Pine Grove Mining District, Beaver County, Utah, USAi

Regional Level Types
Pine Grove Mining District	Mining District
Beaver County	County
Utah	State
USA	Country

The Pine Grove mining district lies in the Wah Wah Mountains of western Beaver County about 32 mi west of Milford. The mining district was historically a minor Zn-Pb-Ag producer (about $871,000 at modern metal prices), but substantial Mo exploration began in 1975 when Phelps Dodge Corporation drilled the first deep hole into porphyry Mo mineralization at a depth of 3300 ft. The Tasso (Wah Wah) underground mine is the largest producer.
Pine Grove lies in the Wah Wah Mountains of the eastern Basin and Range Province. The district hosts a giant, Climax- type porphyry Mo deposit related to a sub-volcanic, silicic-alkalic, high-silica rhyolite porphyry plug that intrudes a thick sequence (over 6000 ft) of Upper Proterozoic and Lower Cambrian quartzose clastic sedimentary rocks. The Pine Grove rhyolite porphyry (~24 Ma) is a steep-walled, oval-shaped plug covering about 0.4 sq mi at the surface. Molybdenum mineralization occurs mostly along the margins of the Pine Grove porphyry beginning at a depth of about 3000 ft (Staff, 1984; Keith and others, 1986; Stegen, 2016).
According to Keith and others (1993), the evidence that Pine Grove is a Climax-type porphyry Mo deposit includes: (1) multiple intrusions of high-silica rhyolite, (2) large tonnage of high-grade ore, (3) accessory fluorite, topaz, and huebnerite in the ore zone, (4) lack of appreciable Cu in the system, and (5) accessory monazite, xenotime, and ilmenorutile in the intrusive phases (USGS Model 16). The commonly published reserve figure for Pine Grove is about 125 million tons at 0.17% Mo at a minimum 300-foot width and a 0.12% Mo cutoff grade (Stegen, 2016). This reserve is contained within a much larger estimated geological mineral inventory of over 300 million tons at 0.17% Mo. No important mineral exploration or development has been done on the property since about 1983. Because porphyry Mo deposits tend to occur in clusters, there could be a potential for the discovery of additional Mo resources in the district (Keith and others, 1993).