Jimmy Lake Occurrence, McGrath Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Jimmy Lake Occurrence	Occurrence
McGrath Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Location: This occurrence is at ane elevation of about 5,000 feet, in the head of a cirque valley, 1.4 miles northeast of Jimmy Lake. The map site is in the southwest 1/4 of section 13, T 19 N, R 22 W, of the Seward Meridian. This is locality 12 of Cobb (1972 [MF 412]; 1976 [OF 76-485]) and locality 11 and 12 of Gamble and others (1989). The location is probably accurate to within 1/4 mile.
Geology: Reed and Elliott (1970) reported that an altered and mineralized biotite granite stock is present at this locality. Mineralization, mostly identified in float boulders and cobbles, includes (1) altered granite that contains less than 5 percent disseminated galena and sphalerite, (2) altered granite that contains veinlets of quartz, sphalerite, galena, and chalcopyrite, and (3) altered granite that contains a 1-inch-wide quartz-molybdenite vein. The alteration consists of variably developed replacement of granite by quartz, sericite, kaolinite, and albite. Samples contain as much as 15,000 ppm copper, 300 ppm silver, and greater than 20,000 ppm lead, 2,000 ppm molybdenum, and 10,000 ppm zinc. Stream sediment samples from the area contain high contents of silver, arsenic, copper, lead, and zinc. The biotite granite stock contains accessory fluorite and intrudes upper Mesozoic clastic sedimentary rocks and possibly overlying Tertiary volcanic rocks (Cobb and Reed, 1981).
Workings: Reconnaissance sampling has been completed in this area (Reed and Elliott, 1970).
Age: Tertiary. Mineralization crosscuts Tertiary granite.
Alteration: Granite locally replaced by quartz-sericite-kaolinite-albite assemblages.

Commodities (Major) - Ag, Cu, Mo, Pb, Zn
Development Status: None
Deposit Model: Polymetallic veins? and porphyry Cu-Mo? (Cox and Singer, 1986, models 22c and 2

Other Databases

Link to USGS - Alaska:	LH012

Other Regions, Features and Areas containing this locality

References