Hetta Mountain

Prospects, Probably inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu; Fe; Zn
Other commodities Co; Mo; Pb
Ore minerals chalcopyrite; pyrrhotite; pyrite
Gangue minerals epidote; garnet; quartz

Geographic location

Quadrangle map, 1:250,000-scale CR
Quadrangle map, 1:63,360-scale A-2
Latitude 55.1974
Longitude -132.5684
Nearby scientific data Find additional scientific data near this location
Location and accuracy These prospects are at an elevation of about 2,800 feet near the summit of Hetta Mountain; they are in the NW1/4 section 14, T. 77 S., R. 85 E.

Geologic setting

Geologic description

The Hetta Mountain prospects are on 14 patented claims. The workings, all of which date from before WW I, consist of three short adits and several trenches (Wright and Wright ,1908; Wright, 1915; Herreid and others, 1978; Maas and others, 1991, 1995). The rocks in the vicinity consist of a fault-bounded block of Late Proterozoic or Cambrian marble of the Wales Group that is surrounded by Cretaceous, albite-epidote hornfels and garnet-bearing hornblende hornfels. The metamorphic rocks are cut by several granitic dikes, and the marble is locally altered to skarn.
In one adit, a shear zone about 80 feet thick in marble contains diopside-garnet skarn with veinlets and blebs of chalcopyrite. In another adit, three short, en echelon pods of massive pyrite, pyrrhotite, and chalcopyrite replace marble along a porphyritic diorite dike (Herreid and others, 1978). A grab sample of rich ore contained 2.2 percent copper, 0.74 percent zinc, 12.3 ounces of silver per ton, 0.10 ounce of gold per ton, 600 parts per million (ppm) molybdenum, 750 ppm cobalt, and 22 ppm lead. Maas and others (1991) collected 15 samples from the prospects. Several had insignificant metal values, but the best contained 4.17 percent copper, 43.8 ppm silver, and 0.572 ppm gold. Wright and Wright (1908) show several additional prospects along the trail from the head of Copper Harbor to Hetta Mountain. At one, at an elevation of about 1,380 feet, a small mass of chalcopyrite is exposed in a 30-foot tunnel.
Geologic map unit (-132.570062195826, 55.1970467969277)
Mineral deposit model Copper skarn (Singer and Cox, 1987; model 18b).
Mineral deposit model number 18b
Age of mineralization Probably Cretaceous.
Alteration of deposit Locally, skarn is developed in marble.

Production and reserves

Workings or exploration The Hetta Mountain prospects are on 14 patented claims. The workings, all of which date from before WW I, consist of three short adits and several trenches.
Indication of production None

Additional comments

The 14 patented claims at this prospect are surrounded by land whose surface and subsurface rights have been conveyed to, or are under application for transfer to, the Sealaska Corporation.

References

MRDS Number A010027

References

Glavinovich, P.S., 1987, Sealaska Corporation Minerals Breifing Book, December 1987: Sealaska Corporation, 40 p. and plates. (Unpublished report held by Sealaska Corporation, Juneau, Alaska).
Hedderly-Smith, D.A., 1997, Results of 1996 reconnaissance sampling at Hetta Lake-Sealaska minerals reconnaissance project: Sealaska Corporation, 17 p.with addendum. (Unpublished report held by the Sealaska Corporation, Juneau, Alaska.)
Hedderly-Smith, D.A., 1999, Inventory of metallic mineral prospects, showings and anomalies on Sealaska lands, 1988 through 1998: Sealaska Corporation, Juneau, Alaska, 217 p. (internal report held by Sealaska Corporation, Juneau, Alaska).
Reporters D.J. Grybeck (Applied Geology)
Last report date 5/1/2004