Blue Mountain Mining District, Beaver County, Utah, USAi

Regional Level Types
Blue Mountain Mining District	Mining District
Beaver County	County
Utah	State
USA	Country

The Blue Mountain district is in south-central Beaver County about 25 mi southwest of Milford. The district is a minor Fe-Mn producer with a history of just a few iron ore shipments for flux, possibly totaling 500 tons. Total district metal production at modern metal prices is estimated at $24,000. The Emma mine was probably the largest operation, where small Fe gossans were exploited along high-angle faults.
The Blue Mountain district lies astride the east-trending, Miocene, Blue Ribbon lineament of Rowley and others (1978) in the Basin and Range Province. The district encompasses the Blue Mountain, Jockey Road, Iron Mountain, and Iron Mine Wash areas. The primary structure on Blue Mountain proper is a north-south-trending doubly plunging anticline with a window through upper plate Cambrian strata of the Blue Mountain thrust into lower plate Navajo Sandstone, Chinle Formation, and Moenkopi Formation (Weaver and Hintze, 1993). An aeromagnetic high correlates with the crest of the dome indicating an intrusive at depth. The Jockey Road area flanks Blue Mountain to the northwest and consists of rolling hills underlain by upper Cambrian strata unconformably overlain by Oligocene intermediate tuffs and flows.
Mineralization at Blue Mountain proper consists of weak Mo-Cu-Zn skarn/replacement mineralization in the core of the anticline. The Jockey Road and Iron Mine Wash areas have jasperoids and weak sedimentary and volcanic rock-hosted Au mineralization. Several groups have explored the Jockey Road area mostly for low-grade, disseminated Au (USGS Model 19c) over the past three decades. The best sedimentary rock-hosted mineralization occurs in the lower portion of the Middle Cambrian strata including the Chisholm Formation, Dome Limestone, Whirlwind Formation, and the Swasey Limestone just above the Blue Mountain thrust.
The strongest alteration and Au mineralization occur in the center of a northwest-trending graben in clay-silica altered Oligocene volcanic rocks and in heavily silicified rocks of the lower Middle Cambrian sedimentary strata (Weaver and Hintze, 1993). The best Au prospects are a gray, sucrose, vuggy, and brecciated jasperoid with trace pyrite and Au, which occurs not far above the Blue Mountain thrust and about 3.8 mi northwest of the apex of the Blue Mountain dome. In addition to Au and Ag, the area is anomalous in As, Hg, Mo, and Sb.
The iron ore production has come from gossanous Fe-Mn fault zones cutting Cambrian carbonate in the Iron Mountain area on the west end of the district. The polymetallic veins at the Cobolt #1 prospect have very high Fe, Mn, Ni, and Co.