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USGS1954

Chatanooga shale investigations along the Sequatchie anticline of Tennessee and Alabama

In 1953 the Chattanooga shale in the Sequatchie anticline was tested for its uranium content by seven diamond drill cores. Concurrent with the drilling, geologic field work was done to determine the distribution, thickness, and structural setting of the shale. The results of this investigation indicate that the Chattanooga shale in the Sequatchie Valley has a higher uranium content than the shale along the Eastern Highland Rim but is more folded and faulted. For the purposes of these investigations the anticline is roughly divisible into three subequal parts, designated as northern, central, and southern. In the northern part the Gassaway member of the Chattanoooga shale is 13 to 21 feet thick and probably contains from 0.0060 to 0.0076 percent uranium. An unusual thickness of the phosphatic interval in one core suggests some duplication of strata. Similar deformation could cause erratic distirbution of the more uraniferous beds. In the central part of the anticline the Dowelltown member of the shale is overlapped by the Gassaway member so that only the latter is present in the central and southern parts of the anticline. The Gassaway is thin and poorly exposed between the State line and Guntersville, Ala., but southward it thickens again to about 40 feet near Blountsville. In the southern part the uranium content of the shale, as determined from three drill cores, is surprisingly low when compared with analyses of 1952 outcrop samples from three sides of the area. On the basis of available data, 20 feet of shale in the area between hole AL-66, 3 miles southwest of Blountsville, and locality 4G-1 at Blount Springs may contain between 0.0057 and 0.0070 percent uranium, but more drilling would have to be done to check the higher figure, which is based on outcrop samples. Data are too sparse to permit reliable estimates of grade and tonnage. More geologic work and drilling are needed to block out the most favorable areas.

Alabama;Georgia;Tennessee↗

USGS1953

Reconnaissance for radioactive deposits in the Nixon Fork mining district, Medfra Quadrangle, central Alaska, 1949

Reconnaissance for radioactive deposits in the Nixon Fork mining district, Medfra quadrangle, central Alaska, in 1949 disclosed the occurrence of allanite in sampled containing as much as 0.05 percent equivalent uranium from the dump of the Whalen mine; the presence of radioactive parisite (a rare-earth fluocarbonate) in a highly altered limestone containing about 0.025 percent equivalent uranium near the Whalen shaft; and radioactive idocrase in samples of altered garnet rock with about 0.025 percent equivalent uranium, form the Crystal shaft of the Nixon Fork mine. This radioactivity is due mostly to thorium rather than uranium. Placer concentrates from Ruby and Eagle Creeks contain 0.078 and 0.26 percent equivalent uranium respectively, in which the radioactivity is due chiefly to uraniferous thorianite. The bedrock source of the uraniferous thorianite was not located primarily because much of the area is overlain by a relatively thick mantle of vegetation (mostly moss) which limited the effectiveness of radiometric surveying. The uraniferous thorianite is believed to occur in a restricted zone or zones at or near the contact of limestone with monzonite similar to the gold-copper ores of the district and the deposits of radioactive parisite and garnet rock at the Whelan and Crystal shafts respectively.

Alaska↗

USGS1985

PROGRESS REPORT ON GEOLOGIC STUDIES OF THE RANGER OREBODIES, NORTHERN TERRITORY, AUSTRALIA.

The Ranger No. 1 and No. 3 orebodies contain about 124,000 tonnes U//3O//8 in highly chloritized metasediments of the lower Proterozoic Cahill Formation within about 500 m of the projected sub-Kombolgie Formation unconformity. In both orebodies, oxidized and reduced uranium minerals occur chiefly in quartzose schists that have highly variable amounts of muscovite, sericite, and chlorite. The effects of several periods of alteration are pervasive in the vicinity of orebodies where biotite and garnet are altered to chlorite, and feldspars to white mica or chlorite. Oxidized uranium minerals, associated with earthy iron oxides, occur from the surface to a depth of about 60 m. Below the oxidized zone, uranium occurs chiefly as uraninite and pitchblende disseminated through thick sections of quartz-chlorite-muscovite schist and has no apparent association with graphite or sulphides. The geologic age(s) of uranium emplacement are obscure because there are few age criteria. Reduced uranium minerals are younger than 1. 8-b. y. -old granite dykes, and some occur locally in 1. 65-b. y. -old Kombolgie Formation.

