Farewell Terrane

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

Information leading to the delineation of this focus area

Basis for focus area Mineral occurrences described as clastic-dominated Pb-Zn deposits that occur in favorable lithologies, however these deposits are poorly studied. The presence of massive bedded barite suggests fluid flow of appropriate characteristics through the favorable lithology. The belt is highlighted by prospectivity analyses.
Identified resources Identified resources for barite and zinc.
Production None recorded.
Status Past exploration.
Estimated resources Gagaryah: 2.3 Mt @ 57% barite; Reef Ridge: 1.9 Mt @ 6.5% Zn.
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 Occurrences are hosted in the Ordovician to Silurian Post River Formation, which consists of limestones and shales.
Deposits Gagaryah, Reef Ridge.
Evidence from mineral occurrences ARDF occurrences including the Gagaryah and Reef Ridge.
Geochemical evidence Sediment and panned concentrate samples contain Ag, Ba, Pb, and Zn anomalies well above background. Rock samples contain elevated Ag, Ba, Pb, Zn with isolated Co, Cu, Ge, In, and Tl.
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 While this region is also known to contain numerous skarn occurrences, the prospectivity analysis attempts to remove those from the results through careful consideration of lithology and ARDF descriptions. The region remains prospective for basin brine path Pb-Zn mineralization.
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 others.
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.