Gold Hill Mining District: record SW5360b

Region	West, Southwest
States	Utah
Mineral systems	Porphyry Cu-Mo-Au
Deposit types	Distal disseminated silver-gold Polymetallic sulfide S-R-V-IS Porphyry/skarn copper S-R-V tungsten
Commodities	copper gold lead molybdenum silver uranium
Critical minerals	arsenic bismuth tungsten zinc
Other minerals	antimony arsenic bismuth cobalt gallium germanium indium manganese PGE rhenium scandium tellurium tungsten zinc

Information leading to the delineation of this focus area

Basis for focus area	Tungsten skarns (for example, Lucy L mine); disseminated gold (for example, Trail Gulch prospect); polymetallic intrusion-related, vein, replacement, and skarn (for example, Yellow Hammer, Rube, Gold Hill mines); copper skarn (for example, Copperopolis mine). Gold Hill mining district boundary from Krahulec (2018b).
Identified resources	Historical production of arsenic, bismuth, copper, gold, lead, molybdenum, silver, tungsten, and zinc; current production of gold.
Production	Production era depends on the commodity; production in the area peaked during WWII, including arsenic from the U.S. Mine and Gold Hill mines; bismuth from the Wilson Consolidated mine; tungsten from multiple mines, including Reaper, Lucy L, Fraction, Stardust, and Yellow Hammer mines. Zinc from multiple mines, including Garrison and Cyclone mines. Gold Hill is the largest historical producer of As and W in Utah, with 25,000 oz Au 832,000 oz Ag, 1,700 st Cu (Robinson, 2006), and 100,00 t As (El-Shatoury and Whelan, 1970). Production quantities of Bi, Mo, Pb and Zn are unknown.
Status	Past mining. Currently minor gold production; minor tungsten production in 2016 (~275 tons of ore).
Estimated resources	No formal estimates are known.
Geologic maps	Robinson (1993), scale 1:24,000; Nolan (1935, plates 1 and 2), scale 1:62,500 and 1:24,000, respectively.
Geophysical data	Inadequate Rank 4 aeromagnetic and Rank 5 aeroradiometric coverage.
Favorable rocks and structures	Polymetallic pipes and skarn in Jurassic granodiorite; skarns, polymetallic veins, and replacement deposits in the Mississippian Ochre Mountain Limestone and Pennsylvanian Ely Limestone associated with Jurassic and Eocene intrusions; late Oligocene/early Miocene high silica rhyolite dikes evidence for concealed Climax type Mo porphyry; late Miocene low-sulfidation Au quartz-adularia veins with Be and disseminated Au in Jurassic granodiorite.
Deposits	Arsenic: U.S. Mine and Gold Hill mine (MRDS dep_id: 10021179); Bismuth: Wilson Consolidated mine (MRDS dep_id: 10098475); Tungsten: Reaper mine (MRDS dep_id: 10041737), Lucy L, Fraction, Stardust, Yellow Hammer mine (MRDS dep_id: 10098085); Lead and zinc: Garrison mines (MRDS dep_id: 10046163), Cyclone mine; Gold: Alvarado mine (MRDS dep_id: 10102140), Midas mine, Rube mine; Silver: Silver King and Climax mines; Molybdenum: Yellow Hammer mine (MRDS dep_id: 10098085).
Evidence from mineral occurrences	MRDS: UMOS (Utah Geological Survey, 2021).
Geochemical evidence	See Robinson (2006, 2016); Nolan (1935); Burwell (2018).
Geophysical evidence	Unknown.
Evidence from other sources	See Krahulec (2018b).
Comments	Gold Hill district is the largest W and As producer in Utah from skarn and replacement deposits associated with the Eocene (As, W) and Jurassic (W) intrusions in the area. The Gold Hill district is complex from a structural, igneous, and mineralization perspective (Robinson, 2006; Burwell, 2018; Krahulec, 2018b). Several igneous events are recorded in Gold Hill’s geology including a Jurassic granodiorite stock, an Eocene quartz monzonite stock, an Oligocene rhyolite porphyry dike swarm, and Miocene bimodal volcanic rocks. Multiple mineralizing events occurred at the Gold Hill district (Robinson, 2006; Krahulec, 2018b), and at least three ages of mineralization are recorded (Jurassic, Eocene, and Miocene). Late Oligocene Climax-type porphyry Mo potential related to the high silica rhyolite dikes is hypothesized and had limited drill testing in the late 1970s though no mineralization was intersected. Deposit types found at Gold Hill include skarns, polymetallic intrusion-related deposits, polymetallic veins and replacement deposits, disseminated gold deposits, and low sulfidation Be-enriched quartz-adularia veins. The Jurassic granodiorite/quartz monzonite is an oxidizing intrusion with reduced (pyrrhotite-bearing) mineral assemblages in several skarns. There is evidence for brine input creating an IOCG type metallogenic signature in some deposits. In addition to the produced critical minerals there is known Re enrichment associated with Mo mineralization at Yellow Hammer mine, Sb enrichment and barite occurrences with As mineralization at the U.S. Mine and Gold Hill mines, V enrichment at the New Baltimore mine, Sn enrichment and barite occurrences at the Silver Hill mine, and fluorite occurrences at the Gold Bond prospect (Utah Geological Survey, 2021).
Cover thickness and description	Variable.
Authors	Andrew Rupke, Stephanie Mills.
New data needs	Newmont flew an aeromagnetic survey over the district that the Utah Geological Survey is trying to secure as a donation.
Geologic mapping and modeling needs	Updated geologic mapping needed west and south of main deposit area-S. Mills and A. Rupke of Utah Geological Survey are mapping the Clifton quadrangle across the southern portion at 1:24,000 scale.
Geophysical survey and modeling needs	Possible need for high resolution geophysics.
Digital elevation data needs	Lidar inadequate.