Characteristics and Origin of Rare Earth Mineralization at the Alces Lake Property, Northern Saskatchewan
Date
2023-01-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0001-5855-3028
Type
Thesis
Degree Level
Masters
Abstract
Rare earth elements (REEs) are critical metals that are essential to the low-carbon economy, especially the rapidly-growing green energy production and storage industry. REEs have been produced from a great variety of deposit types related to magmatic, metamorphic, hydrothermal, chemical weathering, and sedimentary processes. Massive monazite mineralization at the Alces Lake REE property in the Beaverlodge Domain of the Rae Province of northern Saskatchewan has attracted recent exploration and has been suggested to represent a paleo-placer type deposit, which would imply significant resources; however, this interpretation for the origin of the REE mineralization is questionable.
The massive monazite mineralization at the Alces Lake property is situated on the eastern limb of a fault truncated synform fold. This synform fold is likely related to the nearby St. Louis Fault adjacent to an unconformity with Archean aged or Arrowsmith Orogeny-related gneisses and granites on the western limb and younger Paleoproterozoic gneisses and granites alongside the Murmac Bay Group metasedimentary rocks, metavolcanics, and quartzite on the eastern limb (Normand, 2014). The REE showings occur as monazite-biotite-mineralized pegmatites, massive biotite pegmatites, granitic pegmatites, allanite-rich veinlets, and large leucogranite bodies scattered throughout the property.
The REE mineralization at the Alces Lake property is primarily in the form of monazite, zircon, and allanite. The elevated REE contents largely correspond to an increase in radioactivity caused by the thorium contents in monazite and allanite. Therefore, radioactivity can be used as an exploration tool to locate REE mineralization. Exceptions to this do occur with some less radioactive pegmatites and leucogranites containing high total REE contents (>1.5 wt.%), whereas some highly radioactive biotite-rich pegmatites have <0.5 wt.% of total REE.
Field and petrographic examinations show that the Ivan-Dante Zone has a semi-continuous pegmatite of abundant monazite and zircon with the highest discovered radioactivity and REE mineralization at the Alces Lake property. Monazite-(Ce) is characterized by 5.43-10.54 wt.% ThO2, incorporated largely by the substitution Th4+ + Ca2+ = 2REE3+, while zircon contains 1.03-1.48 wt.% HfO2. U-Pb geochronological analyses yielded an age of 1926±3 Ma for zircon and 1926±15 Ma for monazite, which confirm their crystallization during the Taltson Orogeny.
Therefore, the Alces Lake pegmatite-hosted REE mineralization is not a placer, but most likely had a late magmatic-hydrothermal origin related to Taltson-aged leucogranites. The leucogranites most likely formed from anatexis as a result of granulite-facies regional metamorphism during the Taltson Orogeny and were evolved to produce pegmatites and associated hydrothermal veins containing REE mineralization. The fold hinges and faults at Alces Lake provided the conduits for focused emplacement of the REE-mineralized pegmatites and hydrothermal veins.
Description
Keywords
Alces Lake, Geology, REE, Pegmatites, Pegmatite, Monazite, Zircon, LA-ICP-MS, Geochronology, Beaverlodge Domain, Northern Saskatchewan
Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geology