Alces Lake, Saskatchewan, Canadai

Regional Level Types
Alces Lake	Deposit
Saskatchewan	Province
Canada	Country

Alces Lake is ranked by grade for containing the highest-grade REE occurrences in Canada and the second highest in the world after the Gakara Rare Earth Elements (REEs) deposit. Currently, the Alces Lake tonnage is unknown, as there is no preliminary NI-43-101 resource estimate. The REE in most of the high-grade zones are hosted mainly in monazites (locally the monazite content reaches up to 85 modal %,) within quartzo–feldspathic granitic to biotite–garnet–monazite–zircon-rich restite-bearing/cumulate mush partial melt pegmatites. The REE mineralogy of the low- to medium-grade zones (low-grade mineralization is 0.1 to 1.0 wt.% TREO (total rare earth oxides), medium-grade mineralization is 1.0 to 4.0 wt.% TREO, and high-grade mineralization > 4.0 wt.% TREO. The REE-bearing pegmatites are associated spatially with regional- to district/camp-scale fold structures, ductile shear zones, and brittle faults, with the latter two structures cutting both paragneiss and orthogneiss.
The REE mineralized system is composed of Proterozoic late-orogenic to metasomatic massive braided biotite schist, quartzofeldspathic pegmatite augen, and monazite accumulations. In outcrop, the mineralization is unique and enigmatic. Most of the REE in the high-grade mineralized zones (e.g., the Wilson and Ivan zones) are hosted primarily within monazites, and to a lesser degree in allanite, xenotime, and apatite, within both the biotite schists (glimmerites) and pegmatite augens. The monazite mineralization occurs in different habits from isolated grains within 1 to 3 cm thin lenses, as isolated massive clusters up to meters thick, and as pervasive massive clusters of monazite in augenitic (boudinaged) masses along ductile to ductile/brittle to brittle structures.

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References