Abstract

Uranium mineralization is hosted in a metasedimentary sequence intruded by felsic and mafic bodies in which the zircon U-Pb systems are 1,730 to 1,740 m.y. old. Felsic dikes characterized by exceptionally high uranium contents crystallized at essentially the same time (1,737 + or - 15 m.y.). Primary Rb-Sr systematics in these igneous rocks are profoundly disturbed. U-Pb discordia establish age of uranium mineralization as 1,550 + or - 15 m.y. Derivation of uranium protore in the host rocks prior to regional metamorphism and 1,550-m.y. uraninite formation was probably by ca 1,740-m.y. hydrothermal activity.--Modified journal abstract.

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