Location: The portal of the main adit of the Keystone prospect is on the north bank of Smugglers Creek, about 1.1 mile above its mouth. It is about 0.4 mile west of the center of section 24, T. 72 S., R. 87 E. The location is accurate.

Geology: The Keystone prospect consists of two sets of veins: one is parallel to the foliation of the country rocks and has sharp walls; the other set consists of gash veins that extend into the wallrock. The veins are auriferous and contain pyrite, which also is disseminated in the wall rock. The best ore is at the intersection of the two sets of veins. The rocks in the area consist of metamorphosed andesite, basalt, agglomerate, and tuff, and minor flysch, shale, and phyllite. Eberlein and others (1983) and Brew (1996) consider them to be Paleozoic or Mesozoic in age; Gehrels and Berg (1992) tentatively mapped them as Jurassic or Cretaceous. According to Brooks (1902) and Wright and Wright (1908), the workings on the Keystone prospect consist of a shaft 120 feet deep with drifts and crosscuts from it, and a tunnel with about 700 feet of crosscuts and drifts. Apparently, no workings have been driven since before 1908 and there is no record of production. The tunnel intersects a sheared and brecciated zone 20 to 40 feet wide in greenstone and greenschist. The zone has many irregular quartz veins and lenses an inch to several feet wide; pyrite impregnates much of the rock in the zone. Samples of ore contained $3.20 to $20.00 per ton in gold (at $20.67 per ounce), and averaged about $8 per ton. 28 samples along the workings collected by Munoz (1977) averaged 0.099 ounce of gold per ton. Samples across 5-foot widths varied from 0.01 to 0.44 ounce of gold per ton. Soil geochemistry and and self-potential geophysics have indicated that they are effective in defining the mineralized zone (Maas and others, 1995).

Workings: The workings, all of which date from before WWI, consist of a 120-foot shaft with drifts and crosscuts from it, and a tunnel with drifts and crosscuts that total about 700 feet.

Age: The quartz veins cut country rocks that may be as young as Cretaceous or as old as Paleozoic.

Alteration: Not specifically mentioned; the brecciated and sheared zone that hosts the auriferous quartz veins is impregnated with pyrite.

Commodities (Major) - Au

Development Status: None

Deposit Model: Low-sulfide gold-quartz vein (Cox and Singer, 1986; model 36a).

Other Databases

Link to USGS - Alaska:	CR075

Other Regions, Features and Areas containing this locality

References