Yost Mining District, Box Elder County, Utah, USAi

Regional Level Types
Yost Mining District	Mining District
Box Elder County	County
Utah	State
USA	Country

The Yost mining district lies on the north flank of the western Raft River Mountains in northwestern Box Elder County about 83 mi west-northwest of Brigham City. The district has no official recorded production, but Doelling (1980) reported that the mine workings suggest that a very small volume of Pb-Ag and possibly some W ore may have been produced.
The district hosts two primary styles of mineralization: rusty quartz veins and distal disseminated Ag-Au deposits similar to Black Pine, Idaho. The Jones Creek distal disseminated Ag-Au occurrence (USGS model 26a) is located on the north flank of the central Raft River Mountains about 2.5 mi south of the Idaho state line and 5.7 mi east of the village of Yost. The property was initially discovered by the Battle Mountain Exploration Company while doing Au reconnaissance in the region of the Black Pine carbonate-hosted Au mine, 21 mi to the east-northeast in Idaho. Battle Mountain acquired the Jones Creek property in 1988, drilled about a dozen shallow (less than 400 ft deep) vertical holes in 1990–91, and calculated a subeconomic inferred resource of approximately 1 million tons averaging about 0.68 ppm Au (totaling about 20,000 ounces Au). Battle Mountain dropped the property in 1991. The Jones Creek deposit is associated with a small, detached, erosional remnant of Ordovician Pogonip Group limestone sitting on a low ridge of Neoproterozoic Elba Quartzite. Oxide mineralization, greater than 0.45 ppm Au, occurs at the surface in both the limestone and underlying quartzite in an area a few hundred ft in diameter and about 100 ft thick. Mineralization has subequal Au and Ag having strong As (>500 ppm) and little else. Since Au occurs in both the upper and lower plate rocks, mineralization is presumed to be post-detachment, potentially middle Miocene (Krahulec, 2011).
The rusty W-bearing quartz veins may be metamorphogenic and are primarily hosted in Neoproterozoic mica schist and quartzite and Cambrian rocks. The veins locally have some fresh pyrite, galena, molybdenite, and scheelite (Doelling, 1980). A particularly strong set of northeast-trending veins is found at the George Creek W mine. These veins are readily mappable from aerial photography and occur in the schist member of the Neoproterozoic Elba Quartzite in the George Creek drainage (SE1⁄4 section 20, T. 14 N., R. 14 W.).
Several adits and shafts scattered in the Johnson Creek drainage south of Yost are also associated with low-angle detachment faulting. The mineralization here is primarily argentiferous galena with weak Au values along shear zones in the metamorphosed Paleozoic section, principally the Pogonip Group carbonates (Doelling, 1980).