Gold King

Prospect, Active

Commodities and mineralogy

Main commodities Ag; Au
Other commodities Cu
Ore minerals chalcopyrite; gold; pyrite
Gangue minerals ankerite; ferroan dolomite; quartz

Geographic location

Quadrangle map, 1:250,000-scale JU
Quadrangle map, 1:63,360-scale D-4
Latitude 58.8623
Longitude -135.0449
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Gold King prospect is on the northeast side of the head of Johnson Creek at an elevation of about 2,100 feet, about 1 mile south-southeast of Lions Head Mountain. It is in the SE1/4 section 3, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description

The Gold King prospect was discovered prior to 1903 and developed by a 64-foot adit with 20 feet of drifts, and 2 other adits, 30 feet and 122 feet long. The deposit is in Jualin Diorite and consists of a series of quartz veins ranging from a few inches to 2 feet thick. The veins strike SE and dip 75 NE. They contain 1% to 20% pyrite and minor chalcopyrite. U.S. Bureau of Mines samples contained up to 36.8 ppm gold and 18.0 ppm silver. A sample of altered diorite contained 2.5 ppm gold (Redman and others, 1989). Bear Creek Mining Co. and International Curator Resources Ltd. undertook a cursory investigation of the Gold King adit in 1984-1988 and collected 24 samples. One sample was from an exposure of pyrite-rich diorite 50 feet from the Gold King vein; it assayed 0.785 ounce of gold per ton (Barnett, 1989). The prospect is currently (2001) controlled by Coeur Alaska.
The Gold King prospect is in 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 are in Early Cretaceous (105 Ma) Jualin Diorite, which intrudes Upper Triassic metabasalt. The Jualin Diorite is generally massive, jointed, blocky, quartz monzonite to quartz monzodiorite. Gold occurs in low-sulfide, quartz-carbonate veins that contain pyrite and tellurides; the veins are marked by distinctive ankeritic alteration zones. There are both extensional and shear veins that generally strike north to northwest and dip east. Discrete vein systems are defined by one or more through-going quartz veins, many of which are in shear zones. Levielle (1991) and Knopf (1911) describe other gangue minerals near vein margins including albite, chlorite, muscovite, and lesser tourmaline, rutile, and apatite. Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization, sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991). Pyrite is the most abundant sulfide mineral, with lesser amounts of chalcopyrite, galena, sphalerite, arsenopyrite, and tetrahedrite. Gold occurs in the native state, in pyrite, and in various telluride minerals such as calaverite, hessite, and petzite (Leveille, 1991; Redman and others, 1989). The vein paragenesis consists of early quartz, carbonates, albite and pyrite, followed by deposition of base and precious metals. Gold, galena and the tellurides were the last to be deposited (Leveille, 1991). The age of hydrothermal muscovite from veins at Kensington Mine (JU029) varies from 53.4 Ma to 56.5 Ma (Miller and others, 1994). This coincides with the 55 Ma age of the other mesothermal gold vein deposits in the Juneau Gold Belt (Goldfarb and others, 1997).
Geologic map unit (-135.04671371312, 58.8619720047918)
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).
Alteration of deposit Hydrothermal alteration adjacent to the veins is characterized by reddish-brown ferroan dolomite alteration (Miller and others, 1995). Other alteration includes sericitization of plagioclase, chloritization and sulfidization of mafic minerals, and albitization of feldspars (Leveille, 1991).

Production and reserves

Workings or exploration The Gold King deposit was discovered prior to 1903 and developed by a 64-foot adit with 20 feet of drifts, and 2 other adits, 30 feet and 122 feet long. Bear Creek Mining Co. and International Curator Resources Ltd. explored the area in 1984-1988. The prospect is currently (2001) controlled by Coeur Alaska.
Indication of production None

References

References

Barnett, J.C., 1989, Jualin gold project, 1988 progress report, Berners Bay District: Unpublished report for International Curator Resources, Ltd., 75 p.
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.
Leveille, R.A., 1991, Geology and gold deposits of the Jualin mine area, Berners Bay district, southeastern Alaska: Fairbanks, University of Alaska, M.S. thesis, 200 p.
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