Big Four Creek; Big Four Gulch Mine, Chistochina Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Big Four Creek; Big Four Gulch Mine	Mine
Chistochina Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Location: Big Four Creek or Gulch, an informal name (not on the 1975 revision of the A-2 quadrangle), is on the south side of the Chistochina River about 1.6 miles northeast of the mouth of Slate Creek, which flows northwesterly into the Chistochina. The Big Four Creek placer mine is mainly in the E1/2NW1/4 section 14, T. 20 S., R. 15 E., Fairbanks Meridian. The location is plotted near the main site of mining, which is south of the 1966 terminus of Chistochina Glacier (Rose, 1967). Most mining has taken place between elevations of 4,300 and 4,600 feet. The location is accurate; it is approximately the same as locality 14 on figure 6 of Cobb (1979 [OFR 79-238]), locality 66 of MacKevett and Holloway (1977), and locality 8 in table 3 of Nokleberg and others (1991).
Geology: Big Four Creek is a short, steep creek cut into Upper Triassic cumulate gabbro, argillite of the Mankomen or Eagle Creek Formations, and, at its head, the Tertiary 'round wash' conglomerate (Rose, 1967). Rose also mapped irregular breccia bodies of uncertain origin in upper Big Four Creek. The pay gravel in the creek is mainly derived from the 'round wash' conglomerate. The 'round wash' consists of gravel and partly indurated cobble and boulder 'stone' locally containing well-rounded to subangular boulders as much as a foot across. Clasts are mainly schist, greenstone, granite, and argillite (Yeend, 1981 [C 823-B]). Gold is shotty to well-worn and is somewhat finer grained than the gold from the Miller Gulch placer (MH296; Moffit, 1912), a deposit also derived from the reworking of 'round wash' conglomerate. Gold is accompanied by some native copper and native mercury. Placer concentrates are mainly (65 to 70 percent) magnetite and 30 percent ilmenite and contain lesser amounts of chromite, pyrite, epidote, garnet, and zircon (Yeend, 1981 [C 823-B]). Small amounts of platinum-group metals (PGE) occur; iron-platinum alloy from the concentrates contained 83 percent platinum and 17 percent iron as determined by electron-microprobe analysis (Foley, 1992). The placer deposit was discovered in 1902, and mining commenced immediately (Mendenhall, 1903; Mendenhall and Schrader, 1903). Mining has continued intermittently to the present.iron-platinum alloy,
Workings: Gold was discovered in Big Four Creek by 1902, and mining commenced immediately (Mendenhall, 1903; Mendenhall and Schrader, 1903). The placer deposit was worked on a small scale intermittently between 1903 and the present (Moffit, 1912, 1944; Yeend, 1981 [C 823-B]; Foley, 1992). The deposit itself is fairly small, and water has often been in short supply, minimizing production (Moffit, 1954). The creek has been mined by mechanized open-cut methods intermittently since the early 1950's (Foley, 1992).
Age: Tertiary to Holocene.
Alteration: The 'round wash' conglomerate is extensively altered to clay (Chapin, 1919).

Commodities (Major) - Au; (Minor) - Ag, Cu, Cr, Hg, Pt
Development Status: Yes; small
Deposit Model: Placer Au-PGE (Cox and Singer, 1986; model 39a).

Other Databases

Link to USGS - Alaska:	MH293

Other Regions, Features and Areas containing this locality

References