Abstract
Since the early 1950s Poison Canyon has been a classic example of uranium geology. At the present time, because of economic conditions, a closer examination of the redistributed mineralization is being made.
Because of the evolution of the structure and geomorphology of Poison Canyon, the primary mineralization went through further oxidation and reduction. Enriched solutions of uranium migrated downdip through permeable sandstones, with calcium replacing silica near mudstone contacts. These solutions were controlled by north-trending fracture patterns, with some vertical movement along major faults. The uranium collected in structural and lithologic traps, then oxidized, forming amoebalike orebodies with the higher grade mineralization located in the fractures. The authigenic mineral is mainly tyuyamunite in the hexavalent state in sands deficient in carbon and associated, although rarely, with pascoite and ilsemannite.
The equilibrium of the primary minerals differs from that of the redistributed minerals. The uranium has been leached from the primary minerals causing chemical values to be less than radiometric. The redistributed minerals are chemically greater than radiometric, producing a favorable equilibrium. Also, the percent extraction in the mill process is greater for the redistributed ore than the primary ore. The paragenetic position of the different minerals has a direct bearing on these observations.
