A Rb–Sr whole rock investigation of two acid intrusive bodies in the Superior Province of the Canadian Shield have yielded isochrons corresponding to ages of 2.39 ± 0.08 b.y. and 1.73 ± 0.05 b.y. Additional K–Ar data on separated minerals from each of these intrusive bodies supports the Rb–Sr data. The existence of a dike-like intrusion of the 1.73 b.y. rock into the 2.39 b.y. rock is also inferred from the data.

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