Banded Iron Formation-Associated Gold Deposit

Focus : Eeyou Istchee James Bay, Nunavik and Nunavut

Several major gold deposits in Nunavut, Ontario and Quebec are associated with banded iron formations, which are iron-rich (≥15 wt.% Fe) sedimentary units in submarine volcano-sedimentary sequences. While iron-rich strata may be slightly enriched in trace metals produced by submarine volcanism and hydrothermal activity, the gold deposits contained in these units are epigenetic, meaning they are significantly younger than the host rocks. The presence of gold is due to the circulation of hydrothermal fluids generated at depth in the Earth’s crust during deformation, where an increase in the thermal gradient (metamorphism) liberates fluids and gold. While the geometry of the deposits associated with iron formations can be particularly complex, complicating exploration and mining in some cases, iron formations are attractive exploration targets in remote areas due to their potential to host high-grade and high-tonnage gold deposits.

This article provides an overview of the main characteristics of banded iron formation-associated gold deposits (hereinafter “BIF-Au” for simplicity).