Centennial

Prospect, Active

Alternative names

Herman Lode
Trench
Popof Island Gold

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Cu; Hg; Pb; Zn
Ore minerals chalcopyrite; galena; gold; pyrite; sphalerite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale PM
Quadrangle map, 1:63,360-scale B-2
Latitude 55.308
Longitude -160.4975
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Centennial prospect is at an elevation of about 300 feet, approximately 2 miles south of the town of Sand Point. It is in the upper half of section 29, T. 56 S., R. 73 W. The location is accurate.

Geologic setting

Geologic description

The host rock at the Centennial prospect is Eocene to Oligocene Popof volcanic rocks (Wilson and others, 1995). At this locality they consist mostly of basalt flows and tuffs.
The names Herman Lode and Trench refer to prospects explored by several adits, pits, and a trench in the early 1900s. A mineralized zone 5 to 10 feet wide was reported to contain free gold (Atwood, 1909). The name Centennial was given to a gold deposit discovered in the same area in 1987 by Battle Mountain Exploration Company. Battle Mountain evaluated the property by detailed mapping and sampling, 484 auger holes, 59 diamond drill holes, 7,275 feet of trenching, and magnetic and VLF-EM geophysical surveys. Battle Mountain estimated that within 175 of the surface, the deposit has a resource of 4.8 million tons with an average grade of 0.042 ounce of gold per ton (Ellis and Harris, 1989).
The Centennial deposit is a large, low grade, disseminated gold lode. The country rocks consist of basalt flows, plugs, dikes, tuffs, and epiclastic deposits that overlie a sedimentary complex. The main mineralized zone occurs in a window eroded through a basalt flow. The mineralization is thought to be controlled in part by a plug margin, and in part by north-northeast-trending high-angle faults and fracture zones from which mineralizing fluids spread out into surrounding permeable rock (Ellis and Harris, 1989). The gold is disseminated in the matrix of the basaltic tuffs and also occurs in fractures and veins that cut the flows. The mineralization seems to have a lower limit at 240 to 400 feet above the sedimentary rocks that are beneath the volcanic rocks. The gold is free and occurs in the plus-25-micron range (Ellis and Harris, 1989). Silver, mercury, and arsenic are associated with the gold in analyses of the samples. Quartz and quartz-calcite veins and veinlets containing galena, sphalerite, pyrite, and some chalcopyrite were cut in some of the drill holes. Their relationship to the gold mineralization is not known. The rocks exhibit pervasive propylitic alteration. The mineralization is accompanied by enrichment in silica and potassium, resulting in deposition of adularia, sericite, and quartz. Argillic alteration is locally present. Calcite stockwork veining is widespread.
Geologic map unit (-160.499511653879, 55.307176941576)
Mineral deposit model Volcanic-hosted disseminated gold deposit.
Age of mineralization Eocene or younger based on the age of the host rock.
Alteration of deposit The host rocks in the area exhibit pervasive propylitic alteration. The mineralization is accompanied by enrichment in silica and potassium, resulting in deposition of adularia, sericite, and quartz. Argillic alteration is locally present. Calcite stockwork veining is widespread.

Production and reserves

Workings or exploration In the early 1900s the prospect area was explored by tunnels, trenches, and pits. In the late 1980s, Battle Mountain Exploration Company evaluated the property by detailed mapping and sampling, 484 auger holes, 59 diamond drill holes, 7,275 feet of trenching, and magnetic and VLF-EM geophysical surveys.
Indication of production None
Reserve estimates Battle Mountain Exploration Company estimated that within 175 of the surface, the deposit has a resource of 4.8 million tons with an average grade of 0.042 ounce of gold per ton (Ellis and Harris, 1989).

Additional comments

This prospect is on land owned by the Aleut Native Corporation.

References

MRDS Number A013198

References

Ellis, W.T., and Harris, D.E., 1989, Centennial prospect 1989 final report: Battle Mountain Exploration Company report, 48 p., 41 map sheets of various scales. (Report held by the Aleut Corporation, Anchorage, Alaska.)
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.)
Redstar Gold Corp., 2012, Growth through discovery: http://www.redstargold.com/in/pdf/RGC-Presentation.pdf (corporate presentation as as of March 20, 2012).
Redstar Gold Corp., 2012, Redstar identified new high-grade gold vein system with 94.7 g/t and 1840 g/t Ag at surface, Unga project, Alaska: http://www.redstargold.com/s/NewsReleases.asp?ReportID=502474 (News release, January 18, 2012).
Webber, B.S., Moss, J.M., Rutledge, F.A., and Sanford, R.S., 1946, Reconnaissance examinations of parts of the Alaska Peninsula and Aleutian Islands southwestern Alaska: U.S. Bureau of Mines, unpublished report of investigations, 40 p. (Report held by the U.S. Geological Survey, Anchorage.)
Reporters S.H. Pilcher (Anchorage, Alaska); D.J. Grybeck (Contractor, USGS)
Last report date 4/1/2012