Kokrines-Hodzana REE

Region Alaska, Alaska
Mineral systems
Deposit types
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Data-driven prospectivity ranking of watersheds (HUCs; Karl and others, 2016) shows that the focus area includes 31,760 km2 with a total of 100 HUC's having high prospectivity. The belt is a regional REE geochemical anomaly, with favorable alkaline, calc-alkaline, and peraluminous lithologies represented by the Ruby batholith and associated intrusions. Alluvial deposits, containing widespread concentrations of REE, tin, tungsten, zirconium ± niobium, and tantalum heavy minerals, are primarily derived from granitic source rock of the Ruby batholith, and are most abundant in the lower elevation terrain between the Ray Mountains and the northern Fort Hamlin Hills.
Identified resources None.
Production None recorded.
Status Current exploration in the Ray Mountains area: Industry has an active exploration program attempting to find the lode sources in the alkaline to peralkaline Ruby batholith.
Estimated resources Unknown.
Geologic maps Approximately 10% of the belt is mapped at 1:63:360 scale or better. Most maps located in the northernmost extent of the belt.
Geophysical data Inadequate aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Ruby batholith composed of monzonite and syenite is exposed over approximately 60% of the recognized belt. Total lithology scores range from 0-1, of which igneous scores range from 0-4. Calc-alkaline, alkaline, peraluminous intrusive rocks of the Ruby batholith. The batholith is made in part of the Sithylemenkat, Ray Mountains, and Melozitna plutons which all host REE-bearing, tin-bearing veins, and tin greisen assemblages.
Deposits None.
Evidence from mineral occurrences Known placer occurrences are associated with granite-related Sn mineralization in the central portion of the belt; Local placers are identified in ARDF in the Ray Mountains. ARDF scores range from 0-2 ARDF: TN141.
Geochemical evidence Sediment geochemistry scores range from 3-6, and average 5.53 points. Industry reports Ruby batholith alluvial geochemical data, which shows ΣREE+Y ranging from 1-973 g/m3 in alluvial samples.
Geophysical evidence Aeroradiometric scores range from 0-1 and average 0.58.
Evidence from other sources No data.
Comments Ruby batholith exhibits alkaline to peralkaline geochemical compositions and is associated with a number of granite-related (greisen) tin occurrences with known byproduct LREE enrichments. The region has not been systematically evaluated for alkaline REE mineralization. Numerous tin placer occurrences throughout the Ray Mountains show strong REE enrichments, and are typically localized around more alkaline plutons within the Ruby batholith. Active exploration is attempting to delineate lode and detrital resources of REE. Also contains uranothorite.
Cover thickness and description Unknown.
Authors Douglas C. Kreiner, James V. Jones III, Melanie B. Werdon.
New data needs New mapping, geophysics, updated geochemical sampling.
Geologic mapping and modeling needs Framework geology-including mapping of lithology, structure, and hydrothermal alteration; characterization of igneous phases, petrogenesis, and structural setting; hydrothermal assemblages, geochronology, and structural data. Isotopic data (Hf, Pb) needed to test crustal character and terrane affinity. In the Ray Mountains area, systematic, detailed geologic mapping is needed of the quadrangles containing and surrounding ARDF records and possible igneous lode source throughout the region to understand their petrogenesis and tectonic setting. A better understanding of hydrothermal assemblages to characterize mineral systems and correctly place them into mineral systems framework. Isotopic data (Hf, Pb) of all igneous phases is needed to test crustal character and terrane affinity.
Geophysical survey and modeling needs Rank 1 or 2 aeromagnetic data over the entire belt. Targeted EM where relevant for lithologic and structural mapping under cover.
Digital elevation data needs IfSAR coverage is complete over entire focus area.