Structural features and some metallogenic patterns in the southern part of the Superior Province, Canada

Abstract

In the southern part of the Superior Province of the Canadian Shield the Quetico belt of metasedimentary rocks extends northeasterly from Minnesota, across the Kapuskasing zone of crustal rifting, to southeast of James Bay. The belt forms part of a broader northeasterly-trending orogenic zone, and truncates the more westerly fold trends in the lavas and sedimentary rocks of eastern Ontario and western Quebec. It is suggested that the Quetico trend is the younger, and that the Quetico belt demarcates the geographic limits of the Kenoran orogen.In western Quebec and eastern Ontario three granite-cored massifs are bounded on their northern flanks by curved, regional faults and synclinal belts of metasedimentary rocks. The most important of these, the Pontiac Massif, is associated with a corresponding sediment-filled depression on the west.A broad region extending easterly and northeasterly from Lake Superior can be distinguished from contiguous areas on the basis of the abundance and extent of belts of iron-formation, many of these associated with acid volcanic rocks. It is proposed that these rocks were formed either in a restricted period of time or in a restricted volcanic-sedimentary environment.Massive, stratabound, pyritic base-metal sulfide ore deposits are most abundant in pre-Quetico rocks. They do not seem to be related to the processes associated with the deposition of abundant iron-formation.