Research of the U.S. Geological Survey↗

USGS1976

Radioactive mineral springs in Delta County, Colorado

The system of springs in Delta County, Colo., contains geochemical clues to the nature and location of buried uranium-mineralized rock. The springs, which occur along the Gunnison River and a principal tributary between Delta and Paonia, are regarded as evidence of a still-functioning hydrothermal system. Associated with the springs are hydrogen sulfide and sulfur dioxide gas seeps, carbon dioxide gas-powered geysers, thick travertine deposits including radioactive travertine, and a flowing warm-water (41?C) radioactive well. Geochemical study of the springs is based on surface observations, on-site water-property measurements, and sampling of water, travertine, soft precipitates, and mud. The spring deposits are mostly carbonates, sulfates, sulfides, and chlorides that locally contain notable amounts of some elements, such as arsenic, barium, lithium, and radium. Samples from five localities have somewhat different trace element assemblages even though they are related to the same hydrothermal system. All the spring waters but one are dominated by sodium chloride or sodium bicarbonate. The exception is an acid sulfate water with a pH of 2.9, which contains high concentrations of aluminum and iron. Most of the detectable radioactivity is due to the presence of radium-226, a uranium daughter product, but at least one spring precipitate contains abundant radium-228, a thorium daughter product. The 5:1 ratio of radium-228 to radium-226 suggests the proximity of a vein-type deposit as a source for the radium. The proposed locus of a thorium-uranium mineral deposit is believed to lie in the vicinity of Paonia, Colo. Exact direction and depth are not determinable from data now available.

Open-File Report↗