Conference Paper↗

USGS1978

Radioactive disequilibrium in altered mid-oceanic basalts

A young (<1 m.y.) tholeiitic basalt dredged from the Mid-Atlantic Ridge displays a 234 U excess and a 230 Th deficiency that have resulted from the addition of seawater uranium during weathering at seafloor temperatures. Two older samples, though they acquired substantial amounts of uranium from seawater, are depleted in 234 U, indicating preferential leaching of this isotope. Hydrothermally altered samples suggest that some uranium loss may have occurred. Possible isotopic effects of preferential 234 U leaching, however, are obscured by secondary addition of seawater uranium at lower temperatures.

Earth and Planetary Science Letters↗

USGS1983

Fission track dating of kimberlitic zircons

The only reliable method for dating kimberlites at present is the lengthy and specialized hydrothermal procedure that extracts 206 Pb and 238 U from low-uranium zircons. This paper describes a second successful method by fission track dating of large single-crystal zircons, 1.0–1.5 cm in dimension. The use of large crystals overcomes the limitations imposed in conventional fission track analysis which utilizes crushed fragments. Low track densities, optical track dispersion, and the random orientation of polished surfaces in the etch and irradiation cycle are effectively overcome. Fission track ages of zircons from five African kimberlites are reported, from the Kimberley Pool (90.3 ± 6.5 m.y.), Orapa (87.4 ± 5.7 and 92.4 ± 6.1 m.y.), Nzega (51.1 ± 3.8 m.y.), Koffiefontein (90.0 ± 8.2 m.y.), and Val do Queve (133.4 ± 11.5 m.y.). In addition we report the first radiometric ages (707.9 ± 59.6 and 705.5 ± 61.0 m.y.) of crustal zircons from kimberlites in northwest Liberia. The fission track ages agree well with earlier age estimates. Most of the zircons examined in this study are zoned with respect to uranium but linear correlations are established (by regression analysis) between zones of variable uranium content, and within zones of constant uranium content (by analysis of variance). Concordance between the fission track method and the U/Pb technique is established and we concluded that track fading from thermal annealing has not taken place. Kimberlitic zircons dated in this study, therefore, record the time of eruption.

Earth and Planetary Science Letters↗

USGS1995

238U-234U-230Th chronometry of Fe-Mn crusts: Growth processes and recovery of thorium isotopic ratios of seawater

Comparison of ( ( 234 U)excess ( 238 U ) "> 234 U) excess ⁄ ( 238 U) and ( ( 230 Th 232 Th "> 230 Th ⁄ 232 Th ) activity ratios in oceanic Fe-Mn deposits provides a method for assessing the closed-system behaviour of 238 U- 234 U- 230 Th, as well as variations in the initial uranium and thorium isotopic ratios of the precipitated metal oxides. This approach is illustrated using a Fe-Mn crust from Lotab seamount (Marshall Islands, west equatorial Pacific). Here we report uranium and thorium isotopic compositions in five subsamples from the surface of one large 5 cm diameter botryoid of this crust, and from two depth profiles of the outermost rim of the same botryoid. The decrease of ( ( 234 U)excess ( 238 U ) "> 234 U) excess ⁄ ( 238 U) and ( ( 230 Th 232 Th "> 230 Th ⁄ 232 Th ) activity ratio with depth in the two profiles gives mean growth rates, for the last 150 ka, of 7.8 ± 2 mm/Ma and 6.6 ± 1 mm/Ma, respectively. All data points (surface and core samples) but one, define a linear correlation in the Ln ( 230 Th 232 Th − Ln ( 234 U)excess ( 238 U ) "> Ln ( ( 230 Th 232 Th "> 230 Th ⁄ 232 Th ) −Ln[ ( ( 234 U)excess ( 238 U ) "> 234 U) excess ⁄ ( 238 U) ] diagram. This correlation indicates that for all points the U-Th system remained closed after the Fe-Mn layer precipitated, and that the different samples possessed the same initial Uranium and thorium isotope ratios. Furthermore, these results show that the preserved surface of this Fe-Mn crust may not be the present-day growth surface, and that the thorium and uranium isotopic ratios of seawater in west equatorial Pacific have not changed during the past 150 ka. The initial thorium activity ratio is estimated from the correlation obtained between Ln ( 230 Th 232 Th − Ln ( 234 U)excess ( 238 U ) "> Ln ( ( 230 Th 232 Th "> 230 Th ⁄ 232 Th ) −Ln Ln ( 230 Th 232 Th − Ln ( 234 U)excess ( 238 U ) ">[ ( ( 234 U)excess ( 238 U ) "> 234 U) excess ⁄ ( 238 U) ] .

