An overview of the mineral deposits of the Red Mountain mining district, San Juan Mountains, Colorado
D.A. Gonzales and R.A. Larson
The Red Mountain mining district in Ouray County represents one of the oldest and most famous districts in the western San Juan Mountains. Deposit types in the Red Mountain district include breccia pipes with ore chimneys that extend to depths of 1000 ft (~300 m) along the ring fractures of the Silverton caldera. These deposits formed by expulsion of acidic hydrothermal fluids in proximity to hypabyssal plutons causing extensive advanced argillic to argillic alteration in adjacent country rocks. Discontinuous shoots of ore define a crude zonation within these deposits that grade from Ag-Pb-Zn in the upper levels to Cu-Au in the lower zones. These high-grade breccia pipe deposits were initially explored and mined from 1874 to 1910 yielding immense production of precious (Au, Ag) and base metals (Pb, Zn, Cu), that provided incredible wealth. To the west and northwest of the Red Mountain breccia pipes, numerous fissures and veins formed in radial fractures that fan outward from the structural walls of the Silverton caldera. These high-grade veins were the focus of some of the most notable base and precious metal deposits in the region, such as the Idarado mine (including the Smuggler-Union, Black Bear, Argentine), the Camp Bird mine, and the Revenue-Virginius mine. Veins in this system sometimes extended for several kilometers on strike and hundreds of meters in depth, and were extensively mined from 1874 to the 1980’s. Base metals dominated the veins at depth with increasing concentrations of gold at higher levels. The deposits in the Red Mountain mining district define a unique period of geologic history marked by widespread mineralization related to middle to late Cenozoic magmatism. The mining in this district also left an indelible mark on the human history of the area. Current mining at the Revenue-Virginius, just to the northwest of this district, marks the latest chapter in the history of mining in the area.
- Gonzales, D.A.; Larson, R.A., 2017, An overview of the mineral deposits of the Red Mountain mining district, San Juan Mountains, Colorado, in: The Geology of the Ouray-Silverton Area, Karlstrom, Karl E.; Gonzales, David A.; Zimmerer, Matthew J.; Heizler, Matthew; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 68th Field Conference, pp. 133-140.