The North Fork Project is located 40 km north-west of Salmon in the Salmon‐Challis National Forest, Lemhi County, Idaho.
The North Fork Project includes 499 unpatented mining lode claims covering approximately 10,309 acres (42 km2).
The claims include historically known areas of anomalous rare earth mineralization in the North Fork ‘mineralized trend’. This mineralized trend is a north‐south oriented belt approximately 2.9 km wide and 30 km long running from the Indianola Ranger station on the Salmon River northwest into Montana.
The rare earth mineralization at North Fork is emplaced as an igneous carbonatite intrusion, hosted in ancient Proterozoic metamorphosed Belt Supergroup amphibolites and augen gneisses. The mineralization is located primarily in the carbonatite magmatic dikes and sills or “veins” with minor observed secondary porphyry overprinting and alteration.
The geologic history of the area is complex as many faults, igneous intrusions, and late Cenozoic volcanism intersect on the North Fork Project properties. Mineralization is inferred to be associated with a, as yet unidentified, subsurface syenite‐peralkaline intrusion located in the area.
The North Fork Project veins are structurally controlled (emplaced along faults, fractures, and foliation) and have been historically shown to be associated with some niobium and minor thorium mineralization (Avg. less than 165 ppm thorium). Detailed mineralogy is the subject of this current investigation; however, historical data suggests the important mineralogy is principally monazite and allanite with minor amounts of other associated rare earth minerals.