West Tintic Mining District, West Tintic Mountains, Juab County, Utah, USAi

Regional Level Types
West Tintic Mining District	Mining District (Inactive)
West Tintic Mountains	Mountain Range
Juab County	County
Utah	State
USA	Country

The West Tintic mining district is in north-central Juab County 34 mi northwest of Nephi. The most notable production in the West Tintic district came from the Scotia mine, which produced about 3000 tons of high-grade Au-Ag-Pb ore (Butler and others, 1920), including several hundred tons of 2400 ppm Ag ore. However, West Tintic is also the second largest W producer in the state. Total district metal production at modern metal prices is estimated at $4.3 million.
The West Tintic district is geologically situated on the Deep Creek–Tintic mineral belt in the Basin and Range Province. The district is in a window of lower plate Paleozoic carbonate rocks overridden by Proterozoic rocks in the upper plate of the Sheeprock thrust. The lower plate Paleozoic strata generally strike northerly and dip very steeply to the east (Stringham, 1942). The range has been rotated eastward an indeterminate, but possibly significant, amount (25°–35°) by post-mineral, listric, extensional faulting. This resulted in deeper levels of the intrusive-hydrothermal system being exposed on the west side of the district and progressively shallower levels of the system exposed to the east.
Mineralization at West Tintic is zoned from: (1) weak porphyry Cu-Mo mineralization in the southwest (USGS Model 17), to (2) W-Cu-Fe skarns adjacent to the Tertiary monzonite stocks (USGS Model 14a), to (3) Pb-Zn replacement deposits in Paleozoic-age carbonate rocks (USGS Model 19a), to (4) minor Au occurrences along the Sheeprock thrust to the north and east. The exposed Little Bingham porphyry Cu-Mo-style mineralization occurs in a light gray, medium- to coarse-grained granite (~39 Ma) with coarse pink K-spar phenocrysts. Copper mineralization occurs as low-sulfide chalcopyrite veins and disseminations in weakly altered granite. The mafic minerals are destroyed, but K-spar is generally stable. Copper grades are low, probably averaging about 0.1% Cu, but the deposit appears to be open under cover to the east and south.
The discovery outcrop at the Scotia mine was in a thrust sliver of Precambrian phyllite that dipped about 60° N. The exact age and correlation of the remaining, deeper host strata are uncertain, but are tentatively interpreted as Silurian Laketown Dolomite (Stringham, 1942). Scotia mineralization occupies either northerly trending open fissures or east-northeasterly trending, steeply north-dipping quartz-sulfide veins and associated small blanket replacement bodies. These Ag-Au-Pb replacement deposits occur as irregular, gentle northeast-dipping, easterly elongated pods along the subsidiary thrust faults and narrow aplite porphyry sills. The Scotia ores are nearly completely oxidized, but the primary minerals recognized include galena, arsenopyrite, pyrite, sphalerite, famatinite, and chalcopyrite in a gangue of a little quartz (Stringham, 1942).