Unnamed (west of upper Brown Creek) (ARDF #ID019) Fe

Unnamed (west of upper Brown Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Fe
Other commodities	Ag; Cu; Sb
Ore minerals	pyrrhotite
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	ID
Quadrangle map, 1:63,360-scale	D-2
Latitude	62.93035
Longitude	-156.81769
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is at an elevation of about 2,400 feet on a knob near the head of Brown Creek. It is about 0.4 mile north-northwest of hill 2665 in the SW1/4, section 23, T. 33N., R. 40W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description This occurrence consists of a pod of pyrrhotite in dense hornfels, about 650 feet from the east contact of the Cretaceous, Beaver Mountains pluton. The pod is poorly exposed. From rubble scattered across the hillside, the pod is is estimated to be 6 feet thick and 90 feet long. Two grab samples contained an average of about 20 percent iron, 1.0 parts per million (ppm) silver, 200 ppm copper, and 40 ppm antimony (Miller and Bundtzen, 1994; Miller, Bundtzen, and Gray, 2005).
Geologic map unit	(-156.820049369061, 62.9297041851441)
Mineral deposit model	Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number	22c
Age of mineralization	Probably related to the Beaver Mountains pluton which has been dated at 70.1 Ma. (Bundtzen and Laird, 1982).
Alteration of deposit	In hornfels near contact of granitic pluton.

Production and reserves

Workings or exploration	The occurrence was mapped and sampled by the Alaska Division of Geological and Geophysical Surveys in 1979 (Bundtzen and Laird, 1982).
Indication of production	None

References

References Bundtzen, T.K., and Laird, G.M., 1982, Geologic map of the Iditarod D-2 and eastern D-3 quadrangles, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 72, 1 sheet, scale 1:63,360. McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet.
Reporters	T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date	2/4/2003