Step Mountain; WK Prospects, Black Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Step Mountain; WK Prospects	Group of Prospects
Black Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

These prospects lie on Doyon, Limited selected or conveyed land. For more information, contact Doyon, Limited.
Location: The Step Mountain prospects cover about 5 square miles and are located in sections 7-9, 17, 18, and 20, T. 8 N., R. 31 E., of the Fairbanks Meridian, just to the north of Step Mountain. The coordinates are for the approximate center of the area. The location is accurate. These prospects are located within Doyon, Limited selected or conveyed land.
Geology: The Step Mountain Pb-Zn prospects are in a doubly plunging antiform that forms a dome-shaped mountain. The Permian Step Conglomerate and the Nation River Formation are exposed at its core. A northwest- or west-trending fault cuts the center of Step Mountain and may host additional mineralization (Northstar Exploration, Inc., 1999). The zinc minerals consist of smithsonite, a light gray to white oxide mineral that is not believed to be an alteration product of sulfides, and hydrozincite. The lead mineral is galena (Doyon, Limited, 1986). The lead and zinc minerals are in quartz veins(?) in Permian limestone breccia zones and lenses, in fossiliferous calcareous siltstone, and in layers overlying fossiliferous calcarenite, where it locally replaces coquina in an upper packstone unit (Mosher, 1990; Schmidt, 1997). Along the crest of the anticline, the conglomerate, sandstone, and cross-cutting quartz veins contain only slightly anomalous base-metal values (Northstar Exploration, Inc., 1999). Vitrinite reflectance data from the Devonian Nation River Formation and the Mississippian Ford Lake Shale in the Step Mountain antiform suggest that these rocks were exposed to temperatures of approximately 240 to 285 degrees Celsius (Underwood and others, 1992). There are an estimated 35,000 to 850,000 tons of economic grade Zn, which includes 4.9 meters of 2.7 percent Zn, 3.6 meters of 18.8 percent Zn, and 40 cm of 19.7 percent Zn (Northstar Exploration, Inc., 1999). This prospect was discovered in the late 1970s and has been explored by short trenches and diamond drilling (Northstar Exploration, Inc., 1999).
Workings: The prospects have been examined since the late 1970s, and several short trenches and some diamond drilling have been completed (Northstar Exploration, Inc., 1999).
Age: Permian or younger.
Reserves: There are an estimated 35,000 to 850,000 tons of economic grade Zn, which includes 4.9 meters of 2.7 percent Zn, 3.6 meters of 18.8 percent Zn, and 40 cm of 19.7 percent Zn (Mosher, 1990).

Commodities (Major) - Pb, Zn; (Minor) - Ag, Cd
Development Status: None
Deposit Model: Carbonate-hosted Zn-Pb (Schmidt, 1997; Cox and Singer, 1986; model 32b)

Other Databases

Link to USGS - Alaska:	CY030

Other Regions, Features and Areas containing this locality

References