Tarn

The Tarn is a gold and copper 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: Tarn

Commodity

Primary: Gold
Primary: Copper
Secondary: Antimony
Secondary: Arsenic

Location

State: Alaska
District: McGrath

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: Porphyry Cu-Au

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Biotite in hornfels; ankerite in intrusions.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Chalcopyrite
Ore: Arsenopyrite
Gangue: Tourmaline
Gangue: Quartz

Comments

Comment (Exploration): Status = Inactive

Comment (Workings): Workings / Exploration = Regional exploration work conducted by WGM Inc. in the late 1970s discovered the Tarn and related prospects in the Mystery Mountains (Andrews, 1978). From 1988 to 1990, American Copper and Nickel Company conducted regional exploration, which included a detailed airborne geophysical survey. ASA Inc. continued detailed exploration work from 1991 to 1997 (DiMarchi and others, 1997). No drilling has taken place on the property, and no assay data was found for this summary.

Comment (Deposit): Model Name = Porphyry Cu-Au (Cox and Singer, 1986; model no. 20c)

Comment (Deposit): Other Comments = See Copenhagen Hill (MD030), Frozen Creek (MD032), Pork Chop (MD031), and Mystery Mountains West (MD029) prospects.

Comment (Geology): Age = the Tarn prospect is inferred to be Late Cretaceous, based on isotopic ages of plutonic rocks in Mystery Mountains (Moll and others, 1981).

Comment (Reference): Primary Reference = DiMarchi and others, 1997

Comment (Geology): Geologic Description = The Tarn prospect is within the eastern part of a northeast trending belt of porphyry-like copper-gold prospects that strike for 7 miles (11 km) in the central Mystery Mountains. The Tarn prospect consists of hydrothermal breccias in monzonitic dikes and small stocks that contain chalcopyrite, pyrite, tourmaline, and minor to trace arsenopyrite. Malichite occurs in hairline fractures in intrusive rocks; alteration and mineralization is not well developed in country-rock hornfels. The Tarn prospect is inferred to be Late Cretaceous, based on isotopic ages of plutonic rocks in Mystery Mountains (Moll and others, 1981). No assay data was found for this summary.

References

Reference (Deposit): DiMarchi, J.J., and Frantz, P.S., 1997, Annual Report for 1997-Doyon Option Lands, Block 10: ASA Inc.-Montague Gold Joint Venture Report, Volume II: Unpublished report, 189 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)

Reference (Deposit): Moll, E.J., Silberman, M.L., and Patton, W.W. Jr., 1981, Chemistry, mineralogy, and K-Ar ages of igneous and metamorphic rocks of the Medfra quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-811C, 15 p., 2 sheets, scale 1:250,000.

Reference (Deposit): Andrews, Tom, 1978, Summary of Progress, Doyon Project, Mystery Mountains, (Block 10): Anchorage, Alaska, WGM Inc., 24 pages (Held by Doyon Ltd., as proprietary report 78-42).

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