Park Valley Mining District, Raft River Mountains, Box Elder County, Utah, USAi

Regional Level Types
Park Valley Mining District	Mining District
Raft River Mountains	Mountain Range
Box Elder County	County
Utah	State
USA	Country

The Park Valley (Golden, Century Hollow) mining district lies on the south flank of the Raft River Mountains about 70 mi west- northwest of Tremonton in north-central Box Elder County. Park Valley is a modest Au district. The district began production in the late 1890s and continued to be a small but steady Au producer well into the 1910s (Butler and others, 1920). There was a revival of activity in the district with the devaluation of the U.S. dollar during the depths of the Great Depression in 1934 and the consequent escalation of the Au price from $20.67 to $35 per oz. Some of the more refractory and lower grade (?) sulfide ores may have been processed at this time. Total district metal production at modern metal prices is estimated at $18 million. The last recorded production from Park Valley was in 1946 and the estimated total production is 16,409 ounces of Au along with minor Ag, Pb, and Cu.
The Park Valley area is geologically complex, being on the south flank of the Albion–Raft River–Grouse Creek metamorphic core complex. The mines developed narrow, high-grade Au quartz veins primarily hosted in Neoarchean Green Creek Complex quartz monzonite gneiss (the oldest intrusive rock in Utah) and lesser schist. The Green Creek Complex is unconformably overlain by the Neoproterozoic Elba Quartzite which dips moderately, about 10° to 35°, to the south. The age of mineralization has not been documented, but ore does not seem to extend up into the Elba Quartzite.
The known Au mineralization in the district is focused in the Corner Creek–Suzanna Canyon–Century Hollow area but extends eastward into Twin Canyon (Great Buffalo mine), Big Hollow, and possibly even Pine Creek canyons. The Century underground mine is the largest producer and the Suzannah underground mine, the second largest producer, potentially lies on the southwestern extension of the same vein set. These veins extend for a distance of at least a couple of thousand feet trending about N. 20° E. and have a moderate to steep southeast dip. Some of the ore shoots plunge southeasterly within the plane of the vein. Two types of veins are recognized: (1) barren, coarse quartz ±orthoclase veins and (2) mineralized, green-gray, fine- grained, quartz-sulfide veins. The ore zone ranges from several inches to a few feet thick and the primary ore/sulfide minerals include galena, sphalerite, chalcopyrite, arsenopyrite, and pyrite (Butler and others, 1920). Panning of the ore zone yields visible native gold. The historical ore grades run from about 5 to 15 ppm Au and 50 to 200 ppm Ag. Gold grades reportedly increase with the Pb (1% to 10% Pb) content. The deposits have been mostly worked out to the water table (Perry and McCarthy, 1977).
All known mineralization in the Park Valley district is on private land.