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

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

The Lisbon Valley mining district is located about 34 mi southeast of Moab in northeastern San Juan County. The district had a desultory history following its organization in 1892 as an intermittent Cu producer prior to the discovery of the Mi Vida U mine by Charlie Steen in 1953, which began over three decades of uninterrupted U production. Important open pit, SX-EW Cu production began in 2006. The district is roughly the eighth most productive district in Utah. The Lisbon Valley district is the largest U and third largest Cu producer in the state. Total district metal production at modern metal prices is estimated at $2.7 billion. The most productive U properties are the Lisbon mine, Hecla Shaft, Mi Vida mine, and Velvet shaft. The most productive Cu mines are the Centennial, GTO, and Sentinel open pits. These major Cu mines are still in production.
Geologically, the Lisbon Valley district is in the Paradox Basin on the Colorado Plateau. The Paradox Basin is underlain by about 7000 ft of Pennsylvanian-age restricted marine evaporites, black shale, and carbonate rocks. The Pennsylvanian strata are overlain by 1900 ft of Permian- and Triassic-age shale and fluvial sandstone followed by another 4200 ft of Jurassic- and Cretaceous-age eolian sandstone and shale. Within this section, the primary host rocks are the Permian Cutler Group sandstone (U-V, Cu), the Triassic Moss Back Member of the Chinle Formation (U), and the Cretaceous Burro Canyon Formation and Dakota Sandstone (Cu). The district is centered on the northwest-trending Lisbon Valley anticline, a large (11-mi-long), upright, open, doubly plunging fold. The anticline has a sub-parallel, large displacement (about 5000 ft), northeast-dipping, normal fault just northeast of its crest. The Lisbon Valley anticline began to form in the Early Triassic followed by movement on the Lisbon Valley fault in the Late Triassic (Chenoweth, 2006). Most of the known U mineralization is on the up-thrown side of the Lisbon Valley fault and follows the erosional contact between a 50-ft-thick white sandstone (“sugar sand”) in the upper part of the Cutler Group and the overlying Moss Back Member of the Chinle Formation (USGS Model 30c). Mineralization precipitated at the interface probably between U-rich oxidizing groundwater in the Moss Back and reducing hydrocarbon and hydrogen sulfide (H2S)-bearing fluid in the underlying Cutler.
The Lisbon Valley Cu deposits are much younger and are formed by brines expelled along the Lisbon Valley fault. The Cu- bearing fluid may have been a deeply circulating meteoric water that leached Cu from the thick sequence of underlying Cutler red beds in the hanging wall of the Lisbon Valley fault prior to precipitation in the bleached and reduced sandstones (USGS Model 30b). All major Cu orebodies are in the hanging wall of the main fault and are often associated with subsidiary faults (Hahn and Thorson, 2006).

The district was originally established as the Big Indian mining district in 1892 following the discovery of oxidized copper ore. Around 1903, copper ore was mined in Big Indian Valley. The district became inactive due to low copper prices, but was re-established as the Lisbon Valley district in 1913 when the first outcropping of uranium-vanadium ore was encountered in the area. The first recorded vanadium production came from the Divide and Service Berry mines in 1917. Copper ore was later mined by open-pit methods at the Big Indian Copper mine during World War II. In 1948, Dan Shays of Monticello, Utah found uranium-bearing exposures and located the Big Buck claims. All of these mines produced small-scale shipments of ore until Charlie Steen’s discovery on July 6, 1952, when he located unoxidized uranium ore after drilling 70 feet into sandstone. This discovery was made without the aid of a Geiger counter, which detects the radioactivity of uranium. All discoveries prior to and after this discovery relied heavily on the aid of the Geiger counter. Charlie Steen’s mine, called Mi Vida, produced a total of 6,150 tons of uranium until its closure in 1962. This mine became the largest producer of uranium in the district, yielding about 16 percent of the total production. Other mines in the district include the Homestake, Small Fry, Velvet, and Libson mines. Low uranium prices and a weak market in the early 1980s forced many of the mines to cease operations. In late 1988, mining operations in the district ceased with the closure of Rio Alsom’s Lisbon mill, located south of La Sal.