Lotab Seamount, Pacific Ocean↗

USGS1979

Disequilibrium in the 238uranium series in samples from Yeelirrie, Western Australia

Uranium-series disequilibrium studies carried out on samples from the Yeelirrie uranium deposit, Western Australia, indicate that uranium and radium have been migrating within the deposit during recent times, and are actually being removed from the deposit. Samples collected for 230 Th/ 234 U age dating were found to be substantially out of equilibrium, with 230 Th/ 234 U activity ratios ranging from 0.750 to 1.345. This can be explained by a dynamic hydrologic system in which there has been, and continues to be, uranium migration caused by leaching in this arid, oxidizing environment, and a fluctuating water table. Recent, extensive 226 Ra migration ( 226 Ra/ 230 Th activity ratios range from 0.53 to 1.30), and a very low emanation factor ( E ) of 222 Rn limit the quantitative application of radon exploration techniques in this environment.

Journal of Geochemical Exploration↗

USGS1998

Radionuclides in fly ash and bottom ash: Improved characterization based on radiography and low energy gamma-ray spectrometry

Two radiation-based techniques for determining the distribution and relative abundance of radionuclides are described, and applied to a suite of fly ash and bottom ash samples from a Kentucky power plant. The technique of fission-track radiography provides new observations of the variety of uranium hosts and of uranium distribution in individual particles of fly ash, and thus aids prediction of the leachability of uranium during long-term disposal or utilization of fly ash. Uranium is largely dispersed within glassy components of fly ash particles and shows little evidence for obvious surface enrichment that could be attributed to secondary adsorption. The technique of low energy gamma-ray spectrometry provides simultaneous, non-destructive determination of the relative abundance of 238 U, 226 Ra, 228 Ra and 210 Pb in representative 150–250 g samples. The measurements provide a means for screening samples to determine if the combustion process causes significant preferential redistribution of radionuclides that could affect their subsequent mobility. Results indicate that radium isotopes are not significantly (within 10–15%) fractionated from parent 238 U and 232 Th during coal combustion. In contrast, 210 Pb appears to be preferentially enriched in some samples of fly ash, and depleted in bottom ash relative to 238 U and 226 Ra. In this application 210 Pb acts as a tracer for elemental lead, and confirms the expected greater volatility of Pb compared to more refractory elements during coal combustion.

Fuel↗

USGS1985

Isotopic studies of the late Archean plutonic rocks of the Wind River Range, Wyoming

