Northern Belle; Elmira; Yellowjacket; Boston; Troy Mine, Juneau Mining District, Juneau, Alaska, USAi

Regional Level Types
Northern Belle; Elmira; Yellowjacket; Boston; Troy Mine	Mine
Juneau Mining District	Mining District
Juneau	City Borough
Alaska	State
USA	Country

Location: The Northern Belle Mine is at an elevation of about 2,500 feet, about 2.5 miles east-northeast of Pt. Sherman on Lynn Canal and 1 mile southwest of Lions Head Mountain in the Kakuhan Range. It is in the SE1/4 section 4, T. 35 S., R. 62 E. of the Copper River Meridian. The location is accurate.
Geology: The deposit at Northern Belle Mine consists of several quartz veins and associated vein stockworks. The deposit includes the Northern Belle, Elmira, and Yellowjacket deposits. The veins strike N 5-30 E and dip 55-70 SE. The Northern Belle stockworks is about 35 feet wide and has been traced along strike for 1,500 feet and vertically for 636 feet. The Elmira vein is less well defined than the Northern Belle, and may be the extension of the Yellowjacket vein. It can be traced intermittently for 1200 feet along a N 28 E strike, and is 1-5 feet thick (Kucinski and others, 1985). The Northern Belle deposit was discovered prior to 1896 and was mined between 1896 and 1897. There were 2 adits and 2 open stopes. The only open adit is 105 feet long. A total of 940 ounces of gold was recovered from 2,302 tons of ore. Reportedly, 78% of the gold in the deposit was free-milling (Redman and others, 1989). Placid Oil Co. explored the Northern Belle stockworks with surface and underground sampling in 1985 and tested the Elmira vein with 6 surface drill holes in 1984 and 1985 (Kucinski, 1985). The site is in the Kensington project area (see JU029), currently (2001) under control of Coeur Alaska. The Northern Belle Mine 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 Northern Belle deposit was discovered prior to 1896 and was mined between 1896 and 1897. There were 2 adits and 2 open stopes. The only open adit is 105 feet long. Placid Oil Co. explored the Northern Belle stockworks with surface and underground sampling in 1985 and tested the Elmira vein with 6 surface drill holes in 1984 and 1985 (Kucinski, 1985). The site is in the Kensington project area (see JU029), currently (2001) under control of Coeur Alaska.
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: A total of 940 ounces of gold was recovered from 2,302 tons of ore. Reportedly, 78% of the gold in the deposit was free-milling (Redman and others, 1989).

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

Other Databases

Link to USGS - Alaska:	JU032

Other Regions, Features and Areas containing this locality

References