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At least 37 records · Page 2Linked to original sources
USGS1985

Lacustrine-humate model for primary uranium ore deposits, Grants uranium region, New Mexico

Two generations of uranium ore, primary and redistributed, occur in fluvial sandstones of the Upper Jurassic Morrison Formation in the San Juan basin; the two stages of ore formation can be related to the hydrologic history of the basin. Primary ore formed soon after Morrison deposition, in the Late Jurassic to Early Cretaceous, and a model, the lacustrine-humate model, is offered that views primary mineralization as a diagenetic event related to early pore fluid evolution. The basic premise is that the humate, a pore-filling organic material closely associated with primary ore, originated as humic acids dissolved in pore waters of greenish-gray lacustrine mudstones deposited in the mud-flat facies of the Brushy Basin Member and similar "K" shale beds in the Westwater Can on Member. During compaction associated with early burial, formation water expelled from lacustrine mudstone units carried these humic acids into adjacent sandstone beds where the organics precipitated, forming the humate deposits that concentrated uranium. During the Tertiary, much later in the hydrologic history of the basin, when Jurassic sediments were largely compacted, oxygenated ground water flowed basinward from uplifted basin margins. This invasion of Morrison sandstone beds by oxidizing ground waters redistributed uranium from primary ores along redox boundaries, forming ore deposits that resemble roll-front-type uranium ores.

New Mexico↗
USGS1991

Maps showing the distribution of uranium-deposit clusters in the Colorado Plateau uranium province

The Colorado Palteau Uranium Province (CPUP) is defined by the distribution of uranium deposits, chiefly the sandstone-type, in upper Paleozoic and Mesozoic sedimentary rocks within the Colorado Plateau physiographic province (Granger and others, 1986). The uranium province is bordered by widely distributed and mostly minor uranium deposits in Precambrian and Tertiary rocks and by outcrops of Tertiary extrusive and intrusive igneous rocks.

Colorado Plateau↗
USGS1982

Uranium-lead isochron age and preliminary sulfur isotope systematics of the Felder uranium deposit, south Texas

Uranium-lead isotope systematics of roll-front ores in Miocene sandstone at the Felder and McLean uranium deposits (south Texas coastal plain) give a well-defined 207 Pb/ 204 Pb- 235 U/ 204 Pb isochron age of 5.07 + or - 0.15 m.y. The relatively slight degree of scatter of the points defining the isochron is probably due to initial Pb isotope inhomogeneity, and the resulting inferred persistence of closed system behavior for U and Pb is probably the result of the long-term presence of U- and Pb-immobilizing H 2 S. 206 Pb/ 238 U systematics are badly scattered owing to long-term migration of radioactive daughters of 238 U. Beta- and gamma-activity systematics of the ores consistently identify those with grossly anomalous Pb isotope systematics, however, and proved highly useful in identifying ores that have gained gross amounts of uranium daughters.FeS 2 minerals in the altered tongue of the host sandstone are characterized by abundant postore pyrite and heavy delta 34 S values, whereas FeS 2 minerals in mineralized and unaltered, barren rock are characterized by abundant ore-stage marcasite and by light delta 34 S values. The delta 34 S values of FeS 2 minerals in the altered tongue are similar to those defined for sour gas from the underlying Edwards Limestone of Cretaceous age, indicating the probable source for the sulfur of an inferred resulfidization event. The 5.07-m.y. isochron age probably reflects the end of roll-front development; we believe that the end was due to the resulfidization and does not preclude significant earlier periods of mineralization. Modern ground water in the area is also sulfide bearing (thus helping preserve the deposit), but with delta 34 S values distinct from those of sulfides in the resulfidized zone of the host rock.

Texas↗
USGS1983

Comparison of the chemical characteristics of the uranium deposits of the Morrison Formation in the Grants uranium region, New Mexico

Statistical treatment of the chemical data of samples from the northeast Church Rock area, Ruby deposit, Mariano Lake deposit, and the Ambrosia Lake district indicates that primary ore-forming processes concentrated copper, iron, magnesium, manganese, molybdenum, selenium, vanadium, yttrium, arsenic, organic carbon, and sulfur, along with uranium. A barium halo that is associated with all of these deposits formed from secondary processes. Calcium and strontium were also enriched in the ores by secondary processes. Comparison of the chemical characteristics of the redistributed deposits in the Church Rock district to the primary deposits in the Grants uranium region indicates that calcium, manganese, strontium, yttrium, copper, iron, magnesium, molybdenum, lead, selenium, and vanadium are separated from uranium during redistribution of the deposits in the Church Rock area. Comparisons of the chemical characteristics of the Church Rock deposits and the secondary deposits at Ambrosia Lake suggest some differences in the processes that were involved in the genesis of the redistributed deposits in these two areas.

