Unnamed (Hulahula River)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Co; Pb; Zn
Ore minerals chalcopyrite; malachite
Gangue minerals clay; hematite; sericite

Geographic location

Quadrangle map, 1:250,000-scale ML
Quadrangle map, 1:63,360-scale A-2
Latitude 69.0657
Longitude -144.6652
Nearby scientific data Find additional scientific data near this location
Location and accuracy The location is the ridge two miles northwest of the confluence of Itkillik Creek with the Hulahula River, and about three miles south of the airstrip. This location is part of a group of copper occurrences that occur within an area that extends five miles north and south and four miles east to west. The area is in the Mount Michelson A-2 Quadrangle. The site is referred to as USGS Location 41 reported in Brosgé and Reiser, 1976, and is in the NW¼ sec. 34, T. 4 S., R. 31 E., of the Umiat Meridian. Accuracy of the location is about 0.75 mile.

Geologic setting

Geologic description

Regional potential for copper mineralization had 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 (Reiser and others, 1971) with a high intrinsic copper content, and multiple copper showings in the area. They reported a group of stream sediment samples were consistently anomalous along the upper 10 miles of the west-to-southwest flowing upper segment of the Hulahula River (Brosgé and Reiser, 1976). They believed this regional copper anomaly reflects widespread copper enrichment in mafic rock including sills.
At the USGS Location 41site, chalcopyrite was reported by Brosgé and Reiser (1976), to occur in sheared mafic volcanic rocks with individual minor malachite occurrences up to 40 feet across (Barker, 1983, and Brosgé, written commun., 1982). Samples indicate copper values are generally elevated in samples of sills. Several sites of minor malachite staining also occur in the area to the west and are associated with pyritic zones and limonite in fractured, bleached mafic volcanic rocks, and is locally associated with disseminated sulfide grains. (Note a copy of Brosgé’s written communication is available upon request from Alaska Division of Geological and Geophysical Surveys Geologic Materials Center, Anchorage, Alaska, in the archive for project files of J.C. Barker, U.S. Bureau of Mines.)
Geologic map unit (, )
Mineral deposit model The copper occurrences in mafic rocks here are similar to Besshi-type copper deposit model (Cox and Singer, 1986, model 24b).
Mineral deposit model number 24b
Age of mineralization Mineral occurrences are hosted in lower Paleozoic mafic rocks and clastic rocks of the pre-Mississippian Neruokpuk basement (Reiser, and others, 1971).
Alteration of deposit Bleaching, sericite, pyrite, and limonite staining are common features, locally with hematite staining, silicification, quartz stockwork, and minor veining (Brosgé and Reiser, 1976, and Brosgé written commun., 1982).

Production and reserves

Workings or exploration The prospect area was selected for field examination and sampling by the U.S. Bureau of Mines in 1982 as part of Alaska-wide critical and strategic mineral investigations as reported in Barker, 1983. On the basis of the previous work by Reiser and other. 1971, the contact relationships were examined for evidence of alteration and mineralization. Copper mineralization was found restricted to a zone up to 15 ft wide within the mafic rocks; minor silicification, bleaching due to argillic alteration, and traces of copper minerals were present. Although summer at the time of the examination the area was partly snow-covered.
Indication of production None

Additional comments

The area was selected for study by the U.S. Bureau of Mines in 1982 as part of Alaska-wide critical and strategic mineral investigations. The region is closed to mineral development; site is located in the Arctic National Wildlife Range and presently classified as ‘Wilderness’.

References

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