Unnamed (Hulahula River) USBM Location B

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Co; Ni; Pb; Zn
Ore minerals chalcopyrite; malachite
Gangue minerals clays; limonite; hematite

Geographic location

Quadrangle map, 1:250,000-scale ML
Quadrangle map, 1:63,360-scale A-2
Latitude 69.0822
Longitude -144.5457
Nearby scientific data Find additional scientific data near this location
Location and accuracy Location B is in rugged mountainous terrain about two miles east-southeast of the airstrip on the Hulahula River and Location A of Barker (1983). Hulahula River flows north to the Arctic Ocean and is headwaters drain the north flank of the Continental Divide. The occurrence site is referred to as Location B (Barker, 1983) situated above the 5000 foot contour level. The site is in the SW1/4, sec. 24, T. 4 S., R. 31 E., of the Umiat Meridian. Accuracy of the location is about 0.75 mile.

Geologic setting

Geologic description

Location B is hosted in pre-Mississippian clastic rocks and mafic sills cutting a sequence of green and brown argillite (Reiser and others, 1971).
U.S. Bureau of Mines samples 19059-60 at Location B occur near the ridgetop and exhibit minor copper mineralization at the contact of green and brown argillite (Barker, 1983). Intermittent snow cover at the time of the examination precluded definitive contact relationships. It was uncertain if the green argillite(?) may have actually been a highly altered mafic rock. Samples 19059 and 19060 from a shear zone with spotty malachite assayed 405 and 1700 parts per million (ppm) copper, respectively. Elevated silver, cobalt, and nickel were also present. Thinly bedded, foliate dolostone that outcrops at sample 19104 near this location also contained finely disseminated sulfide grains that included trace to minor chalcopyrite; a sample assayed 334 ppm copper.
Favorability for regional copper potential has been advanced by Brosgé and Reiser (1976) who suggested that the vicinity of the upper Hulahula River is favorable for copper mineralization due to widespread mafic volcanic rocks with high intrinsic copper content; several copper showings were reported in the region. A group of stream sediment samples were also consistently anomalous along the upper 10 miles of the Hulahula River (Brosgé and Reiser, 1976).
Geologic map unit (, )
Mineral deposit model Besshi-type copper (Cox and Singer, 1986, model 24b).
Mineral deposit model number 24b
Age of mineralization Mineral occurrences appear to be hosted in rocks of the pre-Mississippian clastic rocks and mafic sills of the Neruokpuk Formation (Brosgé and Reiser, 1976).
Alteration of deposit Bleaching and iron staining are common features in the area, limonite in shear zone locally with hematite staining and silicification, minor quartz stockwork and veining. Pyritic quartz carbonate mineralized zone cuts the host rock (J.C. Barker, unpublished data).

Production and reserves

Workings or exploration U.S. Bureau of Mines samples 19059-60 at Location B occur near the ridgetop and exhibit minor copper mineralization at the contact of green and brown argillite (Barker, 1983). It was uncertain if the green argillite(?) may have been a highly altered mafic rock. Samples 19059 and 19060 from a shear zone with spotty malachite assayed 405 and 1700 parts per million (ppm) copper, respectively. Elevated silver, cobalt, and nickel were also present. Thinly bedded, foliate dolostone that outcrops at sample 19104 near this location also contained finely disseminated sulfide grains that included trace to minor chalcopyrite; a sample assayed 334 ppm copper.
Indication of production None

Additional comments

The prospect area was selected for study by the U.S. Bureau of Mines in 1982 as part of on-going critical and strategic mineral investigations in Alaska. No further work was performed. The area is now closed to mineral development; the site is located in the Arctic National Wildlife Range and classified as Wilderness.

References

Reporters J.C. Barker
Last report date