South Henry Mountains Mining District, Garfield County, Utah, USAi

Regional Level Types
South Henry Mountains Mining District	Mining District
Garfield County	County
Utah	State
USA	Country

The South Henry Mountain (Little Rockies, Shootaring, Delmonte) mining district lies in eastern Garfield County about 40 mi south of Hanksville. Beginning in the 1950s and operating into the early 1980s, the district became a significant U-V producer. The numerous historical U-V mines were mostly small, but had moderate grade, averaging about 0.3% U3O8. Total district metal production at modern metal prices is estimated at $24 million. Although none of the individual historical operations had important production, significant U reserves were discovered at the Tony M, Copper Bench, and Frank M mines in the late 1970s and largely remain undeveloped.
The South Henry Mountain district occurs in the southern Henry Mountains of the Colorado Plateau. The U-V deposits in the Henry Mountains occur in the Upper Jurassic Salt Wash Member of the Morrison Formation. Nearly all deposits occur along a northerly trending exposure of the Morrison Formation on the east flank of the Henry structural basin. Mineralization is peneconcordant and associated with carbonaceous trash, fossil wood, and mudstone lenses in the fluvio-lacustrine sandstone host rocks (USGS Model 30c). The mined uranium deposits of the Henry Mountains are typically small oxide bodies, and the mean size of the deposits is about 80 tons of ore. Coffinite and tyuyamunite are the principal ore minerals with subordinate autunite (Chenoweth, 1980; Northrop and others, 1986a).
The large South Henry Mountain district mineral resources are typical tabular, uranium-vanadium deposits hosted in fluvial sandstone of the Salt Wash Member. The host sandstone ranges from 30 to 40 ft thick and occurs 10 to 100 ft above the base of the Morrison Formation (Chenoweth, 1980). The mineralized zones are characteristically argillaceous and carbonaceous sandstone. These zones occur as multiple uraniferous horizons associated with and enclosed within a broader vanadium-rich interval and haloed by dolomite-cemented sandstone (Northrop and others, 1986a; Northrop and others, 1986b). These larger U-V resources consist of closely spaced clusters of smaller deposits.