Post Lake Prospect, McGrath Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Post Lake Prospect	Prospect
McGrath Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Geological features are similar to Chip-Loy prospect (MG032) in McGrath A-3 quadrangle.
Location: The Post Lake prospect is located about 1 mile (1.5 km) east of Post River and 1.8 miles (2.9 km) south of Post Lake on a low, glaciated bench level in sec. 32, T. 24 N., R. 23 W., of the Seward Meridian. Location is precisely known; the reporter investigated the mineralization in 1983.
Geology: The Post Lake prospect consists of massive, sulfide veins and replacement zones that cut Ordovician to Lower Silurian shale of the Post River Formation, a unit of the Dillinger subterrane (Bundtzen and others, 1988; Bundtzen, Harris, and Gilbert, 1997). The mineralized area is about 122 meters south of the contact between the Post River Formation and a small quartz monzonite stock. A prospect map has been published by Bundtzen and others (1988). Most of the sulfide mineralization consists of massive pyrrhotite, and minor to sparse chalcopyrite and arsenopyrite. Sulfide masses vary from 0.5 to 2 meters in thickness and strike lengths of 20 to 80 meters. Most of the mineralization trends about N25W, parallel to the nearby Bowser Creek fault. Bundtzen and others (1988) reported values as high as 570 ppm copper, 302 ppm zinc, 378 ppm arsenic, 139 ppm cobalt, and 637 ppm nickel. Five chip samples taken across the massive sulfides averaged about 33.5 percent iron. Elevated cobalt and nickel values occur in the massive pyrrhotite zones.
Workings: Only surface sampling has been conducted. Bundtzen and others (1988) reported values as high as 570 ppm copper, 302 ppm zinc, 378 ppm arsenic, 139 ppm cobalt, and 637 ppm nickel. Five chip samples taken across the massive sulfide zones averaged about 33.5 percent iron. Elevated cobalt and nickel values occur in the massive pyrrhotite zones.
Age: Inferred to be Tertiary based on ages of plutonic suite in area (Solie and others, 1991).
Alteration: Ferricrete oxidation of massive pyrrhotite zones is extensive and ubiquitous.
Reserves: None.

Commodities (Major) - As, Co, Cu, Ni; (Minor) - Fe, Pb
Development Status: No
Deposit Model: Polymetallic veins (Cox and Singer, 1986; model 22c).

Other Databases

Link to USGS - Alaska:	MG069

Other Regions, Features and Areas containing this locality

References