Open-File Report↗
USGS1952

Compilation of data on the uranium and equivalent uranium content of samples analyzed by U.S. Geological Survey during a program of sampling mine, mill, and smelter products

In 1942 the Geological Survey began to collect, in response to a request made by the War Production Board, samples of mine, mill, and smelter products. About 1,400 such samples were collected and analyzed spectrographically for about 20 elements that were of strategic importance, in order to determine whether any of the products analyzed might be possible sources of some of the needed elements. When attention was directed to radioactive elements in 1943, most of the samples were scanned for radioactivity. Part of the work was done on behalf of the Division of Raw Materials of the Atomic Energy Commission. The sources, mine mill, smelter, or prospect, from which these samples were collected, the kind of material sampled, i.e. ores, concentrates, middlings, tailings, flue dusts, and so forth, and the radioactivity of the samples are listed in this report. Samples of the materials collected in the course of the Geological Survey’s investigations for uranium are excluded, but about 500 such samples were analyzed spectrographically for some or all of the same 20 elements sought in the samples that are the subject of this report. Most of the samples were tested only for their radioactivity, but a few were analyzed chemically for uranium. The radioactivity of many of the samples tested in the early screening was determined only qualitatively. Several samples were tested at one time, and if the count obtained did not exceed a predetermined minimum above background, the samples were not tested individually. If the count was more than this minimum, the samples were tested individually to identify the radioactive sample or samples and to obtain a quantitative value for the radioactivity. In general, the rough screening served as a basis for separating samples in which the radioactivity amount to less than 0.003 percent equivalent uranium from those in which it exceeded that amount. Some aspects of various phases of the investigation of radioactivity in these samples have been reported in various other reports, as follows.

Trace Elements Investigations↗
USGS1981

Geologic controls of uranium mineralization in the Tallahassee Creek uranium district, Fremont County, Colorado.

Two important orebodies have been defined by drilling in the Tallahassee Creek uranium district, Fremont County, Colorado, namely the Hansen and the Picnic Tree. Host rocks are respectively the upper Eocene Echo park Alluvium, and the lower Oligocene Tallahassee Creek Conglomerate. Average ore grade is about 0.08% U3O8. The principal source rock is the lower Oligocene Wall Mountain Tuff. Leaching and transportation of the uranium occurred in alkaline oxidizing ground water that developed during alteration of the ash in a semi-arid environment. The uranium was transported in the groundwater and deposited in a reducing environment controlled by carbonaceous material and associated pyrite. Localization of the ore was controlled by groundwater flow conditions and by the distribution of organic matter in the host rock. -from Author

Mountain Geologist↗
USGS1985

The Schwartzwalder uranium deposit, II: Age of uranium mineralization and lead isotope constraints on genesis

U-Pb isotope analyses of ores from the Schwartzwalder uranium mine, Colorado, show that these ores have high amounts of initial (common) Pb and that the initial Pb was both variable and relatively radiogenic in its Pb isotope ratios ( 206 Pb/ 204 Pb = 26-30). As a result, the only useful approach to dating these ores is with U-Pb isochrons, and even so, some means of dealing with the variable initial Pb isotope ratios is required. Because the common Pb in these ores was apparently derived from sources of similar age and Th/U, the observed 208 Pb/ 204 Pb of these Th-free ores can be used either to identify sample suites with similar initial Pb isotope ratios or to normalize for the variable initial Pb isotope ratios. The resulting U-Pb isochrons indicate an age of mineralization for both Illinois vein and Titan vein ores of 69.3 + or - 1.1 m.y., suggesting that the deposit was formed during the earliest stages of Laramide uplift and under at least 3 km of Phanerozoic cover. The initial Pb isotope systematics of the ores show that the metals in the Schwartzwalder ores were derived from source(s) of 1,730 + or - 130-m.y.-age, with a Th/U of 2.2 + or - 0.2 and 238 U/ 204 Pb of 30 to 60. These restrictions on the source(s) of the metals rule out the possibility that the deposit could have been formed by remobilization of a Proterozoic uranium deposit, and both the 69.3-m.y.-age of the ores and their initial Pb isotope ratios preclude any contribution of metals to the deposit by younger volcanics such as those in the Denver Formation.

