Unnamed (Hulahula River) USBM Location C

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Co; Pb; Zn
Ore minerals chalcopyrite
Gangue minerals clays; hematite; pyrite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale ML
Quadrangle map, 1:63,360-scale A-1
Latitude 69.0447
Longitude -144.5915
Nearby scientific data Find additional scientific data near this location
Location and accuracy
The location given is near the confluence of the Hulahula River and Itkillik Creek. This location is part of a group of copper occurrences found over an area five miles north-south and four miles east-west.
Hulahula River flows north to the Arctic Ocean and its headwaters drain the north flank of the Continental Divide. The occurrence site is referred to as U.S. Bureau of Mines Location C (Barker, 1983) and is in the NW¼, sec. 5, T. 5 S., R. 32 E., of the Umiat Meridian. Accuracy of the location is about 0.75 mile.

Geologic setting

Geologic description

Favorability for regional copper mineralization has been advanced by Brosgé and Reiser in 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 consistently anomalous along the upper 10 miles of the upper segment of the Hulahula River (Brosgé and Reiser, 1976), which is underlain by widespread mafic rocks (Reiser, 1971) that may have acted as a source for copper remobilized into favorable nearby rocks or structural traps.
At Location C strata bound style mineralized copper occurrences occur in the Kekiktuk Conglomerate. Conglomerate boulders with quartz stockwork and infrequently with chalcopyrite occur in the lower Itkillik Creek at Location C. A chip sample assayed 1.86 percent copper. A second sample of another group boulders assayed 0.135 percent copper. Both contained elevated silver. The bedrock source was not found; however Brosgé and Reiser (1976) also reported chalcopyrite in brecciated and schistose quartzite, chert, and quartz pebble conglomerate and sandstone of the Kekiktuk Conglomerate at their location 42 (69.0150 N, 144.6657 W), and at their location 43 (69.0347 N, 144.5242 W) chalcopyrite occurs in conglomerate and phyllite that is interbedded with chert and mafic volcanic rocks.
Geologic map unit (, )
Mineral deposit model Besshi-type copper (Cox and Singer, 1986, model 24b); sedimentary-hosted copper (Cox and Singer, 1986, model 30b).
Mineral deposit model number 24b, 30b
Age of mineralization Mineral occurrences are hosted in rocks of the Mississippian clastic rocks of the Kekiktuk Conglomerate (Brosgé and Reiser, 1976).
Alteration of deposit Bleaching and iron staining are common features, locally with hematite staining and silicification, quartz stockwork and minor veining (Barker,1983).

Production and reserves

Workings or exploration At Location C strata bound style mineralized copper occurrences occur in the Kekiktuk Conglomerate. Conglomerate boulders with quartz stockwork and infrequently with chalcopyrite occur in the lower Itkillik Creek at Location C. A chip sample assayed 1.86 percent copper. A second sample of another group boulders assayed 0.135 percent copper. Both contained elevated silver. The bedrock source was not found; however Brosgé and Reiser (1976) also reported chalcopyrite in brecciated and schistose quartzite, chert, and quartz pebble conglomerate and sandstone of the Kekiktuk Conglomerate at their location 42 (69.0150 N, 144.6657 W), and at their location 43 (69.0347 N, 144.5242 W) chalcopyrite occurs in conglomerate and phyllite that is interbedded with chert and mafic volcanic rocks.
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. Closed to mineral development, site is located in the Arctic National Wildlife Range and classified as Wilderness.

References

Reporters J.C. Barker
Last report date 4/6/2017