Orange Mountain

Prospect in Alaska, United States with commodities Silver, Gold

Geologic information

Identification information

Deposit ID 10308138
Record type Site
Current site name Orange Mountain

Geographic coordinates

Geographic coordinates: -160.62341, 55.20823 (WGS84)
Relative position This prospect is on southeastern Unga Island approximately 4,000 feet southwest of Red Mountain (Wilson and others, 1988, locality 29). The map site is at an elevation of 1,060 feet, at the top of a hill marked by a large color anomaly. Orange Mountain is informally named for the color anomaly; it is not named on the topographic map. The location is accurate.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary

Materials information

Materials Type of material
Gold Ore
Pyrite Ore
Tetrahedrite Ore
Barite Gangue
Quartz Gangue

Alteration

  • (Local) The alteration consists of as pervasive argillization and pyritization of andesite tuffs and silicification of felsic tuffs.

Nearby scientific data

(1) -160.62341, 55.20823

Comments on the geologic information

  • Geologic Description = This prospect, marked by a 2.7-square-mile color anomaly, is the largest single area of alteration on Unga Island. It is in rocks mapped as the late Eocene to early Oligocene Popof volcanic rocks (Wilson and others, 1995). From 1979 to 1983, it was explored first by Resource Associates of Alaska and then by UNC Teton Exploration Drilling Company (Peterson and others, 1983). The prospect consists of a gently-dipping, interbedded sequence of silica-replaced felsic tuffs and argillically altered andesite tuffs and flows. The alteration extends over a vertical range of at least 500 feet (Ellis and Apel, 1990). Numerous shears, faults, fracture zones, and breccias result in structural complexities (Peterson and others, 1983). The silica-replaced tuffs contain 5 percent disseminated pyrite. They also contain veins, disseminations, and pods of barite, and veinlets and pods of quartz. In brecciated areas, the quartz and barite veins locally occur together, and some of the quartz is replaced by barite. The argillically altered andesite contains 25 percent pyrite as veinlets and disseminations. Tetrahedrite has also been reported. There is a positive correlation between precious metal values and the silicified rock; the highest values are associated with shears and breccias. The highest precious metal values obtained from surface samples were 2.85 ppm gold and 26 ppm silver; their mean value was 0.045 ppm gold and 0.4 ppm silver (Peterson and others, 1983). Detectable and weakly anomalous gold values occur in drill holes in sections 100 or more feet thick (115 feet in OM-2 and 370 feet in OM-3). The highest subsurface precious metal values were 0.41 ppm gold and 3.4 ppm silver. Mean values of base metals were at 40 ppm copper, 20 ppm lead, 20 ppm zinc, and 50 ppm arsenic. The entire area is enriched in mercury, and values of as much as 107 ppm of mercury occur in silicified tuffs. The mean mercury value is 1.6 ppm. Thallium, tellurium, antimony, and bismuth were also detected. In 1990 Battle Mountain Exploration Company mapped the site and collected approximately 117 rock chip samples. Their mapping indicated that the silicified rock forms a cap overlying argillically altered tuffs containing as much as 70 percent pyrite (Ellis and Apel, 1990). Gold values in quartz veins cutting the silicified tuffs ranged from 0.05 to 0.25 ppm.
  • Age = Eocene or younger.

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name Alaska Peninsula

Comments on the workings information

  • Workings / Exploration = During the period 1979 to 1983 Resource Associates of Alaska and UNC Teton Exploration Drilling Company conducted 8.5 miles of grid mapping, collected and analyzed 750 rock and soil samples, conducted 1.4 miles of VLF-EM survey, and drilled 3 core holes for a total of 2,453 feet. The highest metal values of surface samples were 2.85 ppm gold and 26 ppm silver. The mean values were 0.045 ppm gold and 0.4 ppm silver. The highest subsurface values were 0.41 ppm gold and 3.4 ppm silver. In 1990 Battle Mountain Exploration mapped the site in detail and collected approximately 150 rock samples. A cluster of low-level gold anomalies was outlined at the top of Orange Mountain. Individual quartz veinlets assayed 0.05 to 0.25 ppm gold.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF PM067

Bibliographic references

  • Deposit

    Peterson, R.J., Lemmers, J., Handverger, P., Gallagher, J., Pilcher, R., East, J., Macleod, T., Bartels. E., 1982, Geology and precious metals potential Unga, Popof, and Korovin Islands, Shumagin Group, Aleutian Chain, Alaska: UNC Teton Exploration Drilling Company report, 127 p., 5 map sheets, various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Peterson, R.J., Handverger, P., Rosenkrans, D., Bartels, E, and Woolston, D., 1983, Shumagin Islands precious metal exploration program southwest Alaska: UNC Teton Exploration Drilling Company report, 61 p. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Wilson, F.H., White, W.H., and DuBois, G.D., 1988, Brief descriptions of mines, prospects, and mineral occurrences in the Port Moller and Stepovak Bay quadrangles, Alaska Peninsula: U.S. Geological Survey Open-File Report 88-666, 128 p., scale 1:250,000.

  • Deposit

    Ellis, W.T., and Apel, R.A., 1990, Unga/Alaska Peninsula 1990 final report, Battle Mountain Exploration Company report, 49 p., 29 map sheets at various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Ellis, W.T., and Randolph, D., 1991, Unga project 1991 final report: Battle Mountain Exploration Company report, 36 p. 13 map sheets at various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)

  • Deposit

    Wilson, F.H., Detterman, R.L., Miller, J. W., and Case, J.E., 1995, Geologic map of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles, Alaska: U.S. Geological Survey Miscellaneous Investigation Series Map I-2272, 1 map sheet, scale 1:250,000.

Comments on the references

  • Primary Reference = Peterson and others, 1983

General comments

Subject category Comment text
Deposit Model Name = Epithermal gold veins

Reporter information

Type Date Name Affiliation Comment
Reporter 11-JAN-01 S.H. Pilcher U.S. Geological Survey