Economic Geology↗
USGS1978

Geology of the uranium prospect at Camp Smith, New York, with a new model for the formation of uranium deposits in metamorphosed submarine volcanogenic rocks

Uraninite of Precambrian age occurs locally in and around a massive sulfide deposit at Camp Smith, Westchester and Putnam Counties, New York. The host rocks are believed to be part of a sequence of marine sediments and submarine volcanogenic rocks that were metamorphosed to leucogneisses, amphibolites, and amphoholite gneisses in the granulite facies. Ore grade concentrations of uraninite occur (1) in the outer Cu-Ni-bearing zone of the sulfide body; (2) in magnetite-rich and scapolite-rich layers within amphibolite gneiss; and (3) in amphibole-quartz-feldspar + pyroxene pegmatites. The uranium-rich horizons are generally near the contact between rocks of keratophyre and spilite affinities. It is suggested that the iron oxide, uranium-rich, and sulfide-rich horizons and their host rocks were originally deposited in the distal, volcanogenic, massive sulfide environment.

New York↗
USGS1977

Uranium and coexisting element behaviour in surface waters and associated sediments with varied sampling techniques used for uranium exploration

Optimum sampling methods in surface water and associated sediments for use in uranium exploration are being studied at thirty sites in Colorado, New Mexico, Arizona and Utah. For water samples, filtering is recommended to increase sample homogeneity and reproducibility because for most elements studied water samples which were allowed to remain unfiltered until time of analysis contained higher concentrations than field-filtered samples of the same waters. Acidification of unfiltered samples resulted in still higher concentrations. This is predominantly because of leaching of the elements from the suspended fraction. U in water correlates directly with Ca, Mg, Na, K, Ba, B, Li and As. In stream sediments, U and other trace elements are concentrated in the finer size fractions. Accordingly, in prospecting, grain size fractions less than 90 μm (170 mesh) should be analyzed for U. A greater number of elements (21) show a significant positive correlation with U in stream sediments than in water. Results have revealed that anomalous concentrations of U found in water may not be detected in associated sediments and vice versa. Hence, sampling of both surface water and coexisting sediment is strongly recommended.

Journal of Geochemical Exploration↗
USGS1986

Uranium series disequilibrium in a young surficial uranium deposit, northeastern Washington, U.S.A.

A recently discovered ore-grade accumulation of U in organic-rich sediments of late Quaternary age provides an opportunity for studying the early association of U, U-daughters, and organic matter in a natural setting. The U occurs in valley-fill sediments of peat, peaty clay, silt, and sand along the north fork of Flodelle Creek, Stevens County, Washington. Radiometric techniques (delayed neutron, high-resolution gamma-ray spectrometry, thin-source alpha spectrometry) were employed to determine the abundance and distribution of U-series nuclides, the extent of secular equilibrium within the U decay series, and the apparent U-series ages of U incorporation. Sixteen lithologically distinct intervals were sampled from a 292 cm core. Uranium contents range from 140 to 2790 ppm and are positively correlated with organic contents. Measured alpha activity ratios of 234 U/ 238 U (1.31–1.38) are very similar to those reported in coexisting waters, suggesting a rather constant isotopic composition of introduced U. Much lower Th contents of <10–40 ppm are controlled by the type and abundance of silicate detritus. The youth of the host sediments (<15 000 a) and the paucity of associated radioactivity suggested large excesses of U relative to radioactive daughters and such excesses were observed, particularly in the shallowest intervals. Apparent ages of U emplacement determined by the (alpha) activity ratio of 230 Th daughter to 234 U parent show a general increase with depth and fair agreement with estimated depositional ages. This observation suggests dominantly syndepositional or early post depositional emplacement of U followed by decay-generated buildup of 230 Th daughter with time. However, interval by interval comparisons of the relative abundances of other daughters, particularly 226 Ra and 210 Pb, indicate variability caused by processes other than closed-system growth and decay, probably because chemically diverse daughters that are decay-generated in situ have differing mobilities and because upwelling ground water continuously adds more U and minor amounts of daughters. If 230 Th is considered the least susceptible to these modifications, the data suggest some addition of 234 U in the deepest intervals and some loss of 226 Ra and/or gain of 222 Rn throughout the studied core.

Washington↗