Makushin Valley

Prospect in Alaska, United States with commodities Gold, Silver, Arsenic, Mercury

Geologic information

Identification information

Deposit ID 10003262
MRDS ID A106003
Record type Site
Current site name Makushin Valley

Geographic coordinates

Geographic coordinates: -166.66573, 53.923 (WGS84)
Relative position North side of Makushin River Valley, about 5,000 feet (1.5 km) inland from coast at Broad Bay. Prospect extends over a distance of about 1 km along and below ridge.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Silver Primary
Arsenic Secondary
Mercury Secondary

Materials information

Materials Type of material
Gold Ore
Pyrite Ore
Chlorite Gangue
Epidote Gangue
Quartz Gangue

Alteration

  • (Local) 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.

Mineral occurrence model information

Model code 105
USGS model code 25a-d
Deposit model name Epithermal vein, generic
Mark3 model number 119

Nearby scientific data

(1) -166.66573, 53.923

Comments on the geologic information

  • 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.
  • Age = Late Tertiary or younger

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Aleutians

Comments on the reserve resource information

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

Comments on the workings information

  • 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.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A106003
USGS Alaska Resource Data File ARDF UN009

Bibliographic references

  • 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.

  • 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.)

  • 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.)

Comments on the references

  • Primary Reference = Randolph, 1991

General comments

Subject category Comment text
Deposit Model Name = Epithermal gold vein

Reporter information

Type Date Name Affiliation Comment
Reporter 06-MAY-1996 F.H. Wilson U.S. Geological Survey