Deposits of this type are characterized by an abundance of magnetite and/or hematite in tabular bodies (Kiruna), breccia-fillings (Olympic Dam), veins, disseminations and replacements, all in continental, dominantly felsic volcano- plutonic settings in a late tectonic or anorogenic environment. The host rocks include all volcanic lithofacies ranging from proximal, epizonal feeder systems to distal volcaniclastic sediments, and related epizonal plutons. The deposits range from essentially monometallic (Fe) to polymetallic (Fe+Cu±U±Au±Ag±REEs). Large monometallic deposits have been mined for iron alone, but in polymetallic deposits associated metals are at the main economic interest.

The largest and most important examples occur outside Canada; these include the classic magnetite-apatite-actinolite deposits of the Kiruna district in northern Sweden and in southeastern Missouri, U.S.A. and the giant Olympic Dam Cu-U-Au-Ag-KEE deposit in South Australia (Table 22-1). The breccia-hosted polymetallic Sue-Dianne deposit in the Northwest Territories is small and subeconomic, but it provides the best Canadian example of this deposit type (Fig. 22.1). All of these deposits are Proterozoic in age.

Large Phanerozoic deposits, mineralogically similar to the Kiruna deposits, occur in the circum-Pacific region (Chile, Mexico, China) and in Iran and Turkey. They are associated with intermediate to felsic volcanic and related plutonic rocks in orogenic settings and in relatively stable cratonic regions. Smaller occurrences of this type occur in the North American Cordillera, e.g. in the Tatoosh pluton of Mount Rainier, Washington, U.S.A., and in the Iron Mask batholith near Kamloops, British Columbia