Isotopic studies of the Rb-Sr and U-Th-Pb systems in whole-rock samples and the U-Pb systematics for zircons document the existence of two late Arehean intrusive events in the Wind River Range. All of the systems examined indicate an age of ∼2,630 ± 20 m.y. for the Louis Lake batholith. Apparent ages for the Bears Ears pluton range from 2,504 ± 40 m.y. to 2,575 ± 50 m.y. The scatter in apparent ages for the Bears Ears pluton does not appear to be primarily the result of disturbance by postintrusive events, but it may be explained by an isotopically inhomogenous magma at the time of intrusion. Data for a few samples indicate that the Wind River Range was affected locally by a postmagmatic hydrothermal event that was approximately Tertiary in age. This event lowered δ 18 O values and disturbed parent-daughter relationships in most of the isotopic systems investigated, but it was recent enough that there is no demonstrable effect in the Pb-Pb system. The Bears Ears pluton has some chemical and petrologic features that are similar to those reported for the granites in the Granite Mountains to the east. These granites are spatially associated with low-temperature uranium deposits of Tertiary age and have been shown to have lost large amounts of uranium during the early to middle Tertiary. U-Pb systematics indicate, however, that the low to moderate uranium contents and highly variable Th/U values noted for the Bears Ears pluton are best interpreted as being primary features. If uranium was lost after magma generation, the loss most likely occurred at the time of intrusion. Such a loss could account for uraniferous Precambrian pegmatites southwest of the main part of the Range. The two intrusive units apparently were derived from different protoliths that were formed during early to middle Archean. Initial isotopic ratios and petrochemistry for the Louis Lake batholith are consistent with an early Archean trondhjemitic to tonalitic source. The protolith for the Bears Ears pluton must have been more evolved and somewhat younger. Inconsistencies as to the degree of evolution of this protolith, as inferred from isotopic and trace-element data, suggest that the protolith may have been subjected to high-grade meta-morphism that caused loss of Rb and U prior to generation of the magma.

Wyoming↗

USGS1957

Effects of radon in drill holes on gamma-ray logs

Drill holes in uranium deposits in the Todilto limestone of Late Jurassic age near Grants, New Mexico, do not yield duplicate gamma-ray logs when probed at different times; some logs show equivalent uranium greatly in excess, in thickness and grade, of the chemical and laboratory radiometric analyses. Radon and its daughter products principally cause the discrepancies. Experimental work was undertaken by the writers to learn the relations of the radon to the uranium deposits and its behavior under different physical conditions. The work is based on the interpretation of about 600 gamma-ray logs, taken from 480 drill holes.Abnormally high amounts of radon, referred to here as contamination, ranged from barely detectable amounts to amounts that emitted as much radiation as ore-grade material. Most contaminated holes were in the higher-grade ore, and the contamination increased with elapsed time after drilling. Geologic conditions favorable for contamination by radon and its daughter products in drill holes are: proximity to uranium deposits and fractured or highly permeable rocks above the water table. Most drill holes can be decontaminated by blowing them out with compressed air or filling them with water. Water, however, tends to reduce the thickness-times-grade figures below the amounts determined in air.

New Mexico↗

USGS1965

Gamma-ray spectrometer studies of hydro-thermally altered rocks

The uranium, thorium, and potassium content of hydrothermally altered rocks in the vicinity of several copper and copper-lead-zinc deposits in Arizona was determined by chemical analysis. Potassium in the more intensely altered zones is about twice that in unaltered areas. There is no corresponding increase in thorium, so a higher potassium/thorium ratio also results from alteration; abnormally high uranium, locally in secular disequilibrium, was observed at the Bagdad porphyry copper deposit. A truck-mounted gammarray spectrometer was used to obtain a spectrum of gamma emission at each sample location. Equating the spectrometric with the chemical data gave standard errors of 0.6 percent potassium, 3 ppm thorium, and 10 ppm uranium for the outcrop analyses with the spectrometer . The amount of potassium introduced by hydrothermal alteration is thought sufficient in quantity to be detected by either surface or aerial spectrometry; spectrometric detection of anomalous uranium is probably marginal, owing to the disequilibrium. The potassium/thorium ratio may provide a means of distinguishing, in such surveys, between hydrothermally altered high-potassium zones and unaltered extrinsically high-potassium intrusives.

