Maclaren Glacier

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu; Fe
Other commodities Ag; Au; Cr; Ni; Zn
Ore minerals azurite; chalcopyrite; gold; magnetite; malachite; sphalerite
Gangue minerals calcite; diopside; garnet

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale B-5
Latitude 63.3014
Longitude -146.4932
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect extends for about 0.3 mile along a gully from an elevation of about 4,000 to 5,500 feet. The center of the prospect is about 2.6 mile north-northeast of the mouth of the East Fork Maclaren River. It is about 0.6 mile west-northwest of the center of section 6, T.19 S., R. 7 E.

Geologic setting

Geologic description

The Maclaren Glacier deposit is along a steeply dipping, west-northwest-striking fault that separates Triassic limestone and gabbro to the south from Triassic argillite to the north (Rose, 1966; Nokleberg and others, 1991; 1992 [MF]; 1992 [Open-File]. Locally, the argillite is intruded by granodiorite of probable Cretaceous age. For about 0.3 mile, limestone is replaced by garnet, diopside, up to 20 percent magnetite, and locally sphalerite and chalcopyrite which is partly oxidized to azurite and malachite. The skarn zone is up to several hundred feet in width. The source of the mineralization may be the Cretaceous granodiorite (Nokleberg and others, 1991).
The mineralized zones are only a few feet or less in length and width. A sample of magnetite skarn contained 16.9 percent iron, 2.8 percent copper, 0.12 percent chromium, 0.14 percent nickel, 45 parts per billion (ppb) gold, and 1 ppb silver (Kurtak and others, 1992). Locally the skarn contains more zinc and precious metals; one sample contained 5.5 percent zinc, 2.5 percent copper, 30 parts per million (ppm) silver, and 3.7 ppm gold (Nokleberg and others, 1991).
Geologic map unit (-146.495466445148, 63.3009715984482)
Mineral deposit model Cu skarn? (Cox and Singer, 1986; model 18b?).
Mineral deposit model number 18b?
Age of mineralization Possibly Cretaceous based on the nearness of a granitic pluton of that age.
Alteration of deposit Base and precious metals in skarn zones in limestone.

Production and reserves

Workings or exploration Only limited sampling by state and federal agencies.
Indication of production None
Reserve estimates None.
Production notes None.

References

References

Bittenbender, P.E., Bean, K.W., Kurtak, J.M., and Deininger, James Jr., 2007, Mineral assessment of the Delta River Mining District area, east-central, Alaska: U.S. Bureau of Land Management, Alaska Technical Report 57, 675 p.
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (USGS); D.J. Grybeck (Contractor, USGS)
Last report date 5/13/2012