Trevor Matterson, MSc

T. Matterson¹, D. Petts², D. Regis², D. Moser¹, J. Czas^2 
1Earth Sciences Department, University of Western Ontario, London, Ontario, Canada
 ²Natural Resources Canada, Geological Survey of Canada, Ottawa, Ontario, Canada

The Kivalliq region in Nunavut contains banded iron formation (BIF) -hosted gold deposits, including the Meliadine and Meadowbank mines, that are being actively studied. Units of BIF northeast of Rankin Inlet (east of Meliadine) have received less attention. Our aim is to characterize the pre-mineralization states of BIF in this region as a baseline to understand metal mobilization and concentration during regional Barrovian metamorphism. The study area is in a complex transition zone between the Rae and Hearne cratons, which is affected by regional Archean and localized Paleoproterozoic deformation at greenschist to amphibolite facies conditions. The goal of this project is to gain insight into the relative timing and paragenesis of minerals in BIF that are known to carry precious metals, along with any relationships between metal mobility and tectono-metamorphic processes that would inform exploration in the region. Element maps generated by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) on representative BIF samples show low Au contents in the interior of pyrite crystals, but elevated metal contents (Au, Ag, As, Cu, Te, Bi) as well as high Ba and Ce along grain boundaries of pyrite, indicating metal mobility related to late-stage hydrothermal alteration affecting both pyrite and magnetite. Moving from south to north, BIF samples were exposed to higher degrees of metamorphism, with the southern mica-rich BIF becoming more amphibole- and garnet-rich further north. The trace element chemistry of magnetite and pyrite across metamorphic grade will be presented along with the key geochemical signatures related to primary and secondary formation processes. This work will increase the understanding of the paragenesis of BIF-hosted metals in this previously unmapped area of a geologically complex region and will be combined with additional field data to provide a pre-mineralized analogue for future exploration projects.