Unnamed Occurrence (ARDF - WI077; near junction of Fall and Michigan Creeks), Koyukuk Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - WI077; near junction of Fall and Michigan Creeks)	- not defined -
Koyukuk Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: This occurrence is the locations of several rock samples in an area about 0.2 mile in diameter (Dillon and others, 1981; Plate 1, samples 467 to 472 and 474 and 475 [AOF 133B]). The area is about 6 miles southwest of Ipnek Mountain and about 0.2 mile northwest of the junction of Fall and Michigan Creeks. The occurrence is at an elevation of about 1,550 feet, 0.4 mile south-southwest of the center of section 25, T. 29 N., R. 17 W., of the Fairbanks Meridian. The location is accurate.
Geology: Dillon and others (1981 [AOF 133B]) collected mineralized rock samples at several sites in an area of about a half mile in diameter. The mineralization occurs in layers and veins of massive pyrrhotite, chalcopyrite, sphalerite, arsenopyrite, cassiterite, rutile, pyrite and possible molybdenite. The pyrrhotite is partly altered to marcasite. Eight samples collected by Dillon and others contain up to 82,000 ppm arsenic, 700 ppm cobalt, 1,360 ppm copper, 8.28 ppm gold, 135 ppm lead, 50 ppm tin, and 329 ppm zinc. The sulfide layers and veins are up to 30 cm. thick in actinolite-biotite felsite interlayered with marble and garnet-quartz-albite-muscovite schist. Hornfelsed calc-silicate rocks along the contact with the felsite contain disseminated pyrite(?). Dillon and others (1986) map the area as Devonian and Devonian(?) interlayered felsic and mafic intrusive and extrusive rocks, locally mixed with clastic sedimentary rocks. They indicate that the upper Devonian felsic schist is regionally associated with copper deposits.
Workings: Only surface sampling.
Alteration: Alteration of pyrrhotite to marcasite; oxidation of sulfides.

Commodities (Major) - As, Au, Cu; (Minor) - Ag, Co, Pb, Ti, Zn
Development Status: None
Deposit Model: Polymetallic vein(?) (Cox and Singer, 1986; model 22c)

Other Databases

Link to USGS - Alaska:	WI077

Other Regions, Features and Areas containing this locality

References