Mother Lode Prospect, Juneau Mining District, Juneau, Alaska, USAi

Regional Level Types
Mother Lode Prospect	Prospect
Juneau Mining District	Mining District
Juneau	City Borough
Alaska	State
USA	Country

Location: The Mother Lode prospect is at an elevation of about 1,900 feet, near the ridge crest between Favorite Channel and the head of Boulder Creek. It is near the NE corner of section 22, T. 38 S., R. 64 E. of the Copper River Meridian. The location is accurate.
Geology: The Mother Lode prospect consists of a series of quartz veins and masses in metamorphosed volcanic conglomerate (Knopf, 1912). The veins strike northerly and dip 35 W. They are up to 3 feet thick and contain arsenopyrite and pyrite. The deposit was discovered in the late 1890's. Workings include a 10-foot decline and a trench. U.S. Bureau of Mines samples contained up to 8.8 ppm gold (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).
Workings: The prospect was discovered in the late 1890's. Workings include a 10-foot decline and a trench. U.S. Bureau of Mines samples contained up to 8.8 ppm gold (Redman and others, 1989).
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).

Commodities (Major) - Au
Development Status: None
Deposit Model: Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a)

Other Databases

Link to USGS - Alaska:	JU093

Other Regions, Features and Areas containing this locality

References