Rosebud Mining District, Grouse Creek Mts (Grouse Creek Range), Box Elder County, Utah, USAi

Regional Level Types
Rosebud Mining District	Mining District
Grouse Creek Mts (Grouse Creek Range)	Mountain Range
Box Elder County	County
Utah	State
USA	Country

The Rosebud mining district covers a large area in the southern Grouse Creek Mountains of west-central Box Elder County. Rosebud is a small W district in terms of production but is nonetheless the third largest WO3 producer in Utah. The peak production occurred during high W prices in 1940–44 and 1954–56. Rosebud also may have produced a minor, unrecorded amount of Ag-Pb-Zn replacement ore (Doelling, 1980). Total district metal production at modern metal prices is estimated at $840,000. The Lone Pine W mine is the largest producer.
The Rosebud district is structurally complex and lies on the southwest side of the Albion–Raft River–Grouse Creek metamorphic core complex of the Basin and Range Province. Rosebud is underlain by upper Paleozoic sedimentary strata intruded and domed by three large (total about 11 sq mi) Eocene-age quartz diorite to quartz monzonite plutons collectively known as the Immigrant Pass plutonic complex. These stocks become increasingly felsic and larger over time so that the smaller, older southwestern phase is granodiorite and the larger, younger eastern phase is principally coarse-grained biotite granite. Doelling (1980) suggests that the Grouse Creek Mountains have been rotated westward by Basin and Range extension.
The Immigrant Pass plugs are locally surrounded by narrow garnet skarns, followed by tremolite-wollastonite, and finally broader zones of marblization and bleaching up to 1000 ft wide. Both the alteration and mineralization associated with the southwestern granodiorite stock is the strongest. The granodiorite adjoining the W orebodies is commonly propylitically altered to chlorite and epidote near the carbonate contact. The W mineralization typically occurs as 2- to 6-ft-thick, dark green, garnet- epidote-quartz skarns (USGS Model 14a) developed in the host carbonates. In addition to scheelite, the other primary minerals reported with the W ore include actinolite, barite, chlorite, diopside, galena, powellite, stolzite, vanadinite, and wulfenite (Meyer, 1981). The Lone Pine W underground mine is developed in a Devonian Guilmette Formation xenolith near the west side of the western intrusive and is the largest producer in the district, accounting for approximately 75% of the district’s total W production. Vanadium and Mo are also reported from this skarn. The A&W W skarn is another known producer. In addition to the W skarn deposits, Meyer (1981) reported scheelite and powellite disseminated over a wide area within the stock and quartzite near the Rocky Pass W underground mine.
Scattered, small shows of Pb-Zn-Ag mineralization lie outboard of the bleached and marbleized carbonate rocks. These prospects lie at a distance ranging from several hundred feet to a couple of miles from the Immigrant Pass plutons. These prospects include the Silver Riddle (Ag-Cu-Pb) and Mogul (Pb-Ag-Au) mines north of the Immigrant Pass plutonic complex (Doelling, 1980). The Silver Riddle mine reportedly has exceptionally high Ag values.