60 Understanding Water Resources related to Mineralized Uranium Deposits in the Southwestern United States

Thursday, 17 May 2018
8:20 AM - 10:05 AM
Kaibab Room

UNDERSTANDING WATER RESOURCES RELATED TO MINERALIZED URANIUM DEPOSITS IN THE SOUTHWESTERN UNITED STATES

Paper number: 60-3
Program: Theme Sessions
Time: 8:45 AM – 9:05 AM

Authors

Abstract

New Mexico has a uranium-mining legacy dating back to early discoveries in the 1920s. The larger scale uranium mining in New Mexico was driven by the need of uranium in atomic bomb production after World War II combined with the discoveries of the sand-stone hosted deposits in the Grants mining district. There are many small deposits and occurrences outside the Grants mining district as well, some that are sandstone hosted, as well as vein type deposits/occurrences associated with Rio Grande Rift activity. Human activities associated with uranium mining have resulted in mine features that have not been characterized. Waste associated with mines can pose health and environmental risks and in some cases require monitoring by government agencies. Tools to help characterize the risks these sites pose include kinetic tests, in which mine material is placed in a column and subjected to simulated weathering conditions. These tests help evaluate leaching potential of waste rocks and help anticipate the quality of mine drainage from a given site.

In this project, waste rocks were collected from two mines within the Grants Mining District, St. Anthony Mine in the Laguna Sub-district and Section 11/12 mine in the Ambrosia Lake Sub-district, together with Jeter mine northeast of the Sierra Ladrones. Material from these mines was subject to long-term kinetic testing with mineralogical and geochemical analysis conducted on the material before and after. The sulfide content is low to absent in several of the samples. Uraninite is the most common mineral in the samples, however, secondary autunite was also identified.

During the kinetic test, the columns were treated weekly to bi-weekly with deionized water, and the drainage analyzed for pH, specific conductance, major anions and cations, and trace metals. The leaching shows that column material with alkaline drainage (a maximum pH of 8.5) has as high a potential to generate soluble uranium as material generating weakly acidic (lowest pH of 4 in the columns) drainage. At neutral pH uranium mobility is at the lowest. This indicates that alkaline leach from waste piles can be as problematic with respect to uranium mobility as acid drainage.

Geological Society of America Abstracts with Programs. Vol. 50, No. 5

doi: 10.1130/abs/2018RM-314439

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