Unnamed (near Ipnavik River)

Occurrences, Probably inactive

Commodities and mineralogy

Main commodities Ag; Cu; Pb; Zn
Ore minerals chalcopyrite; galena; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale HW
Quadrangle map, 1:63,360-scale B-3
Latitude 68.3631
Longitude -157.351
Nearby scientific data Find additional scientific data near this location
Location and accuracy These occurrences are about 0.8 mile east of peak 1143 (in meters) and about 3.7 miles south-southwest of the mouth of Friendly Creek on the Ipnavik River. They are about 0.5 mile northwest of the center of section 7, T. 34 N., R. 7 E.

Geologic setting

Geologic description

The rocks in the area are Upper Devonian to Lower Mississippian, Kanayut Conglomerate, Noatak Sandstone, and Kayak Shale that are in both stratigraphic and fault contact. The rocks have been folded into a southwest plunging anticline that is exposed in a window through a thrust fault whose upper plate is Noatak Sandstone and Kanayut Conglomerate.
At the most prominent area of mineralization, massive layers, stringers, and disseminated galena and minor sphalerite and chalcopyrite occur in silicified and brecciated Noatak(?) sandstone just above a siltstone that may be part of the Kayak Shale or Noatak Sandstone (Kurtak and others, 1995). Near the mineralization, the sandstone is brecciated and silicified, giving the rocks a bleached appearance. Samples from an area about 3 meters by 92 meters in size contained up to 36 percent lead, 4 percent zinc, and 439 grams of silver per tonne. A representative chip sample across a 2-meter-wide zone of rubblecrop contained 9.5 percent lead and 140 grams of silver per tonne. A sample of apparently barren, silicified sandstone about 10 meters from the sulfide-bearing sandstone contained 1,466 parts per million (ppm) lead and 1,526 ppm zinc. Several other samples of bleached sandstone collected in an area about a mile long also contained anomalous lead and zinc. An isotopic analysis of galena gave the following values: Pb 206/204 = 18.482; Pb 207/204 = 15.586, and Pb 208/204 = 38.233. These values indicate a Mississippian model age which is comparable to other Mississippian shale-hosted deposits and vein occurrences in Devonian sandstone and conglomerate in the western Brooks Range.
Geologic map unit (-157.353941339175, 68.3625806575565)
Mineral deposit model Sandstone lead-zinc deposit?
Age of mineralization Probably Mississippian based on lead isotope analyses.
Alteration of deposit The sandstone near the mineralization is silicified, brecciated, and bleached.

Production and reserves

Workings or exploration Only sampling by the U.S. Bureau of Mines.
Indication of production None
Reserve estimates None.
Production notes None.

Additional comments

MAS number 0020200024.

References