Ivanhoe

Mine, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Cu
Ore minerals chalcopyrite; native copper; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.8823
Longitude -135.1029
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Ivanhoe Mine is at an elevation of about 2,300 feet, in the Kakuhan Range, 2 miles northeast of Pt. Sherman on Lynn Canal and 1 mile west of Lions Head Mountain. The mine is marked on the Juneau D-4 topographic map. It is in the NE1/4 section 32, T. 34 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Ivanhoe Mine was discovered in 1896. In 1897, a 20-stamp mill was installed and a 5,700-foot tramway was constructed. By 1902, the mine had produced 340 ounces of gold from 3,500 tons of ore. The mine has 1,100 feet of workings and 2 stoped areas, 6 adits, 1 crosscut, and a 100-foot shaft.
The Ivanhoe mine developed a quartz vein entirely contained in metamorphosed basalt, unlike most other veins in the Berners Bay district, which are typically are hosted in Jualin Diorite. The vein trends northerly to northwesterly and dips 35 to 55 East. It varies from 1 foot to 9 feet thick and has been traced on the surface for 1,500 feet along strike. The contact between the vein and the metabasalt is sheared and fragments of basalt are common in the vein. Pyrite and chalcopyrite occur in the vein as small clots or thin bands. Native copper occurs in the deeper stopes as dendrites on fractures in the quartz. This is the only occurrence of native copper in the Juneau Gold Belt (Redman and others, 1989). U.S. Bureau of Mines samples contained up to 0.14% copper and 15 ppm gold. Their weighted average over 4.3 feet was 2.3 ppm gold and 5.9 ppm silver. (Redman and others, 1989).
The Ivanhoe Mine is within the Berners Bay district at the north end of the Juneau Gold Belt. The district is characterized by a series of structurally-controlled mesothermal, gold-bearing quartz veins. Most of the veins cut the Lower Cretaceous Jualin Diorite, which intrudes Mesozoic (Upper Triassic) metabasalt (Miller and others, 1995). The age of mineralization in the Berners Bay area is about 55 Ma, the same as the other mesothermal gold vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Geologic map unit (-135.104721295183, 58.8819693605484)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number 36a
Age of mineralization The age of mineralization in the Berners Bay district is about 55 Ma, the same as the other mesothermal gold-quartz-vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).

Production and reserves

Workings or exploration The Ivanhoe Mine was discovered in 1896. In 1897, a 20-stamp mill was installed and a 5,700-foot tramway was constructed. The mine has 1,100 feet of workings and 2 stoped areas, 6 adits, 1 crosscut and a 100-foot shaft.
Indication of production Yes; small
Reserve estimates The Ivanhoe Mine has a resource of 180,000 tons of ore that contains 0.7 ounce of gold per ton and 0.2 ounce of silver per ton (Redman and others, 1989).
Production notes By 1902, the mine had produced 340 ounces of gold from 3,500 tons of ore.

References

MRDS Number A012074

References

Goldfarb, R.J., Miller, L.D., Leach, D.L., and Snee, L.W, 1997, Gold deposits in metamorphic rocks in Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 151-190.
Miller, L.D., Goldfarb, R.J., Snee, L.W., Gent, C.A., and Kirkham, R.A., 1995, Structural geology, age, and mechanisms of gold vein formation at the Kensington and Jualin deposits, Berners Bay district, southeast Alaska: Economic Geology, v. 90, p. 343-368.
Reporters J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date 12/15/2001