Economic Geology↗

USGS1954

Uranophane at Silver Cliff mine, Lusk, Wyoming

The uranium deposit at the Silver Cliff mine near Lusk, Wyo., consists primarily of uranophane which occurs as fracture fillings and small replacement pockets in faulted and fractured calcareous sandstone of Cambrian (?) age. The country rock in the vicinity of the mine is schist of pre-Cambrian age intruded by pegmatite dikes and is unconformably overlain by almost horizontal sandstone of Cambrian(?) age. The mine is on the southern end of the Lusk Dome, a local structure probably related to the Hartville uplift. In the immediate vicinity of the mine, the dome is cut by the Silver Cliff fault, a north-trending high-angle reverse fault about 1,200 feet in length with a stratigraphic throw of 70 feet. Uranophane, metatorbernite, pitchblende, calcite, native silver, native copper, chalcocite, azurite, malachite, chrysocolla, and cuprite have been deposited in fractured sandstone. The fault was probably mineralized throughout its length, but because of erosion, the mineralized zone is discontinuous. The principal ore body is about 800 feet long. The width and depth of the mineralized zone are not accurately known but are at least 20 feet and 60 feet respectively. The uranium content of material sampled in the mine ranges from 0.001 to 0.23 percent uranium, whereas dump samples range from 0.076 to 3.39 percent uranium.

Bulletin↗

USGS1959

Radioactive rare-earth deposit at Scrub Oaks mine, Morris County, New Jersey

A deposit of rare-earth minerals in the Scrub Oaks iron mine, Morris County, N. J., was mapped and sampled in 1955. The rare-earth minerals are mainly in coarse-grained magnetite ore and in pegmatite adjacent to it. Discrete bodies of rare-earth-bearing magnetite ore apparently follow the plunge of the main magnetite ore body at the north end of the mine. Radioactivity of the ore containing rare earths is about 0.2 to 0.6 mllliroentgens per hour. The principal minerals of the deposit are quartz, magnetite, hematite, albiteoligoclase, perthite and antiperthite. Xenotime and doverite aggregates and bastnaesite with intermixed leucoxene are the most abundant rare-earth minerals, and zircon, sphene, chevkinite, apatite, and monazite are of minor abundance in the ore. The rare-earth elements are partly differentiated into cerium-rich bastnaesite, chevkinite, and monazite, and yttrium-rich xenotime and doverite. Apatite, zircon, and sphene contain both cerium and yttrium group earths. Eleven samples of radioactive ore and rock average 0.009 percent uranium, 0.062 percent thorium, 1.51 percent combined rare-earth oxides including yttrium oxide and 24.8 percent iron. Scatter diagrams of sample data show a direct correlation between equivalent uranium, uranium, thorium, and combined rare^ earth oxides. Both cerium- and yttrium-group earths are abundant in the rare-earth minerals. Radioactive magnetite ore containing rare-earth minerals probably formed as a variant of the magnetite mineralization that produced the main iron ore of the Scrub Oaks deposit. The rare-earth minerals and the iron ore were deposited contemporaneously. Zircon crystals, probably deposited at the same time, have been determined by the Larsen method to be about 550 to 600 million years old (late Precambrian age). Uranium, thorium, and rare-earth elements are potential byproducts of iron in the coarse-grained magnetite ore.

New Jersey↗

USGS1953

Reconnaissance for radioactive deposits in the lower Yukon-Kuskokwim Highlands region, Alaska

Investigations in 1947 in the Lower Yukon-Kuskokwim region, Alaska found that previously reported radioactivity in the vicinity of Flat is due to uraniferous zircon, an accessory mineral in monzonite. The monzonite intrudes mafic igneous and Upper Cretaceous sedimentary rocks. The maximum equivalent-uranium content of the zircon is 0.14 percent, and the average content is probably near 0. 13 percent. Chemical analysis of one sample of the most radioactive zircon indicates approximately 0.12 percent uranium and 0.03 percent thoria. The radioactive elements apparently are most commonly associated with reddish-brown inclusions within the zircon crystals. Tests of sulfide-bearing veins, black shales, and other rock types in the area around Flat showed no significant amount of radioactive material. Although there is little likelihood of finding high-grade uranium deposits in the area covered by the 1947 investigation, the fact that the predominant radioactive element in the monzonite is uranium may indicate that other intrusives of the same age in the Lower Yukon-Kuskokwim region might also contain uraniferous material. Possibilities of concentrations in attendant contact-metamorphic or vein deposits are suggested by a previously reported occurrence of zeunerite in a copper lode in this same general belt of intrusives.

