Big Four Creek

Mine, Active?

Alternative names

Big Four Gulch

Commodities and mineralogy

Main commodities Au
Other commodities Ag; Cu; Cr; Hg; Pt
Ore minerals chromite; gold; iron-platinum alloy; mercury; native copper

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-2
Latitude 63.1854
Longitude -144.8212
Nearby scientific data Find additional scientific data near this location
Location and accuracy 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).

Geologic setting

Geologic description

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.
Geologic map unit (-144.823429892638, 63.1850050337006)
Mineral deposit model Placer Au-PGE (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Tertiary to Holocene.
Alteration of deposit The 'round wash' conglomerate is extensively altered to clay (Chapin, 1919).

Production and reserves

Workings or exploration 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 1950s (Foley, 1992).
Indication of production Yes; small

References

MRDS Number A011773

References

Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date 7/3/2003