Alpha Ridge

The Alpha Ridge is a gold 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: Alpha Ridge

Commodity

Primary: Gold
Secondary: Silver
Secondary: Lead
Secondary: Antimony
Secondary: Arsenic
Secondary: Zinc

Location

State: Alaska
District: Nome

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: Low-sulfide Au-quartz vein

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Albitization associated with the introduction of arsenopyrite and other metallic minerals in schist.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Stibnite
Ore: Sphalerite
Ore: Gold
Ore: Galena
Ore: Arsenopyrite
Gangue: Quartz
Gangue: Ankerite
Gangue: Albite

Comments

Comment (Exploration): Status = Probably inactive

Comment (Geology): Age = Mid-Cretaceous; postdates regional metmorphism and may be similar in age to low-sulfide Au-quartz veins of the Nome district (see, for example, the Divide prospect, NM058).

Comment (Deposit): Model Name = Low-sulfide Au-quartz veins ? (Cox and Singer, 1986; model 36a).

Comment (Reference): Primary Reference = This report

Comment (Workings): Workings / Exploration = About 1000 feet of trenches was excavated in 1991. An extensive soil geochemistry survey, part of a grid that extended from Monument Creek to Bangor Creek, was also completed between 1991 and 1993 by Kennecott Exploration Company. The prospect was probably originally located before 1920.

Comment (Geology): Geologic Description = The Alpha Ridge prospect is an old prospect but its location was first reported by Sainsbury and others (1972 [OFR 72-321]). It was explored by Kennecott Exploration Company from 1990 to 1993. A series of soil samples collected in a reconnaissance survey were anomalous in arsenic, gold, and other elements. The reconnaissance survey was followed up with a detailed soil geochemical survey and trenching; about 1,000 feet of trenches were excavated with a trackhoe. Mineralization at the site is associated with highly albitized, arsenic-rich rocks and with massive quartz veins; the mineralization appears to be crudely stratabound (C.C. Hawley, Cindy Buxton, and D.L. Olson, written communication, 1992). The most intense mineralization is in an area about 300 by 300 feet on the crest of the ridge immediately below a saddle at an elevation of 1,040 feet. This saddle coincides with a high-angle fault of nearly east-west strike. To the east this fault trends toward the head of the placer gold deposit on Alpha Creek (NM196) in the Nome C-1 quadrangle. Maximum gold content found in the trench samples was 2,200 ppb; numerous samples contained more than 500 ppb gold and more than 10,000 ppm arsenic. Lead and zinc are also locally strongly enriched. The highest lead and zinc contents are associated with a massive, west-northwest-striking quartz vein that is exposed in a trench and in rubble about 300 feet north of the fault-controlled saddle. Lead values in galena and possibly as an oxidized mineral, are as high as 5,000 ppm in rock samples. Zinc, inferred to originally have been in sphalerite, is as high as 580 ppm. Antimony is consistently anomalous in the trench samples. The highest antimony value, 370 ppm, coincides with a gold value of 2,900 ppb. Although the main area of mineralization is below the strong fault which underlies the saddle at the south end of the prospect, areas of albitized rock with quartz float exist at least 1,000 feet north of the area of most intense mineralization. Grab samples from outlying areas locally contain more than 9,000 ppb gold. The auriferous area on Alpha Ridge almost certainly contributed placer gold to Sledge Creek (NM169), as well as to the Alpha Creek placer (NM196) in the Nome C-1 quadrangle. The prospect is near the crest of a major antiform, and country rock is the calcareous metaturbidite schist unit of Bundtzen and others (1994).

References

Reference (Deposit): Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.

Reference (Deposit): Sainsbury, C.L., Hudson, T.L., Ewing, Rodney, and Marsh, W.R., 1972, Reconnaissance geologic map of the Nome C-2 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-321, 13 p., 1 sheet, scale 1:63,360.

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