Circular↗

USGS2011

Groundwater quality of the Gulf Coast aquifer system, Houston, Texas, 2010

During March–December 2010, the U.S. Geological Survey, in cooperation with the city of Houston, collected source-water samples from 60 municipal supply wells in the Houston area. These data were collected as part of an ongoing study to determine concentrations, spatial extent, and associated geochemical conditions that might be conducive for mobility and transport of selected naturally occurring contaminants (selected trace elements and radionuclides) in the Gulf Coast aquifer system in the Houston area. In the summers of 2007 and 2008, a reconnaissance-level survey of these constituents in untreated water from 28 municipal supply wells was completed in the Houston area. Included in this report are the complete analytical results for 47 of the 60 samples collected in 2010—those results which were received from the laboratories and reviewed by the authors as of December 31, 2010. All of the wells sampled were screened in the Gulf Coast aquifer system; 22 were screened entirely in the Evangeline aquifer, and the remaining 25 wells contained screened intervals that intersected both Evangeline and Chicot aquifers. The data documented in this report were collected as part of an ongoing study to characterize source-water-quality conditions in untreated groundwater prior to drinking-water treatment. An evaluation of contaminant occurrence in source water provides background information regarding the presence of a contaminant in the environment. Because source-water samples were collected prior to any treatment or blending that potentially could alter contaminant concentrations, the water-quality results documented by this report represent the quality of the source water, not the quality of finished drinking water provided to the public. Samples were analyzed for major ions (calcium, magnesium, potassium, sodium, bromide, chloride, fluoride, silica, and sulfate), residue on evaporation (dissolved solids), trace elements (arsenic, barium, boron, chromium, iron, lithium, manganese, molybdenum, selenium, strontium, and vanadium), and selected radionuclides (gross alpha- and beta-particle activity [at 72 hours and 30 days], carbon-14, radium-226, radon-222, and uranium). Field measurements were made of selected physicochemical (relating to both physical and chemical) properties (oxidation-reduction potential, turbidity, dissolved-oxygen concentration, pH, specific conductance, water temperature, and alkalinity) and unfiltered sulfides. Similar to the results from the reconnaissance survey, physicochemical properties, major ions, and trace elements varied considerably. The ranges of selected physicochemical properties were as follows: oxidation-reduction potential ranged from -173 to 466 millivolts, dissolved oxygen ranged from less than 0.1 to 4.4 milligrams per liter, pH ranged from 7.2 to 7.8, specific conductance ranged from 439 to 724 microsiemens per centimeter at 25 degrees Celsius, and alkalinity ranged from 159 to 276 milligrams per liter as calcium carbonate. The largest ranges in concentration for filtered major ion constituents were obtained for cations sodium and calcium and for anions chloride and sulfate. Arsenic concentrations measured in samples from the 47 wells ranged from 1.6 to 23.5 micrograms per liter. The maximum concentration of arsenic (23.5 micrograms per liter) was measured in the source-water sample from well LJ-65-12-328. Quantifiable concentrations of barium, boron, lithium, molybdenum, and strontium were measured in all 47 filtered, source-water samples. Quantifiable concentrations of manganese were measured in 46 source-water samples, and an estimated concentration of manganese was measured in 1 sample. Chromium, iron, selenium, and vanadium were detected in 24 or more of the 47 source-water samples. Gross alpha-particle activities and beta-particle activities for all 47 samples were analyzed at 72 hours after sample collection and again at 30 days after sample collection, allowing for the measurement of the activity of short-lived isotopes. Gross alpha-particle activities reported in this report were not adjusted for activity contributions by radon or uranium and, therefore, are conservatively high estimates if compared to the U.S. Environmental Protection Agency National Primary Drinking Water Regulation for adjusted gross alpha-particle activity. The gross alpha-particle activities at 30 days in the samples ranged from R0.60 to 25.5 picocuries per liter and at 72 hours ranged from 2.58 to 39.7 picocuries per liter, and the "R" preceding the value of 0.60 picocuries per liter refers to a nondetected result less than the sample-specific critical level. Gross beta-particle activities measured at 30 days ranged from 1.17 to 14.4 picocuries per liter and at 72 hours ranged from 1.97 to 4.4 picocuries per liter. Filtered uranium was detected in quantifiable amounts in all of the 47 wells sampled. The uranium concentrations ranged from 0.03 to 42.7 micrograms per liter. One sample was analyzed for carbon-14, and the amount of modern atmospheric carbon was reported as 0.2 percent. Six source-water samples collected from municipal supply wells were analyzed for radium-226, and all of the concentrations were considered detectable concentrations (greater than their associated sample-specific critical level). Three source-water samples collected were analyzed for radon-222, and all of the concentrations were substantially greater than the associated sample-specific critical level.

