Abstract

Volcanogenic massive sulphide deposits at Anyox in the Tracy Arm terrane of the Canadian Cordillera are associated with a sequence of tholeiitic basalts with minor intercalated basaltic andesite tuffs and siliceous sediments. Sm–Nd and Pb–Pb systematics indicate an Early to Middle Jurassic age. The tholeiites are characterized by normal mid-ocean-ridge basalt to weak island-arc tholeiite trace element signatures with slight enrichment in large-ion lithophile elements and depletion in high-field-strength elements, high 207Pb/204Pb, and εNd(170 Ma) values of +8.2 to +8.4. The mineralized sequence is conformably overlain by argillaceous sediments and minor limestones. These features, combined with the location of the strata and similarities with the Spider Peak Formation of the Methow terrane, indicate an origin in a narrowing marginal basin that once separated superterranes I and II.

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