Western and central Brooks Range (Brooks Range zinc belt)

Region Alaska, Alaska
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Presence of a world-class Pb-Zn clastic-hosted deposit at Red Dog, numerous additional satellite deposits and clusters of similar styles of mineralization along an approximately 75 km east-west trend in the Northern Brooks Range. This belt is also highlighted by prospectivity analyses relying on favorable stratigraphy and geochemical signatures of sediments and rocks.
Identified resources Identified resources for gold, lead, silver, and zinc. Current and historical production of gold, lead, silver, and zinc.
Production Red Dog is in active production, historical production variable by district.
Status Past and current mining and exploration.
Estimated resources Red Dog: 84.9 M short tons @ 3.7% Pb, 12.2% Zn, 2.01 oz/t Ag; Anarraaq: 21.4 M short tons @ 4.2% Pb, 14.4% Zn, 2.13 oz/t Ag.
Geologic maps Statewide geologic map database; Wilson, Hults and others (2015), scale 1:1,584,000.
Geophysical data Mostly (>90%) inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Zinc belt: Carbonaceous mudstone and shale of the Mississippian Kuna Formation of the Lisburne Group. Additionally, Upper Devonian to Lower Mississippian Endicott Group hosts multiple breccias and small, high-grade veins. These are believed to represent feeders for fluid flow. Bairds Mountains: Ordovician through Devonian Baird Group carbonate rocks.
Deposits Red Dog, Anarraaq, Drenchwater.
Evidence from mineral occurrences ARDF occurrences including Red Dog, Drenchwater, and Anarraaq cluster.
Geochemical evidence Sediment and panned concentrate samples contain Ag, Ba, Pb, and Zn anomalies well above background. Locally, where data are available, anomalous In has been noted in the belt. Rock samples contain elevated Ag, Ba, Pb, Zn with isolated Cu, Ge, In, and Tl anomalies.
Geophysical evidence No data.
Evidence from other sources Prospectivity analysis for sediment hosted Pb-Zn deposits delineates the belt as having moderate and high prospectivity (Kelley and others, 2021).
Comments These belts contain the world class Red Dog deposit, in addition to a number of smaller known deposits with identified resources. Evidence of fluid flow is observed all along the belt which extends for more than 75 km in an east-west swath across the Brooks Range.
Cover thickness and description Unknown.
Authors Douglas C. Kreiner, James V. Jones, III.
New data needs New mapping, geophysics, updated geochemical sampling with a focus on increasing trace element datasets for Ge, In and other critical minerals.
Geologic mapping and modeling needs Mapping at 1:100,000 scale or better.
Geophysical survey and modeling needs Aeromagnetics and radiometrics collected at Rank 2.
Digital elevation data needs IfSAR coverage is complete over entire focus area.