Occurrence, Inactive

Commodities and mineralogy

Main commodities Zn
Ore minerals pyrite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale MG
Quadrangle map, 1:63,360-scale A-2
Latitude 62.224
Longitude -153.827
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is exposed in outcrops on the south bank of a prominent, unnamed eastern fork of Windy Fork at an elevation of 3,100 feet (945 m) in the SW1/4 sec. 25, T. 25 N., R. 25 W., of the Seward Meridian. The reporter visited the site in 1982.

Geologic setting

Geologic description

This occurrence is a stratiform sulfide zone in the Lower Ordovician to Lower Silurian Post River Formation, a unit of the Dillinger subterrane (Bundtzen, Harris, and Gilbert, 1997). The sulfide bearing zone is estimated to be about 1.5 meters thick and consists of several thin pyritiferous layers with traces of sphalerite observed (Bundtzen and others, 1988). Two chip samples taken across 3 meters of the sulfide-bearing shale averaged 395 ppm zinc.
Geologic map unit (-153.829221237353, 62.2233820048939)
Mineral deposit model Sedimentary exhalative lead zinc? (Cox and Singer, 1986; model 31a).
Mineral deposit model number 31a?
Age of mineralization Inferred to be Late Ordovician to Early Silurian.

Production and reserves

Workings or exploration Kristi McDonald of the Alaska Division of Geological and Geophysical Surveys found and sampled the occurrence in 1982 while measuring section in the Lower Paleozoic black shales of the Post River Formation (Churkin and Carter, 1996). Two chip samples taken across 3 meters of the sulfide-bearing shale exposure averaged 395 ppm zinc (Bundtzen and others, 1988).
Indication of production None
Reserve estimates None.

Additional comments

See unnamed stratiform occurrence at site MG071.