Nelson plutonic rocks in Slocan Mining Camp were emplaced at least 160 m.y. ago (base of the Upper Jurassic). K–Ar apparent ages for intrusions of lamprophyre and Valhalla plutonic rocks are indistinguishable from those for Nelson plutonic rocks. Younger apparent ages were obtained for altered samples and indicate at least one period of alteration less than 120 m.y. ago.

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