Abstract

The tectonic evolution of the Hurwitz Group, a widespread succession of predominantly metasedimentary rock up to 7 km thick in the Hearne province of the Canadian Shield, has not been fully evaluated due to a lack of absolute geochronologic data. The Hurwitz Group has been interpreted previously as either a passive-margin foredeep sequence associated with the 1.9-1.77 Ga Trans-Hudson orogen, or correlative with the Snowy Pass and 2.45 Ga Huronian Supergroups, located on the Wyoming and Superior cratons, respectively. U-Pb baddeleyite-zircon analyses from a gabbro sill yield a minimum age of 2094 +26/-17 Ma for the lower parts of the Hurwitz Group, which could be as old as ca. 2400 Ma, depending on the time of metamorphism. It is clear that the mafic magmatism and sedimentation documented in the lower Hurwitz Group are not linked temporally to the Trans-Hudson orogen, but rather are related to an earlier episode of crustal destabilization and extension, possibly the opening of the Manikewan Sea.

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