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At least 1,009 records · Page 56Linked to original sources
USGS1987

The solubilities of some major and minor element minerals in ground waters associated with a sandstone-hosted uranium deposit

Ground-water samples from 41 wells penetrating basal Oakville sandstone (Miocene) in S Texas were chemically analysed to identify chemical changes related to nearby U orebodies. The coverage included a 240 km 2 area which contains several fault-related U deposits. Factors affecting the hydrochemistry include: 1) relatively high permeabilities of buried fluvial-channel sediments; 2) upwards leakage of brines along growth faults into the aquifer; 3) development of a redox interface (Eh = 0 volts) within the aquifer; and 4) the semi-arid climate. Variations in the saturation index (SI) for chemically reduced minerals of U, As, Mo, Se and for associated minerals such as pyrite outlined the position of known deposits. The SI increases towards zero as the deposits are approached from updip distances of 3-4.5 km, then decreases again downdip. The radiogenic pathfinders Ra and Rn showed very strong anomalies with ore, but diminished to background levels at short distances from ore. A strong He anomaly is deflected in the direction of ground-water flow away from the ore.-R.A.H.

Bulletin de Mineralogie↗
USGS1993

Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ?? 1, 30 ?? 3, 45 ?? 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

Conference Paper↗
USGS2000

Groundwater/surface-water interactions and sources of nitrogen and uranium in an irrigated area of Nebraska, USA

The effects of irrigation canals and the North Platte River on groundwater in western Nebraska, USA, were evaluated using chemical and isotopic data. The data indicated that groundwater in the associated alluvium generally is <20 years old with estimated recharge rates from about 10 to >100 cm year -1 . Most groundwater is derived from surface water, as shown by H 2 O and U isotope analyses. Seasonal losses of canal water to the aquifer cause changes in groundwater quality. In the deepest parts of the alluvium, some water quality may reflect precipitation recharge, older river water, or cross-formational flow. The distribution and isotopic composition of NO 3 - are consistent with increased fertilizer use over time. Relatively high U concentrations in groundwater may be attributed to dissolution of volcanic ash or other minerals in underlying bedrocks. The relatively high concentration of U in surface water at times is attributed to seepage from U-rich groundwater and flow of U-rich surface water from a tributary. The effects of irrigation canals and the North Platte River on groundwater in western Nebraska, USA, were evaluated using chemical and isotopic data. The data indicated that groundwater in the associated alluvium generally is <20 years old with estimated recharge rates from about 10 to >100 cm year -1 . Most groundwater is derived from surface water, as shown by H 2 O and U isotope analyses. Seasonal losses of canal water to the aquifer cause changes in groundwater quality. In the deepest parts of the alluvium, some water quality may reflect precipitation recharge, older river water, or cross-formational flow. The distribution and isotopic composition of NO 3 - are consistent with increased fertilizer use over time. Relatively high U concentrations in groundwater may be attributed to dissolution of volcanic ash or other minerals in underlying bedrock. The relatively high concentration of U in surface water at times is attributed to seepage from U-rich groundwater and flow of U-rich surface water from a tributary.

IAHS-AISH Publication↗