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Pass Lake West

Occurrence, Inactive

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Commodities and mineralogy

Main commodities Ag; Cu
Other commodities Mo; Zn

Geographic location

Quadrangle map, 1:250,000-scale LC
Quadrangle map, 1:63,360-scale B-5
Latitude 60.41
Longitude -154.55
Nearby scientific data Find additional scientific data near this location
Location and accuracy An extensive arcuate shaped occurrence centered approximately at a point 8 km upstream from the mouth of an unnamed northwest flowing tributary of the Koksetna River. The occurrence extends roughly 6.5 km northwest and 8 km south of this location and is about 2.9 km wide. Locality 15 of Nelson and others (1985) and locality 23 of MacKevitt and Holloway (1977). Sec. 30, T. 4 N., R. 30 W., of the Seward Meridian. Locality accurate within 1.6 km.

Geologic setting

Geologic description

Weak geochemical anomalies associated with granite and rhyolite that may include breccia pipes. Granite is less fractured and iron-stained than rhyolite (Nelson and others, 1985).
The granite is part of the numerous, mostly quartz monzonite intrusive bodies found in the central part of the Lake Clark 1:250,000 scale quadrangle mapped and identified by Eakins and others (1978); (Nelson and others, 1983; unit TKi5). One of these plutons yielded a potassium-argon biotite age of 71.3 +/- 2.1 m.y. (Eakins and others, 1978). The rhyolite is part of unit Tv. Unit Tv is described by Nelson and others (1983) to include: rhyolitic breccia, ash-flow tuff, flows, and intrusive rocks and subordinate mafic to intermediate flows. Potassium-argon ages for this unit (Tv) range from 56.2 to 62.7 m.y. indicating a Tertiary age for these rocks (Eakins and others, 1978).
Geologic map unit (-154.552230967756, 60.4093279707273)
Mineral deposit model Porphyry Cu-Mo? (Cox and Singer, 1986; model 21a?).
Mineral deposit model number 21a?
Age of mineralization Late Cretaceous or younger. Rocks of the quartz monzonite unit yielded a potassium-argon biotite age of 71.3 +/- 2.1 m.y. (Eakins and others, 1978). Potassium-argon ages for the rhyolite, unit Tv, range from 56.2 to 62.7 m.y. (Eakins and others, 1978)
Alteration of deposit Unknown

Production and reserves

Workings or exploration Unknown, although Resource Associates of Alaska (1976) completed a sampling program that identified the occurrence.
Indication of production None
Reserve estimates No reserves
Production notes No production

Additional comments

Site is in Lake Clark National Park and Preserve.

References

MRDS Number A106361

References

Eakins, G.R., Gilbert W.G., and Buntzen, T.K., 1978, Preliminary bedrock geology and mineral resource potential of west-central Lake Clark quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Open-File Report 118, 15 p., 2 plates, scale 1:25,000.
MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous mineral deposits in the western part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-F, 38 p., 1 sheet, scale 1:1,000,000.
Nelson, W.H., Carlson, C., and Case, J.E., 1983, Geologic map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-A, 1 sheet, scale 1:250,000.
Nelson, W.H., King, H.D., Case, J.E., Tripp, R.B., Crim, W.D., and Cooley, E.F., 1985, Mineral resource map of the Lake Clark quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-1114-B, 1 sheet, scale 1:250,000.
Resource Associates of Alaska, Inc., 1976, Geology and geochemistry of certain land within the Lake Clark National Park: Contract report for U.S. Bureau of Mines, Contract JO166108, 7 v.
Reporters D.P. Bickerstaff (USGS)
Last report date 6/15/1998