Bentzen, and 6 co-authors, of the Tetra Tech Group, reported in 2013 that the Bokan Mountain Project, located southwest of Ketchikan, Alaska, will be a 1,500 t/d underground mining operation. Mineralized material will be processed in a material sorting and leaching process plant, coupled with an advanced separation process to directly produce saleable rare earth oxide (REO) concentrates. The Project is 100% owned by Ucore Rare Metals Inc. (Ucore). In 2011, Ucore commissioned a team of engineering consultants to complete a preliminary economic assessment (PEA) in accordance with National Instrument 43- 101 (NI 43-101).
A brief discussion of the geology by the authors of this engineering report indicated that the Bokan Mountain lies within the Alexander Terrane of the Canadian-Alaskan Cordillera. The Cordillera is generally considered to be a collage of allochthonous oceanic and pericratonic terranes that were accreted to the western margin of the North American craton during the Mesozoic.
The Alexander Terrane is a composite terrane which does not show any evidence of an early relationship with the western margin but instead, geological data suggest that it originates far from western North America (Laurentia) and was only transported into the Cordilleran realm by later tectonic processes The Alexander Terrane underlies most of southeastern Alaska and parts of western BC and southwestern Yukon. It is an arc terrane composed of late Proterozoic to Triassic mafic to felsic volcanic rocks, terrigenous clastic and carbonate rocks and early Paleozoic and rare Mesozoic granitic rocks.
The pre-Devonian rocks were formed in a subduction-related environment. The terrane was amalgamated with another exotic terrane—Wrangellia—some 310 Ma forming the Insular Superterrane which was subsequently accreted onto the western margin of the North American craton by the Cretaceous
(approximately 115 to 95 Ma).
Bokan Mountain represents an unusual style of REEs, uranium, niobium, and zirconium mineralization hosted within, or proximal to, a circular Jurassic A-type peralkaline intrusive complex known as the Bokan Mountain Granite. The high-level intrusion contains several concentrically zoned intrusive phases of sodic granites, porphyries and pegmatites. Aegerine and riebeckite are the dominant ferromagnesian minerals. Intense wall-rock replacement/alteration by albite, chlorite, calcite, fluorite, and hematite accompanied the mineralized material -forming processes and mineralization. Mineralization as veinlets, disseminations or as irregular sublinear masses is hosted within, or in proximaty to, the Bokan Mountain Granite and was derived from magmatic mineralized material fluids.
There are several types of uranium-thorium-REE mineralization, the most important of which are:
• irregular structurally-controlled pipes
• shear zone-related pods or lenses (veins)
• pegmatitic or felsic dikes.
The type three felsic dykes or “vein dykes” are the predominant mineralization type in the Dotson Zone, which is the current exploration target on the Property and the subject of this report. These vein dykes form a zone of potentially economic mineralization approximately 50 m wide and 2,100 m long, striking west-northwest and dipping steeply to the north. They range in thickness from a few millimeters to tens of centimeters and contain niobium, tantalum, beryllium, zirconium and REEs (both light and heavy REEs). Niobium and tantalum are present chiefly in euxenite and columbite while REEs are contained in thalenite, bastnaesite, xenotime and monazite.
[Note: Allanite is mentioned on pp. 7-17, 7-19, 13-5 to 7].
Recent Listing: https://ucore.com/docs/PEA.pdf
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