Humboldt Mine, Juneau Mining District, Juneau, Alaska, USAi

Regional Level Types
Humboldt Mine	Mine
Juneau Mining District	Mining District
Juneau	City Borough
Alaska	State
USA	Country

Location: The Humboldt mine is at an elevation of approximately 1000 feet on the north side of Gold Creek. It is 1 mile southeast of Mt. Juneau and immediately north of Ebner Falls. It is in the SW1/4NE1/4 section 13, T. 41 S., R. 67 E. of the Copper River Meridian. The location is accurate.
Geology: The Humboldt mine was discovered in 1882 and was developed by 6 adits and over 400 feet of underground workings. This area was explored extensively by Echo Bay Mines Ltd. from the mid-1980's through the 1990's. Approximately 1,400 tons of ore was mined from the Humboldt Mine between 1882 and 1905. The deposit consists of black phyllite with boudinaged quartz veins, and metagabbro sills and dikes (Redman and others, 1989). The quartz veins contains pyrrhotite, as well as minor sphalerite and galena. U.S. Bureau of Mines samples contained up to 35.9 ppm gold (Redman and others, 1989). This mine is in the Juneau Gold Belt, which consists of more than 200 gold-quartz-vein deposits that have produced nearly 7 million ounces of gold. These gold-bearing mesothermal quartz vein systems form a zone 160 km long by 5 to 8 km wide along the western margin of the Coast Mountains. The vein systems are in or near shear zones adjacent to west-verging, mid-Cretaceous thrust faults. The veins are hosted by diverse, variably metamorphosed, sedimentary, volcanic, and intrusive rocks. From the Coast Mountains batholith westward, the host rocks include mixed metasedimentary and metavolcanic sequences of Carboniferous and older, Permian and Triassic, and Jurassic-Cretaceous age. The sequences are juxtaposed along mid-Cretaceous thrust faults (Miller and others, 1994). The sequences are intruded by mid-Cretaceous to middle Eocene plutons, mainly diorite, tonalite, granodiorite, quartz monzonite, and granite. Sheetlike tonalite plutons emplaced just east of the Juneau Gold Belt and undeformed granite and granodiorite bodies that are emplaced farther to the east are between 55 and 48 Ma (Gehrels and others, 1991). The structural grain of the belt is defined by northwest-striking, moderately to steeply northeast-dipping, penetrative foliation that developed between Cretaceous and Eocene time (Miller and others, 1994). The majority of the veins in the Juneau Gold Belt strike northwest. Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).
Workings: The Humboldt mine was discovered in 1882 and was developed by 6 adits and over 400 feet of underground workings. This area was explored extensively by Echo Bay Mines Ltd. from the mid-1980's through the 1990's.
Age: Isotopic dates indicate that the auriferous veins in the Juneau Gold Belt formed between 56 and 55 Ma (Miller and others, 1994; Goldfarb and others, 1997).
Production: Approximately 1,400 tons of ore was mined from the Humboldt Mine between 1882 and 1905.

Commodities (Major) - Au; (Minor) - Ag, Pb, Zn
Development Status: Yes; small
Deposit Model: Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	JU147

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References