Mineral Mountain Mining District, Washington County, Utah, USAi

Regional Level Types
Mineral Mountain Mining District	Mountain
Washington County	County
Utah	State
USA	Country

The Mineral Mountain district is in remote northwestern Washington County about 32 mi northwest of St. George. The area has no reported production.
The Mineral Mountain district is in the Basin and Range Province. The district is considered to be the southwesternmost intrusion of the Miocene-age Iron Axis; however, its stock is 8 to 10 million years younger and much more felsic than the other intrusions on this belt to the northeast.
The alteration/mineralization in the district is centered on the Mineral Mountain stock. The stock (about 12.1 Ma) is a high- silica granite porphyry made up of mostly fine-grained orthoclase and contains abundant, large beta quartz phenocrysts. The stock is cut in half by a west-northwest-trending, right-lateral strike-slip fault and the north half is displaced approximately 7800 ft to the east. A small (600-ft-diameter) alaskite plug intrudes the northern Mineral Mountain stock on the southwest flank of Mineral Mountain, and lamprophyre (kersantite) dikes are noted near some of the mineralization (Morris, 1980).
The Mineral Mountain stock domes and intrudes Pennsylvanian Callville Limestone and overlying Miocene volcanic rocks. Small magnetite-Cu ±Au ±Ag ±Mo vein/replacement deposits are present adjacent to the stock. Anomalous Mo (310 ppm) and weakly anomalous W (25 ppm) are present in a dump sample at the Humbug (Pickadilly) mine on the west side of the stock (Morris, 1980). In addition to narrow brucite-serpentine skarns and more widespread marblization of the carbonate rocks adjoining the stock, the overlying volcanic rocks are locally argillized, silicified, and/or pyritized (Morris, 1980; Eppinger and others, 1990). Morris (1980) also notes that narrow quartz veins with silicified selvages cut the north margin of the granite on Marble Mountain. The 25-foot-wide Beauty Knoll alunite vein cuts andesitic volcanic rocks along a northwest trend for 1500 ft about a mile northeast of the stock.
Minor Zn-Pb mineralization is located 0.6 to 1.5 mi to the southeast of the Mineral Mountain granite. About 2 mi due south of the stock, the Treasure Chest sedimentary rock-hosted Au-Ag prospect (USGS Model 19c) occurs along the unconformity between the Callville Limestone and the overlying Paleocene to Eocene lower Claron Formation. The lower Claron Formation is a light-yellow-gray to red conglomerate. This contact is the same as the mineralized contact in the Goldstrike district about 3 mi to the southeast.