Unnamed (on east side of West Fork Maclaren River) (ARDF #MH060) Cu

Unnamed (on east side of West Fork Maclaren River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Cu
Other commodities	Ag
Ore minerals	chalcocite; malachite
Gangue minerals	epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale	MH
Quadrangle map, 1:63,360-scale	B-6
Latitude	63.2504
Longitude	-146.7302
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is at an elevation of about 4,000 feet, about 1,300 feet south of the center of section 23, T. 19 S., R. 5 E., Fairbanks Meridian. The site corresponds to locality 16 in figure 4 of Cobb (1979 [OFR 79-238]). The location is probably accurate within one-quarter mile.

Geologic setting

Geologic description Rocks near the site are andesitic to basaltic volcanic rocks of the Nikolai Greenstone of Late Triassic age, a characteristic unit of the Wrangellia terrane (Nokleberg and others, 1981). Chalcocite or its oxidation product malachite occur in quartz-epidote veinlets and vesicles partly filled with quartz-epidote. The copper minerals also occur on fracture or joint surfaces of the host andesite and basalt. Copper is typically accompanied by some silver.
Geologic map unit	(-146.732467715688, 63.2499634292458)
Mineral deposit model	Weak copper mineralization of cupriferous volcanic rocks. Basaltic Cu (Cox and Singer, 1986; model 23).
Mineral deposit model number	23
Age of mineralization	Post-Late Triassic. It also postdates a folding event that occurred in pre-Late Jurassic time (Stout, 1976, p. 30-31). It probably occurred in the Cretaceous during regional metamorphism and granitic plutonism (Nokleberg and others, 1986) or in the early Tertiary at about the time of emplacement of dacite porphyry dikes (Stout, 1976, p. 23, 31).

Production and reserves

Workings or exploration	Natural exposures; copper minerals were found during geochemical investigations (Smith and others, 1973, 1975).
Indication of production	None

References

References Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Mount Hayes quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-238, 140 p. Nokleberg, W.J., Aleinikoff, J.N., and Lange, I.M., 1986, Cretaceous deformation and metamorphism in the northeastern Mount Hayes quadrangle, eastern Alaska Range, in Bartsch-Winkler, Susan, and Reed, K. M., eds., Geologic studies in Alaska by the U.S. Geological Survey during 1985: U.S. Geological Survey Circular 978, p. 64-69 Nokleberg, W.J., Lange, I.M., Roback, R.C., Yeend, Warren, and Silva, S.R., 1991, Map showing locations of metalliferous lode and placer mineral occurrences, mineral deposits, prospects, and mines, Mount Hayes quadrangle, eastern Alaska Range, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1996-C, 42 p., 1 sheet, scale 1:250,000. Smith, T.E., Kline, J.T., and Coursey, N.D., 1975, Analyses of stream-sediment samples, Mt. Hayes B-6 Quadrangle, south-central Alaska: Alaska Division of Geological & Geophysical Surveys Alaska Open-File Report 70, 2 p., 2 sheets, scale 1:63,360. Smith, T.E., Trible, T.C., and Stein, D.R., 1973, Analyses of rock and stream-sediment samples, Mt. Hayes A-6 quadrangle, south-central Alaska: Alaska Division of Geological and Geophysical Surveys Geochemical Report 26, 1 plate, scale 1:63,360. Stout, J.H., 1976, Geology of the Eureka Creek area, east-central Alaska Range: Alaska Division of Geological and Geophysical Surveys Geologic Report 46, 32 p., 1 plate, scale 1:63,360.
Reporters	W.T. Ellis (Alaska Earth Science), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS)
Last report date	7/30/2001