Gold Hill Mining District (Clifton Mining District), Tooele County, Utah, USAi

Regional Level Types
Gold Hill Mining District (Clifton Mining District)	Mining District
Tooele County	County
Utah	State
USA	Country

The Gold Hill mining district is one of the oldest in Utah. It was discovered around 1857 by travelers heading to California through Overland Canyon, located just 6 miles south of the town of Gold Hill. Rich lead-silver surface deposits were discovered and the area was inundated with prospectors and miners. Mining began in 1869 and continued until 1875. Following a brief period of inactivity, mining renewed in 1892, when the first mills began operating. Production lasted until 1904. Over 50 mines were developed, but fewer than half shipped any substantial ore. The towns of Gold Hill and Clifton grew in 1917 with the development of the Deep Creek Railroad, a branch line of the Western Pacific Railroad. During this year, production was greater than in any previous year. In 1920, production of arsenic became important, as significant amounts were mined from the Gold Hill and U.S. mines. Arsenic ore was in great demand for the manufacture of an insect repellant used in the cotton fields of the South. Because of foreign competition, the U.S. arsenic market collapsed in 1925, which caused the area to become a virtual ghost town. From 1926 to 1940, only small-scale mining operations continued, mainly exploration and rehabilitation. The district became important during World War II with the production of arsenic ore from the U.S. mine. The district also produced tungsten used in electric filaments and as a strengthening agent in steel during and after World War II. Most of the tungsten production came from the Reaper, Lucy L, and Yellow Hammer mines.

The Gold Hill (Clifton) mining district lies near the Nevada state line, 40 mi south of Wendover in west-central Tooele County. Gold Hill is a large As-Au-Ag-Pb-Cu district and is the largest As and W producing district in Utah. Gold Hill’s production peaked during World War I immediately after the arrival of a railroad from Wendover. Total district metal production at modern metal prices is estimated at $111 million. The two largest producers in the district are believed to be the Gold Hill (Western Utah) and U.S. arsenic mines.
The Gold Hill district lies on the north end of the Deep Creek Range in the Basin and Range Province of west-central Utah. The Gold Hill district is structurally very complex and hosts at least three ages of mineralization: Jurassic, Eocene, and Miocene. The district also hosts an unusual suite of ore deposits including polymetallic pipe, skarn, vein, and replacement deposits. Most of the Gold Hill ore deposits are associated with a large (22 sq mi) Jurassic granodiorite plug (about 152 Ma). The polymetallic pipes are small, irregular, W-Cu-Mo-bearing chimneys of very coarse grained actinolite-tourmaline-orthoclase formed within the Jurassic granodiorite (e.g., Yellow Hammer mine). The skarns (Cu-W-As-Mo-Pb-Zn-Bi-Sb-Au) form in carbonate rock adjacent to the granodiorite stock and occur as prograde garnet-diopside and retrograde hornblende-actinolite-tourmaline skarns. These skarns include several small Au skarns like the Midas and Cane Springs orebodies (USGS Model 18f). The largest historical producers in the district are the arsenopyrite polymetallic vein and replacement deposits (Gold Hill and U.S. mines) formed in the Mississippian Ochre Mountain Limestone near the Jurassic granodiorite. These bodies (As-Pb-Cu-Zn-Sb) lie just outboard of the skarns and are controlled by the intersection of mineralizing fissures and favorable host beds (Nolan, 1935). Later mineralizing events in the Gold Hill district include W skarns associated with the Eocene (about 42 Ma) quartz monzonite plug (4 sq mi) north of Gold Hill at the Stardust and Timm mines (USGS Model 14a) and Miocene (~8 Ma) low-sulfidation Au quartz-adularia veins (USGS Model 25c) reported in Rodenhouse Wash at the Kiewit mine (Robinson, 2006).
Small sedimentary rock-hosted Au-Ag prospects (USGS Model 19c) occur at Ochre Springs and Trail Gulch in the west and northwestern portion of the Gold Hill district. The mineralization is reportedly hosted in siltstone/limestone at the contact between the Mississippian Ochre Mountain Formation and Chainman Shale.
The Jurassic-age mineralization in the Gold Hill mining district is primarily low-oxidation-state arsenopyrite replacement deposits and low-sulfidation-state W-Cu-Mo breccia pipe orebodies. These deposits suggest that Jurassic magmatism generated reduced, low-sulfide mineralizing fluids.