Horrible; Savage Mine, Juneau District, Juneau Borough, Alaska, USA
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Location: The Horrible Mine is at an elevation of about 2,150 feet, 2 miles northeast of Pt. Sherman on Lynn Canal and 1 mile west-southwest of Lions Head Mountain in the Kakuhan Range. The Horrible Mine is marked on the Juneau D-4 topographic map. It is approximately 1/2 mile northwest of the Kensington Mine (JU029), in the NW1/4 section 4, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.
Geology: The deposit at the Horrible Mine consists of a quartz vein that was discovered about 1887 and by 1912 was developed by a 84-foot adit, a 408-foot adit, a 230-foot crosscut, and a 20-foot winze (Redman and others, 1989). The mine produced 75 ounces of gold from 500 tons of ore, although 1,500 tons were mined from stopes (Redman and others, 1989). The main (Savage) vein in the Horrible Mine trends northerly and dips 45-75 east. It is in Jualin Diorite and consists of a primary quartz vein and associated stockworks quartz veins (Redman and others, 1989). The deposit has been extensively drilled by Placid Oil Co. and Echo Bay Mines-Coeur Alaska, and is currently (2001) controlled by Coeur Alaska. In 1988, a haulage tunnel for the Kensington Mine (JU029) was completed at the 800 elevation. The Horrible deposit, which was intersected by the main Kensington haulage drift, contains an inferred reserve of 3.93 million tons of ore that contains 0.11 ounce gold per ton (Swainbank and other, 1991). The Horrible Mine is in the Kensington project area, that in 2001 was controlled by Coeur Alaska. It 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).
Workings: The Horrible vein was discovered about 1887 and by 1912 it was developed by a 84-foot adit, a 408-foot adit, a 230-foot crosscut and a 20-foot winze (Redman and others, 1989). The deposit has been extensively drilled by Placid Oil Co. and Echo Bay Mines-Coeur Alaska and is currently (2001) controlled by Coeur Alaska. In 1988, a haulage tunnel for the Kensington Mine (JU029) was completed at the 800 elevation.
Age: 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: 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: The Horrible mine produced 75 ounces of gold from 500 tons of ore, although 1,500 tons were mined from stopes (Redman and others, 1989).
Reserves: The Horrible deposit contains an inferred reserve of 3.93 million tons grading 0.11 ounce gold per ton (Swainbank and other, 1991). The Kensington project area, as defined by Coeur, Alaska, includes the Kensington (JU029), Horrible and other veins, that collectively contain over 1.96 million ounces of gold in the proven and probable categories (Bundtzen and others, 1996).
Commodities (Major) - Au; (Minor) - Ag, Cu, Pb, Zn
Development Status: Yes; small
Deposit Model: Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
20 entries listed. 16 valid minerals.
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Bundtzen, T.K., Swainbank, R.C., Clough, A.H., Henning, M.W., and Charlie, K.M., 1996, Alaska's mineral industry, 1995: Alaska Division of Geological and Geophysical Surveys Special Report 50, 72 p. Coeur d'Alene Mines Corporation, 2001, Corporate website: http://www.ceour.com; accessed August 2002 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. Knopf, Adolph, 1911, Geology of the Berners Bay region, Alaska: U.S. Geological Survey Bulletin 446, 58 p. 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., Gehrels, G,E., and Snee, L.W., 1994, Genetic links among fluid cycling, vein formation, regional deformation, and plutonism in the Juneau gold belt, southeastern Alaska: Geology, v. 22, p. 203-206 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. Redman, E.C., Maas, K.M., Kurtak, J.M., and Miller, L.D., 1989, Bureau of Mines Mineral Investigations in the Juneau Mining District, Alaska, 1984-1988, Volume 2--Detailed mine, prospect, and mineral occurrence descriptions, Section D, Juneau Gold Belt Subarea: U.S. Bureau of Mines Special Publication, 424 p. Swainbank, R.C., Bundtzen, T.K., and Wood, J.E., 1991, Alaska's mineral industry, 1990: Alaska Division of Geological and Geophysical Surveys Special Report 45, 78 p.