The role of metamorphic and geochemical factors in the formation of gem corundum, spinel, and haüyne in metacarbonates of the Lake Harbour Group, Baffin Island, Canada ...

• Main Author: Belley, Philippe Maxime
• Format: Text
• Language: English
• Published: University of British Columbia 2019
• Subjects: Baffin Island; Baffin
• Online Access: https://dx.doi.org/10.14288/1.0378174; https://doi.library.ubc.ca/10.14288/1.0378174

The Lake Harbour Group (LHG) metacarbonates on Baffin Island contain occurrences of the gemstones sapphire (corundum), spinel (including cobalt-blue), and lapis lazuli (blue haüyne-rich rock). This dissertation uncovers the regional geologic processes (e.g., metamorphic history, metasomatism, protolith geochemistry) that influence gemstone potential by developing genetic models for the LHG gem mineral occurrences. Both barren and gem-bearing metacarbonates were studied using field examination and sampling, petrological (optical) and scanning electron microscope petrography, and whole rock geochemistry. Boron isotope geochemistry, thermodynamic modelling, and age-dating (zircon U-Pb and mica ⁴⁰Ar-³⁹Ar) were employed for selected occurrences. Corundum formation was made possible by three equally important sequential metamorphic reactions: (1) formation of nepheline, diopside, and K-feldspar (inferred) at granulite facies peak metamorphic conditions; (2) partial retrograde replacement of the peak assemblage by ...