Abstract

Felsic intrusions spatially and temporally associated with Archean Au deposits in the Superior Province of the Canadian Shield are magnetic, due to high magnetite content, in comparison to felsic igneous rocks in most of the Archean terrain. Examples are found in Au camps of Hemlo, Red Lake, Harker-Holloway, Mishibishu Lake, Wawa-Missanabie, Geraldton, Matachewan, and Bousquet-East Cadillac. These Archean intrusions are comparable with Phanerozoic magnetite-series plutons accompanying metallic mineralization and magnetite-rich intrusions hosting Au-rich porphyry deposits. The evidence shows a distinct tectonic setting for the gold mineralization involving the generation of the particular magmas. The association of the two indicates either the derivation of the ore constituents from the intrusions or the emplacement of the magmas along dilation zones which also provided fluid flow from depth. The identification of magnetite-rich felsic intrusions may aid in targeting favorable exploration areas for Archean Au deposits.

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