Linking Magmatism and Gold Mineralization at the Fenelon Gold Deposit, Northern Abitibi, Canada: Insights from Pyrite Chemistry, U-Pb and Re-Os Geochronology

Abstract

The Fenelon gold deposit, located in the underexplored northern region of the Abitibi greenstone belt, hosts an estimated 4.09 Moz at 3.20 g/t Au and is spatially associated with the 2697 ± 0.96 Ma Jeremie diorite (isotope dilution-thermal ionization mass spectrometry [ID-TIMS] U-Pb zircon). Gold mineralization at Fenelon consists of two styles: shear hosted and vein hosted. The Tabasco-Cayenne zones typically occur as an anastomosing shear system, whereas the Area 51 zone contains parallel sheeted veins that range from sulfide-poor quartz veins to sulfide-rich, base metal-bearing veins. Ore petrography and pyrite geochemistry reveal three distinct pyrite generations, each reflecting evolving fluid conditions. Pyrite 1 (Py1) and pyrite 3 (Py3) are relatively enriched in Co and Ni but depleted in Cu, Zn, and Au, whereas pyrite 2 (Py2) exhibits zoning and elevated base and precious metal concentrations, which are more characteristic of intrusion-related, magmatic-hydrothermal deposits than classic orogenic gold systems. Rhenium-osmium dating of molybdenite from a gold-bearing vein crosscutting the Jeremie diorite yielded an age of 2710 ± 11 Ma, indicating that gold mineralization coincided with the prolonged emplacement of the Jeremie Suite between 2710 and 2697 Ma. We propose that mineralization was driven by magmatic-hydrothermal fluids derived from the Jeremie diorite, which contributed to gold endowment. This study highlights the role of pyrite chemistry in discriminating fluid sources and supports an intrusion-related model for gold mineralization at Fenelon.