Abstract

Three different zircon size fractions, prepared from a single sample of Uivak II gneiss, yielded highly discordant lead–uranium isotopic ratios. The data define a discordia chord which intersects concordia at 3760 ± 150 Ma and about 2500 Ma. The upper intersection is interpreted as the time when the rocks were metamorphosed while the lower intersection records a major episodic lead loss event coincident with the youngest granitic activity in the area.

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