The Medicine Bow Mountains and Sierra Madre are Precambrian-cored Laramide uplifts that straddle the margin of the Wyoming craton. The Wyoming craton was established more than approximately 2.7 billion years ago (2.7 Ga, or Giga-annum), but was later affected by a regional metamorphic event 1.9–1.7 Ga. The south boundary of the Wyoming Craton in the Medicine Bow Mountains and Sierra Madre terminates against the Mullen Creek-Nash Fork shear zone. This shear zone, which forms part of the Cheyenne belt suture, represents a continental-arc collision zone separating the Wyoming Province to the north from cratonized (1.7 Ga) Proterozoic basement of the Colorado Province to the south.

Within the Colorado Province south of the Cheyenne belt, metavolcanic and metasedimentary rocks provide excellent hosts for magmatic massive sulfide mineralization (copper, zinc, lead, silver, gold) and some shear zone copper, gold, and associated gold placers. Layered mafic-ultramafic intrusives, ultramafic massifs, and fragments with platinum, palladium, gold, silver, copper, titanium, chromium, and vanadium anomalies occur within the Proterozoic terrain – most notable are the Mullen Creek, Lake Owen, and Puzzler Hill complexes. The New Rambler mine is located along the northeastern edge of the Mullen Creek mafic-ultramafic complex in the Medicine Bow Mountains and is Wyoming’s only mine known to have historically produced platinum and palladium. The mineralization, occurring in hydrothermally altered mafic shear-zone cataclastics, may have been remobilized from the layered complex. Because of their high potential for platinum-palladium mineralization, Mullen Creek, Lake Owen to the east, and Puzzler Hill in the Sierra Madre continue to be platinum exploration targets.

The Douglas Creek district in the central Medicine Bow Mountains includes all placer deposits along Douglas Creek and its tributaries, from Rob Roy Reservoir southward for 6 miles to below Lake Creek. Gold was discovered in Moore’s Gulch, a tributary of Douglas Creek, by Iram Moore in 1868. Lode gold discoveries in both the New Rambler and Keystone districts resulted from placer gold being traced upstream to its primary sources. Heavy placer activity along the creek included elaborate hydraulic ditches in use by 1876. Resurgent placer activities during the 1930s, 1940s, and 1950s used gasoline-powered draglines and floating washing plants. Gold recovered from gravels up to 20 feet thick varied from 890 to 960 fine, with some silver and traces of platinum. Currey (1965) estimated total gold production from the Douglas Creek placers at about 4,000 ounces. The Douglas Creek district remains a popular area for amateur placer mining.

Thick successions of Late Proterozoic metasediments that overlie the Archean basement characterize the northern part of the district, where mineralization is typified by copper-bearing quartzites, pegmatites, quartz veins, and unaniferous metaconglomerate. Middle Proterozoic calc-alkaline metavolcanics intruded by granitic plutons characterize the southern part of the district, where rocks host stratiform volcanogenic sulfides and related mineralization. Fracture-controlled, copper-dominated base metal deposits typify mineralization within the shear zone.

The Ferris-Haggarty mine in the central Sierra Madre was one of the world’s more important copper deposits during the early 1900s. This significant deposit with accessory gold and some silver was developed in a sheared metaconglomerate. The mine produced an estimated 21 million pounds of copper with some byproduct gold and silver. A 1988 estimate of unmined ore included 928,500 tons of 6.5 percent copper containing 116,800 ounces of gold. Current high metals prices have sparked re-evaluation and exploration of the Ferris-Haggarty and adjacent areas.

Amateur prospectors still search the Sierra Madre for gold although it was always secondary to copper in the Encampment district.