Step Mountain

The Step Mountain is a lead and zinc mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Step Mountain
Secondary: Wk

Commodity

Primary: Lead
Primary: Zinc
Secondary: Cadmium
Secondary: Silver

Location

State: Alaska
District: Black

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Mississippi Valley, Appalachian Zn

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Smithsonite
Ore: Hydrozincite
Ore: Galena
Gangue: Quartz
Gangue: Calcite

Comments

Comment (Geology): Geologic Description = 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).

Comment (Reserve-Resource): 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).

Comment (Workings): Workings / Exploration = The prospects have been examined since the late 1970s, and several short trenches and some diamond drilling have been completed (Northstar Exploration, Inc., 1999).

Comment (Deposit): Model Name = Carbonate-hosted Zn-Pb (Schmidt, 1997; Cox and Singer, 1986; model 32b)

Comment (Reference): Primary Reference = Northstar Exploration, 1999

Comment (Exploration): Status = Active

Comment (Deposit): Other Comments = These prospects lie on Doyon, Limited selected or conveyed land. For more information, contact Doyon, Limited.

Comment (Geology): Age = Permian or younger.

References

Reference (Deposit): Doyon, Limited, 1986, Mines, prospects, and geochemical anomalies on Doyon, Limited, regional overselection lands, Alaska: Fairbanks, Alaska, Doyon, Limited, Report 86-01A, v. 1, 150 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)

Reference (Deposit): Schmidt, J.M., 1997, Shale-hosted Zn-Pb-Ag and barite deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska, 1997: Economic Geology Monograph 9, p. 35-65.

Reference (Deposit): Mosher, Greg, 1990, Step Mountain project, Geological exploration and diamond drilling, 1990: Pasminco Exploration Ltd. for Doyon, Limited, unpublished report 92-77, 19 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)

Reference (Deposit): Underwood, M.B., Brocculeri, T., Bergfeld, D., Howell, D.G., and Pawlewicz, M., 1992, Statistical comparison between illite crystallinity and vitrinite reflectance, Kandik region of east-central Alaska: U.S. Geological Survey Bulletin 2041, p. 222-237.

Reference (Deposit): Northstar Exploration, Inc., 1999, 1998 Annual Report Kandik, Block 7: Fairbanks, Alaska. (Report held by Doyon, Limited, Fairbanks, Alaska.)

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