Gold City Mining District, Salt Lake County, Utah, USAi

Regional Level Types
Gold City Mining District	Mining District
Salt Lake County	County
Utah	State
USA	Country

The Gold City (Little Willow) mining district is in Salt Lake County about 12 mi south-southeast of Salt Lake City. The district began with the discovery of gold in the Wasatch foothills which led to the Gold City mining boom from about 1894 to 1901. This boom resulted in the location of many mining claims followed by some mine development, construction of mills, and minor Au production primarily in the early 1900s. As with many Utah Au districts, the properties were closely reexamined during the depths of the Great Depression in the 1930s. The New State and adjoining Wasatch Utah Au mines were the primary producers (James, 1979).
The Gold City district is on the west flank of the Wasatch Range of the Middle Rocky Mountain province. The district is situated in Proterozoic metamorphic rocks near the northern contact of the 50-sq-mi Oligocene Little Cottonwood quartz monzonite batholith. A small, isolated body of quartz monzonite lies about a mile and a half to the north of the batholith in the Gold City district. These metamorphic rocks primarily belong to the Paleoproterozoic Little Willow Formation and Mesoproterozoic Big Cottonwood Formation (James, 2006). The most productive mines are in the Little Willow Formation. The principal rock types are gray quartz-feldspar-biotite gneiss with thin intercalated mafic actinolite schist and quartz-sericite-chlorite schist.
There are two primary types of ore in the Gold City district: steeply dipping, Au-Ag-Cu bull quartz veins with minor chalcopyrite and pyrite; and a few W-bearing quartz veins with pyrite, huebnerite, and scheelite. The precious metal-rich bull quartz veins have provided virtually all of the district’s mineral production. Most of the area developed for Au-Ag also contains thin quartz- sericite-chlorite schist units, but the actinolite schists are the primary host for the Au-Ag-Cu quartz veins. The Wasatch Utah glory hole, for example, produced a few thousand tons of ore from this schist (James, 1979). The ore mineral is native gold or electrum (James, 2006).