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Abstract

The Kwanika porphyry deposit, located in the central Canadian Cordillera, is a Late Triassic to Early Jurassic calc-alkaline copper-gold±molybdenum system exhibiting unusual platinum-group elements (PGE) enrichment across three distinct geological zones. Palladium (Pd) mineralization was first identified in 2022, with elevated Pd concentrations associated with high-grade copper-gold mineralization in the Central Zone and lower-grade Pd in the South Zone. Additionally, ultramafic rocks spatially associated with these zones contain appreciable palladium and platinum contents in the absence of copper-gold mineralization. However, the mechanisms controlling palladium and gold formation and their deportment characteristics remain poorly understood. This study aimed to determine the primary host mineral(s) for palladium and gold and investigate geological factors controlling the formation of palladium and gold. Selected samples containing copper mineralization and quartz veins were analyzed using a variety of laboratory and analytical approaches including heavy mineral separation, fire assay, scanning electron microscope, and electron probe microanalysis. Results indicate that quartz and chalcopyrite host the Pd-, Pt-, and Au-bearing minerals in the deposit. Two distinct styles of PGE mineralization were identified: Pd-dominant mineralization in the Central and South zones and Pd+Pt-dominant mineralization in ultramafic rocks. Pd-dominant mineralization occurs within monzonite and quartz monzonite host rocks, characterized by sulphide mineralization in quartz veins. It is associated with a semi-metal assemblage (Cu-Au-Ag-Pd-Te±Hg±Sb±As), with platinum group minerals (PGM) primarily located at quartz-chalcopyrite boundaries or enclosed within these minerals. In contrast, Pd+Pt-dominant mineralization in hornblende pyroxenite, with rare sulphide mineralization, is linked to a semi-metal assemblage (Pd-Pt-As-Sb±Te±Hg) and hosted by clinopyroxene, with Pd/Pt arsenides, low tellurium content, and absence of gold- and silver-bearing minerals. The findings suggest that two distinct mineralization processes occurred: The Central and South zones are characterized by semi-metal-rich melts transported by hydrothermal fluids, whereas ultramafic rocks represent a magmatic origin, crystallized directly from the melt. This study enhances the understanding of palladium and gold mineralization in the Kwanika deposit and underscores the potential for palladium recovery as a valuable critical mineral by-product in porphyry copper deposits.