The Mary River Group (MRG) refers a suite of Neoarchean supracrustal rocks within greenstone belts of the Rae Craton of northern Baffin Island (Saumur et al, 2025). The MRG hosts the high grade, high-tonnage Mary River Fe-ore deposits, which were discovered in the early 1960s. Renewed exploration efforts, feasibility studies and public consultations in the mid-2000s led to open pit mining ore production at Deposit 1 starting in 2014 (Iannelli, Dammeier and Samiei, 2016). Iron ore grades that average 63–65 wt per cent Fe allow for direct shipping to market without concentration or processing (Baffinland Iron Mines, 2026). This, as well as the sheer size of the deposits (roughly 1 billion tonnes (Bt) of Measured, Indicated and Inferred Mineral Resources; ArcelorMittal, 2024), renders Mary River economic despite challenging logistics associated with remote Arctic operations. As of 2026, Mary River’s Deposit 1 is the site of Canada’s northernmost active mine, and accounts for 9 per cent of Canada’s total Fe production (NRCan, 2025) and 4.2 million tonnes (Mt) of shipped ore per annum. Recent field studies have elucidated some of the important geological ore-forming controls at play at Mary River. We highlight those herein, as well as new geochronological information about ore formation.