Dry Valley Mining District, San Juan County, Utah, USAi

Regional Level Types
Dry Valley Mining District	Mining District
San Juan County	County
Utah	State
USA	Country

The Dry Valley (East Canyon) district of the Monticello U mining area is in northeastern San Juan County, about 40 mi southeast of Moab. The district is a large V-U producer and has reported production from about 1945 to 1980. Total district metal production at modern metal prices is estimated at $122 million. Dry Valley produced about 1,525,000 pounds U3O8 and 12,662,000 pounds V2O5 at average grades of 0.15% U3O8 and 1.30% V2O5 through 1980. The Dry Valley district is the third largest V producer in Utah. The largest operations are in the Rim-Columbus-Sunset underground mine area (Doelling, 1969, 1974).
The Dry Valley district is in the Paradox Basin on the Colorado Plateau. The primary host is the Upper Jurassic Salt Wash Member of the Morrison Formation with most of this production from the upper sandstone unit of the Salt Wash. The Salt Wash Member averages about 300 ft thick in the Dry Valley district and consists of a lower, generally continuous sandstone unit averaging about 30 ft thick, a middle unit with several thin (10 to 25 ft thick) discontinuous sandstone lenses, and an upper, generally continuous sandstone unit 15 to over 80 ft thick with occasional 10- to 20-ft-thick shale interbeds. The larger and more concentrated groupings of deposits occur where this upper, continuous sandstone is at least 40 ft thick (Doelling, 1969, 1974).
According to Doelling (1969), the tabular orebodies typically measure 3 ft thick by 30 ft wide by 200 ft long with the elongation dimension generally parallel to the channel (USGS Model 30c). In the major ore producing areas, the lenticular roll deposits are from 3 to 10 ft thick, 50 to 150 ft wide, and 100 to as much as 500 ft long. Both tabular and roll type orebodies can occur at any level within the host channel but are generally near the bottom or sides (Doelling, 1969). In general, the ore minerals fill voids, impregnate the host sandstone, and locally replace carbonaceous material. Within the tabular orebodies, mineralization often consists of a series of irregular, thin, wispy zones of more concentrated ore. The unoxidized ore consists of uraninite, coffinite, montroseite, and vanadium micas; however, most of the ore mined was oxidized and consisted of vanadium mica/ vanadium clays, carnotite, tyuyamunite, corvusite, and occasionally volborthite.