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TitleBanded iron formation-associated gold deposits
AuthorMercier-Langevin, P; Dubé, B
SourceResources, Mines and Industry 2022 p. 22-31
LinksOnline - En ligne
Alt SeriesNatural Resources Canada, Contribution Series 20210359
PublisherGroupe Tertio Inc.
Mediapaper; on-line; digital
File formatpdf
Subjectsiron formations; gold
Illustrationsphotographs; diagrams; schematic representations
ProgramTargeted Geoscience Initiative (TGI-6) Ore systems
Released2022 06 18
AbstractSeveral 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. This gold-bearing fluid is transported higher in the crust and preferentially channelled through conduits and structural traps (e.g., faults, folds and dilatational zones), where the chemistry of the iron formations, which are particularly reactive to the fluids, causes destabilization and precipitation of the gold in solution. Given that this process is closely related to tectonism and the deformation and metamorphism of rocks at different scales, these deposits belong to a category of gold deposits defined as orogenic. 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.
Summary(Plain Language Summary, not published)
This contribution summarizes the main geological characteristics of gold deposits that are associated with iron-rich sedimentary rock units called banded iron formations; an auriferous mineralization style that is common in Canada.

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