Lemon Creek (ARDF #JU123) Ag, Au, Pb, Zn

Lemon Creek

Prospect, Inactive

Alternative names

Keystone

Commodities and mineralogy

Main commodities	Ag; Au; Pb; Zn
Other commodities	Cu
Ore minerals	chalcopyrite; galena; pyrite; pyrrhotite
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	JU
Quadrangle map, 1:63,360-scale	B-2
Latitude	58.3975
Longitude	-134.4074
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	The Lemon Creek prospect is at an elevation of approximately 1,000 feet, near the headwaters of Lemon Creek. It is 1 mile upstream from the junction of Lemon Creek and Canyon Creek. It is in the SW1/4 SE1/4 section 18, T. 40 S., R. 67 E. of the Copper River Meridian. The location is accurate.

Geologic setting

Geologic description The Lemon Creek lode was discovered in 1890 and consists of three quartz veins in biotite gneiss (Redman and others, 1989). The veins are 6 inches to 1 foot thick and can be traced for up to 300 feet. The veins contain pyrrhotite, galena, sphalerite, and chalcopyrite; the sulfides are concentrated along the hanging wall. The U.S. Bureau of Mines collected six samples that averaged 2.6 ppm gold, 87.0 ppm silver, 2.9 percent zinc, and 0.26 percent lead (Redman and others, 1989). This prospect 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).
Geologic map unit	(-134.409172416179, 58.3971764449211)
Mineral deposit model	Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)
Mineral deposit model number	36a
Age of mineralization	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 and reserves

Workings or exploration	Surface sampling only.
Indication of production	None

References

MRDS Number	A012008
References Gehrels, G.E., McClelland, W.C., Samson, S.D., and Patchett, P.J., 1991, U-Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska: Canadian Journal of Earth Sciences, v. 28, no. 8, p.1285-1300. 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., 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 Redman, E.C., Maas, K.M., Kurtak, J.M., and Miller, L.D., 1991, Section D: Juneau Gold Belt subarea, in U.S. Bureau of Mines, Mineral investigations in the Juneau Mining District, Alaska, 1984-1988: Volume 2 - Detailed mine, prospect, and mineral occurrence descriptions: U.S. Bureau of Mines Special Publication VOL. 2D, 424 p., 19 sheets.
Reporters	J.C. Barnett and L.D. Miller (Juneau, Alaska )
Last report date	12/15/2001