Gateway Mining District, Grand County, Utah, USAi

Regional Level Types
Gateway Mining District	Mining District
Grand County	County
Utah	State
USA	Country

The Gateway (Beaver Mesa, Polar Mesa) district is in eastern Grand County about 25 mi east-northeast of Moab. The district is a significant U-V producer. Total district metal production at modern metal prices is estimated at $66 million. The U mineralization in the Gateway district extends into adjoining portions of Colorado as the northern Uravan mineral belt. The largest producers are the Effie F., Petrified Tree, F.W. #3, and Thompson C underground mines. These deposits are all clustered in the northwest corner of the district.
Gateway lies in the Paradox Basin on the Colorado Plateau on the very gently dipping, southwest limb of the Sagers Wash syncline. The Upper Jurassic Salt Wash Member of the Morrison Formation is the primary U-V host in the district (USGS Model 30c). The Salt Wash Member here is slightly over 300 ft thick and ore occurs predominantly in the light-brown to light-gray, 10- to 80-ft thick, “Payoff” sandstone horizon in the upper portion of the unit (Doelling, 1974). Minor mineralization also occurs in the basal Brushy Basin Member and at the base of the Upper Triassic Chinle Formation.
Mineralization is associated with fossilized logs, carbonized vegetal matter, and seams of mudstone. Individual orebodies are small, tabular, amoeboid-shaped, elongated in a northeast direction and range in size from 100 to 5700 tons, and the deposits tend to cluster into larger ore zones (Doelling, 1974). Both oxidized and unoxidized ores are known, but unoxidized ores are the most important producers. Pyrite is abundant in the ores along with uraninite, coffinite, montroseite, and doloresite (Doelling, 1974). The ores typically average about 0.3% U3O8 and 1.2% V2O5. The Whirlwind mine along the Colorado border has a permitted resource of 169,129 tons at 0.3% U3O8 and 0.7% V2O5.