Texas↗

USGS2007

Methods and data used to investigate polonium-210 as a source of excess gross-alpha radioactivity in ground water, Churchill County, Nevada

Ground water is the major source of drinking water in the Carson River Basin, California and Nevada. Previous studies have shown that uranium and gross-alpha radioactivities in ground water can be greater than U.S. Environmental Protection Agency Maximum Contaminant Levels, particularly in the Carson Desert, Churchill County, Nevada. Studies also have shown that the primary source of the gross-alpha radioactivity and alpha-emitting radionuclides in ground water is the dissolution of uranium-rich granitic rocks and basin-fill sediments that have their origins in the Sierra Nevada. However, ground water sampled from some wells in the Carson Desert had grossalpha radioactivities greater than could be accounted for by the decay of dissolved uranium. The occurrence of polonium-210 (Po-210) was hypothesized to explain the higher than expected grossalpha radioactivities. This report documents and describes the study design, field and analytical methods, and data used to determine whether Po-210 is the source of excess gross-alpha radioactivity in ground water underlying the Carson Desert in and around Fallon, Nevada. Specifically, this report presents: 1) gross alpha and uranium radioactivities for 100 wells sampled from June to September 2001; and 2) pH, dissolved oxygen, specific conductance, and Po-210 radioactivity for 25 wells sampled in April and June 2007. Results of quality-control samples for the 2007 dataset are also presented.

Open-File Report↗

USGS2009

Geochemical Analyses of Rock, Sediment, and Water from the Region In and Around the Tuba City Landfill, Tuba City, Arizona

The Tuba City Landfill (TCL) started as an unregulated waste disposal site in the 1940s and was administratively closed in 1997. Since the TCL closure, radionuclides have been detected in the shallow ground water. In 2006, the Bureau of Indian Affairs (BIA) contracted with the U.S. Geological Survey (USGS) to better understand the source of radionuclides in the ground water at the TCL compared to the surrounding region. This report summarizes those data and presents interpretations that focus on the geochemistry in the rocks and water from the Tuba City region. The TCL is sited on Navajo Sandstone above the contact with the Kayenta Formation. These formations are not rich in uranium but generally are below average crustal abundance values for uranium. Uranium ores in the area were mined nearby in the Chinle Formation and processed at the Rare Metals mill (RMM). Regional samples of rock, sediment, leachates, and water were collected in and around the TCL site and analyzed for major and minor elements, 18O, 2H, 3H, 13C, 14C,34S, 87Sr, and 234U/238U, as appropriate. Results of whole rock and sediment samples, along with leachates, suggest the Chinle Formation is a major source of uranium and other trace elements in the area. Regional water samples indicate that some of the wells within the TCL site have geochemical signatures that are different from the regional springs and surface water. The geochemistry from these TCL wells is most similar to leachates from the Chinle Formation rocks and sediments. Isotope samples do not uniquely identify TCL-derived waters, but they do provide a useful indicator for shallow compared to deep ground-water flow paths and general rock/water interaction times. Information in this report provides a comparison between the geochemistry within the TCL and in the region as a whole.

Open-File Report↗

USGS1956

Geology and ore deposits of the Monument Valley area, Apache and Navajo Counties, Arizona

In 1951 the U.S. Geological Survey undertook a program of uranium investigations in Apache and Navajo Counties, northeastern Arizona. The work had three major objectives. The first was to accumulate data basic to an understanding of the regional geology. The second was to appraise the Triassic strata as host rocks for uranium deposits, and to select areas favorable for exploration for concealed deposits. The third objective was to study the controls that influence uranium deposition and from this study, to establish guides useful in prospecting for uranium deposits.

Arizona↗