Abstract: Exploration and Development in Grants Uranium Region, New Mexico

Alva E. Saucier

The Grants uranium region is a discontinuous belt of uranium deposits extending almost 100 mi (160 km) along the shallow, south rim of the San Juan basin in New Mexico. Between 1948 and 1975, New Mexico produced 112,684 tons (101,614 MT) of uranium oxide, 96% of which came from the Morrison Formation. This was 40% of all U.S. production. The Westwater Canyon Sandstone Member of the Morrison is by far the most prolific host rock. The ore in the Westwater is in long, narrow, linear trends with mineralization commonly scattered in overlapping tabular bodies through 200 to 300 ft (60 to 90 m) of section. Drilling along trend has been the most successful exploration technique. Holes are widely spaced along fences normal to the expected trend with closer spaced follow-up drilli g where mineralization is indicated. Most of the drilling is deeper than 2,000 ft (600 m), and one orebody is as deep as 4,700 ft (1,400 m). Drilling costs have more than doubled in the past few years, and in addition, land is expensive and large parcels are difficult to obtain. In many respects, this district is to the uranium industry what offshore exploration is to the petroleum industry. Development drilling runs into millions of dollars before a deposit is proved economic, and it takes 7 to 10 years to put a property into production.

The Grants uranium region is reaching a mature stage of exploration. The south, east, and west limits of the belt have been defined fairly well, and exploration now is downdip to the north. This district is unique in this country in having the largest open-pit uranium mine, the largest mill, and soon will have the deepest underground mine. With half the known U.S. reserves, the Grants uranium region will play an expanding roll in supplying this nation's energy needs.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC