Geology and development of Marquez, New Mexico, uranium deposit

Uranium deposition in the Marquez, New Mexico, area occurs almost exclusively in the lower Westwater Canyon Member of the Morrison Formation (Jurassic). The average aggregate thickness of the Westwater Canyon is 295 ft (90 m), but it ranges from a minimum of 239 ft (73 m) to a maximum of 328 ft (100 m). A K shale separates the upper and lower Westwater Canyon sandstone boundaries. The lower Westwater Canyon sandstone development is more pronounced in an east-southeast direction parallel with the strike of the orebody(ies). Three distinct ore zones were deposited in peneconcordant elongate patterns. The upper zone occupies a stratigraphic interval just below the K shale, and two lower zones lie above and below the K1 shale. Coffinite and uraninite predominate as the stable uranium species; other extrinsic elements were added during the mineralization process. Humates undoubtedly exerted major control on formation of the uranium. Ferrous iron pervades both within and outside the deposit, whereas ferric iron, although limited in quantity, is confined principally to the orebody(ies). The lower K1 shale, parameters of permeability, and recurrence of meanders along the paleochannels also seem to influence enrichment. Surface drilling is continuing, a vertical mine shaft to approximately 2,100 ft (640 m) is nearing completion, and a mill is being constructed on the property