Unnamed (south of lake 780)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Zn
Other commodities Cd; W
Ore minerals hematite
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale A-1
Latitude 61.04535
Longitude -156.01679
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is near the top of the isolated knob, hill 1333, about 0.7 mile south-southeast of lake 780. The occurrence is about 0.4 mile east-northwest of the center of section 16, T. 11 N., R. 38 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence is a zone of hematite-rich quartz veins in fine-grained hornfels derived from what has been mapped as the Upper Cretaceous Kuskokwim Group (Cady and others, 1955; LePain and others, 2000). The protolith might also be the Kahiltna assemblage (Wilson and others, 1998). A high level, aphanitic rhyolite intrusive body underlies the hornfels (M. L. Miller, unpublished field data, 1999). Hematite locally makes up a large percentage of the quartz vein. Three grab samples collected of the hematite-rich quartz vein contained up to 2.88 parts per million (ppm) cadmium, 795 ppm zinc, and 14.5 ppm tungsten (M. L. Miller, unpublished analytical data, 1999).
Geologic map unit (-156.019081238369, 61.0446602913031)
Age of mineralization Unknown. The rhyolite body under this occurrence has a 40Ar/39Ar age of 67 Ma (R. Wilson, oral communication, 2003).
Alteration of deposit Hematite replacement in hornfels.

Production and reserves

Workings or exploration The U.S. Geological Survey sampled the site in 1999.
Indication of production None

References