Makushin Valley

The Makushin Valley is a gold and silver 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: Makushin Valley

Commodity

Primary: Gold
Primary: Silver
Secondary: Arsenic
Secondary: Mercury

Location

State: Alaska
District: Aleutians

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: Epithermal vein, generic

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Wall rocks are propylitically altered volcaniclastic rocks that show no wall-rock alteration as a result of veining. Propylitic alteration is thought to predate mineralization and is probably not associated with quartz veining and gold mineralization.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Gold
Ore: Pyrite
Gangue: Chlorite
Gangue: Epidote
Gangue: Quartz

Comments

Comment (Workings): Workings / Exploration = Extensive sampling and mapping by Kennecott-Alaska in 1985 (Simpson, 1986) and BMEC in 1990 (Randolph, 1991). Veins along the ridge contained anomalous gold and silver but were too widely spaced and discontinuous to be of interest (Simpson, 1986). Gold grades derived from chip samples across the Makushin Vein system range up to 0.48 ox/t (16 ppm) and 3.12 oz/ton (107 ppm) silver, although Simpson (1986) reported 0.1 to 1.0 ppm gold is more typical. The zone having visible sulfides and gold yielded one sample of 8.575 oz/t (294 ppm) gold and 85.87 oz/t (2,944 ppm) silver (Simpson, 1986). Fluid inclusion studies suggest a formation temperature of 230 to 250xC; however, the system apparently did not undergo boiling (Randolph, 1991). BMEC sampling indicated NW-SE trend yields gold values consistently below 500 ppb while E-W trend ranged from 570 ppb to 3.34 oz/t (115 ppm). Arsenic and mercury values are high, whereas base metal values are low.

Comment (Exploration): Status = Inactive

Comment (Geology): Age = Late Tertiary or younger

Comment (Reference): Primary Reference = Randolph, 1991

Comment (Reserve-Resource): Reserves = Based on a body 450 by 60 by 2m, reserves of 110,000 tons suggested by Simpson (1986). No grade given.

Comment (Deposit): Model Name = Epithermal gold vein

Comment (Geology): Geologic Description = Propylitically altered prophyritic andesite and andesitic volcaniclastic rocks of the Unalaska Formation (see Drewes and others, 1961) contain quartz veins ranging from 1 inch (3 cm) to 2 feet (60 cm) in thickness. The veins are erratic (in distribution?) and discontinuous and trend N 50-60x W (Simpson, 1986). Quartz veins are exposed on the ridge abd in the "Makushin Vein" at 1,500' (450 m) elevation and in steep slopes on the north side of the valley. These veins consist of milky white quartz, trace pyrite and anomalous gold and silver. The lower elevation 'Makushin Vein' ranges between 4 and 7 feet (1.2 and 2.1 m) thick and is traceable for 1,200 feet (360 m). It trends N 70x W and dips steeply to the southwest. The Makushin Vein is composed of quartz that varies from gray to white and except for one observed 3 inch (8 cm) wide sulfide and visible gold-bearing zone, is sulfide free. The sulfide-bearing zone is located in approximately the center of the vein and contains very fine-grained sulfides and gold (0.1 mm) in a matrix of chlorite and epidote (Simpson, 1986). Later work by Battle Mountain Exploration Co. found the Makushin Vein bifurcates into two main structural trends running E-W and NW-SE. East-west trending veins are composed of massive, milky quartz that has been brecciated and then healed by multiple void-filling bands of cockscomb quartz. Northwest-southeast trending 'veins' generally have dense zones of quartz 'crackle-breccia.' Other nearby veins were examined by BMEC and typically were moderately anomalous in gold.

References

Reference (Deposit): Simpson, D.F., 1986, Aleutian Islands project, 1985 final report: Kennecott Alaska Exploration Company, 54 p. (Report held by the Aleut Native Corporation, Anchorage, Alaska.)

Reference (Deposit): Drewes, Harold, Fraser, G.D., Snyder, G.L., and Barnett, H.F., Jr., 1961, Geology of Unalaska Island and adjacent insular shelf, Aleutian Islands, Alaska: U.S. Geological Survey Bulletin 1028-S, p. 583-676.

Reference (Deposit): Randolph, D.B., 1991, Unalaska project, 1990 final report: Battle Mountain Exploration Company, Alaska District, 62 p., 5 appendices, 15 plates, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

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