The Mount Taylor uranium deposit in the Grants mineral belt of New Mexico resembles the roll-front deposits of the Wyoming Tertiary basins in many respects. First, the deposit is spatially related to paleochannel systems in the arkosic sandstones of the Jurassic Morrison Formation. Second, the orebody has a cross-sectional form which is crudely C-shaped. It is also elongated along strike. Third, the trace elements arsenic, selenium, and molybdenum, which are known to occur in zones through the Wyoming rolls, do so in this deposit as well. Fourth, a calcite halo is present as cement in the sands near the outer downdip limits of ore. Finally, the host sediments were derived by weathering granites and are overlain by a fairly thick sequence of continental tuffaceous mudstone .

The Mount Taylor deposit differs from the Wyoming deposits in one significant aspect--it does not reside at an iron redox interface. This deposit is not rich in pyrite, and hematite is not present immediately behind (updip from) the ore. Also, primary uranium-bearing minerals have not been identified in the Mount Taylor ore.

Organic carbon is associated with the Mount Taylor ore and probably served as a reducing precipitant for much of the uranium present in the deposit. Certain complexities in this relation imply, however, that organic molecules may have been an important factor in transporting uranium to points of precipitation.

Montmorillonite, chlorite, and kaolinite form a zonation pattern from unaltered downdip rock through the ore and into altered updip rock. Limited data suggest that this clay mineral zonation may not be associated with the Wyoming roll-front deposits.

End_of_Article - Last_Page 839------------