Unnamed (east of Swan Lake)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Mo
Ore minerals molybdenite

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale C-4
Latitude 55.609
Longitude -131.227
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is about 2.0 miles east of Swan Lake, on the crest of a north-northeast-trending ridge at an elevation of 3650 feet. The site is on the boundary between sections 19 and 20, T. 72 S., R. 92 E., of the Copper River Meridian. It corresponds to loc. 50.1 in Elliott and others (1978). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks near this prospect are pelitic schist and gneiss, and subordinate andesitic and basaltic metavolcanic rocks, that are intruded by Cretaceous stocks, sills, and dikes of feldspar-porphyritic granodiorite, and by small metadiorite plutons of undetermined age (Berg and others, 1988). The strata were regionally metamorphosed to upper greenschist or amphibolite grade in Cretaceous time, and, near some of the granodiorite contacts, subsequently contact metamorphosed to hornblende hornfels. The premetamorphic age range of the strata is unknown. Berg and others (1988, p. 17) assigned them an undivided Mesozoic or Paleozoic age. More recent studies suggest that at least some of the strata may be as old as Precambrian (Crawford and others, 2000).
This occurrence consists of sparsely disseminated, minute particles of molybdenite in a rusty-weathering, 45-foot-thick granodiorite(?) sill that intrudes pelitic paragneiss (Elliott and others, 1978). An analysis of the molybdenite-bearing rock showed 150 ppm Mo (Koch and Elliott, 1978 [OFR 78-156A]). The molybdenite may be a late-stage hydrothermal mineral in the granodiorite.
Geologic map unit (-131.228697284107, 55.6086510873696)
Mineral deposit model Porphyry Mo, low-F? (Cox and Singer, 1986; model 21b)
Mineral deposit model number 21b?
Age of mineralization Cretaceous?
Alteration of deposit Locally conspicuous iron-staining.

Production and reserves

Workings or exploration An analysis of the molybdenite-bearing rock showed 150 ppm Mo (Koch and Elliott, 1978 [OFR 78-156A]).
Indication of production None

Additional comments

Site is on the western boundary of Misty Fiords National Monument Wilderness.

References