Unnamed (northwest of upper Otter Creek) (ARDF #ID123) Ag, Pb

Unnamed (northwest of upper Otter Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities	Ag; Pb
Other commodities	As; Bi; Cd; Cu; Sb; Sn; Zn
Ore minerals	iron oxide
Gangue minerals	quartz

Geographic location

Quadrangle map, 1:250,000-scale	ID
Quadrangle map, 1:63,360-scale	B-4
Latitude	62.4974
Longitude	-157.86111
Nearby scientific data	Find additional scientific data near this location
Location and accuracy	This occurrence is in a saddle of a northeast-trending ridge about 4 miles northeast of Discovery camp on Otter Creek and 0.2 mile northeast of hill 1807. The occurrence is at an elevation of about 1,700 feet near the southwest corner of section 20, T. 28 N., R. 46 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description This occurrence is a zone of quartz stringers in heavily iron-oxide-stained sandstone of the Upper Cretaceous, Kuskokwim Group. The quartz stringers are next to a quartz-feldspar porphyry dike (Bundtzen and others, 1992). The dike trends northeast along the ridge. Grab samples contained up to 200 parts per million (ppm) silver, 2.00 percent lead, more than 2,000 ppm antimony, 2,000 ppm zinc, 200 ppm copper, 50 ppm tin, 1,600 ppm arsenic, 100 ppm cadmium, and 18 ppm bismuth (McGimsey and others, 1988; Bundtzen and others, 1992). The primary sulfides are entirely oxidized, but the original primary minerals probably included galena or a lead sulfosalt and sphalerite.
Geologic map unit	(-157.863508594501, 62.496716656165)
Mineral deposit model	Sn-polymetallic deposit or Polymetallic vein (Cox and Singer, 1986; model 20b or 22c).
Mineral deposit model number	20b or 22c
Age of mineralization	Undated; a nearby intrusion is 70.5 Ma (Bundtzen and others, 1992).
Alteration of deposit	Intense iron-oxide staining.

Production and reserves

Workings or exploration	Surface samples were collected by the U.S. Geological Survey and Alaska Division of Geological and Geophysical Surveys in 1986 (McGimsey and others, 1988; Bundtzen and others, 1992).
Indication of production	None

References

References Bundtzen, T.K., Miller, M.L., Laird, G.M., and Bull, K.F., 1992, Geology and mineral resources of Iditarod mining district, Iditarod B-4 and eastern B-5 quadrangles, southwestern Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 97, 46 p., 2 sheets, 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	5/19/2003