New Mexico Geological Society Annual Spring Meeting — Abstracts

The Grants Mineral District in New Mexico was a major uranium producing area in the world (McLemore, 2010), and it was one of the primary three uranium-mining districts from the 1950s to late 1980s. In the nature, uranium is mobile as uranyl and carbonate complexes, it forms stable minerals in reducing conditions. This is the case in the Morrison Formation; a sandstone unit in the Grants Mineral District shows locally radiation anomalies due to uranium bearing layers. In addition, historic mining and milling of uranium ore has led to widespread contamination of shallow ground water resources (Thomson et.al, 2014). Arroyos in the vicinity of Ambrosia Lake have shown some evidence of uranium contamination. Although the mine site has previously been reclaimed, contamination from the mine site are still occurring (Jaramillo, 2013). In an attempt to determine mineral sources of the contamination and transformations associated with uranium chemistry, we are conducting preliminary leaching tests on the waste rock from Section 11/12 mine, Saint Anthony Mine and the Mt. Taylor Mine to evaluate the geochemical behavior of mining material from the Grants Mining District. Characterizing the wastes to evaluate the current and future leaching potential is essential for the public health.
A series of laboratory experiments are being conducted to assess the mineralogy and geochemistry of the material to estimate the leaching potential, acid generation and neutralization potential. Kinetic Column Tests (KCTs) have been constructed for uranium leaching tests, which provide the closest analogue to the infiltration of water through solids or aquifers (Nordtest, 1995b). The assumption applied to this test is that if the constituent doesn’t leach from the waste, then it is not a threat to the groundwater. Therefore, most of the subsequent chemical experiments will be conducted twice, before KCTs and after KCTs, to compare the differences of initial and final metal concentrations and constitute species. In addition, weekly tests for pH, conductivity, Pe, alkalinity, major anions, major cations and trace elements are being conducted on the column leachate. This data is being used to compare changes from week to week to determine points in time where the data stabilizes.