Anastasiia Mashkova, MSc
A. Mashkova1, S. Brueckner1, S. Piercey2, D. Layton-Matthews3
1Harquail School of Earth Science, Laurentian University, Sudbury, ON, Canada
2Department of Earth Sciences, Memorial University of Newfoundland, St. John’s, NL, Canada,
3Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON, Canada
Volcanogenic massive sulfide (VMS) deposits are significant sources of base and precious metals and are increasingly recognized for their critical metal potential including Bi, Ni, Co, Sb, and Te. However, their occurrence and behavior during metamorphism and deformation remains poorly understood. This project aims to address this gap by investigating the mineralogical and chemical characteristics of critical metals in VMS deposits metamorphosed from greenschist to upper amphibolite facies.
Preliminary work on the Neoproterozoic Genex deposit, Ontario focused on ore assemblages and textures in both stockwork and (semi-)massive sulfide zones. The Genex deposit is a VMS system hosted in felsic and mafic volcanic and volcaniclastic units. It has experienced greenschist facies metamorphism during the Late Archean Algoman orogeny. The deposit was mined between 1964 and 1966, producing approximately 242 tons of copper concentrate from two primary orebodies, the C and H zones. Historical indicated resources are 214,000 t at 1.68 % Cu.
Reflected light microscopy indicates that massive and semi-massive zones that are enriched in chalcopyrite exhibit the most diverse mineralogical assemblages. Chalcopyrite is the dominant sulfide phase, forming massive aggregates and intergrowths with sphalerite, pyrite, and trace amounts of sulfosalts (assumingly enargite), arsenopyrite, tellurides and electrum. Sphalerite shows chalcopyrite disease, with fine-grained disseminated chalcopyrite. Pyrite textures reveal spongy structures and partial replacement by chalcopyrite. Additionally, pyrite shows deformation-related features such as cataclasis and triple junctions. Of the critical metal-bearing phases besides chalcopyrite and sphalerite, assumed sulfosalts and tellurides show a variation of complex textures including fracture filling in chalcopyrite, sulfosalt rims forming around unknown phases, intergrowth of tellurides and unknown phases.
Whole rock lithogeochemistry on massive sulfide and stringers show enrichment in critical metals such Bi (up to 250 ppm), Co (up to 770 ppm), Te (up to 82 ppm), and Ni (up to 264 pm) besides Cu (>10,000 ppm) and Zn (>10,000 ppm).
Future work will constrain the composition of base metal sulfides, sulfosalts, and critical metal-bearing phases (e.g., tellurides) using electron probe microanalysis and laser ablation inductively coupled plasma mass spectrometry with emphasis on their critical metal content. Refining the textural relationship between the different phases and identifying microstructure using scanning electron microscopy and electron back-scattered diffraction, respectively will complement this work.