Abstract

Three metavolcanic units in the Uchi–Confederation Lakes greenstone belt have been dated by the zircon U–Pb method. Ages obtained reveal a time interval of graphic separating the cycle I crystal tuff (2958.6 ± 1.7 Ma) from the cycle III rhyolite (graphic). A cycle II rhyolite about 2794 Ma old lies between the other two units. Uranium-rich xenocrystic cores occur in the cycle I zircons and are indirect evidence of preexisting sialic material.A metamorphosed granodiorite, intrusive into the cycle III rhyolite, is about the same age as the rhyolite. A post-metamorphic quartz monzonite pluton is dated at 2729.6 ± 1.3 Ma. A period of dynamothermal metamorphism in this portion of the Superior Province indirectly dated at graphic reflects the Kenoran orogeny.

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