GEOLOGIC CONTROLS OF URANIUM RECOVERY OF GRANTS URANIUM DEPOSITS, NEW MEXICO

New Mexico ranks 2nd in uranium reserves in the U. S., which amounts to 15 million tons of ore at 0.277% U3O8 (84 million lbs U3O8) at $30/lb (EIA, 2006). The most important host rock in the state is sandstone within the Morrison Formation (Jurassic) in the Grants district. More than 340 million pounds of U3O8 have been produced from these deposits from 1948-2002, accounting for 97% of the total production in New Mexico and more than 30% of the total production in the United States. Sandstone uranium deposits are defined as epigenetic concentrations of uranium in fluvial, lacustrine, and deltaic sandstones. Three types of sandstone uranium deposits are recognized in the Grants district: primary tabular (primary, trend, blanket, black-band), redistributed (roll-front, post-fault, secondary, fault-related, stack), and remnant deposits. Uranium recovery methods from the different deposit types are controlled by differences in mineralogy and chemistry. Primary tabular, redistributed, and remnant sandstone deposits are amenable to conventional recovery methods (i.e. milling). Redistributed deposits can be recovered by in-situ recovery methods. Evidence suggests that two stages of redistributed deposits could exist in the district—Cretaceous age (redistributed primary roll fronts or redistributed deposits during Cretaceous) and Tertiary age (redistributed from primary and Cretaceous roll fronts).