Abstract: Results of Pilot Studies of Project NURE from New Mexico: Estancia Basin and Area Northeast of Grants Mineral Belt
Douglas G. Brookins, Clayton E. Olsen
Pilot studies for Project NURE (National Uranium Resources Evaluation) were conducted in the Estancia basin and in an area northeast of the well-known Grants mineral belt to test water and stream-sediment sampling practices and analytic methods, and to allow assessment of these and other parameters. Uranium was analyzed by the delayed neutron-activation method; precision and accuracy of this method are excellent (± 2% at the 99% confidence level) even in the 1 to 10-ppb range.
The Estancia basin is a closed basin with terminal drainage into a playa-bolson area. Computer contouring of data from 500 well-water analyses indicates two highs, one with >300 ppb U in the playa-bolson area and one with >100 ppb over the southern part of the Pedernal Hills. Stream-sediment highs in the basin were noted in the northwest part (XU = 3.18 ppm; n = 982), the southeast part (XU = 2.58; n = 395), and in the southwest part (XU = 2.84 ppm; n = 864). The entire basin stream sediments yield XU = 2.90; n = 3,094. The local highs can be correlated with U contents of probable source rocks; surprisingly high (to 20 ppm) U contents were determined in Phanerozoic shale-limestone sequences. Precambrian granites (3.70 ppm) and metasedi entary rocks (2.10 ppm) probably contributed less U than the Phanerozoic rocks.
In the area northeast of and parallel with the Grants mineral belt no closed basins are in the northeasterly-trending drainage pattern. U content of 275 water wells ranges from <1 ppb to 1.26 ppm; 1,545 stream sediments range from < 1 to ~ 40 ppm (X = 3.36 ppm). Direct correlation of high U content in well water and stream sediments cannot be made; yet high concentrations appear to be from local sources and not caused by the Grants mineral belt.
AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC