Abstract

The Eocene volcanic suite of the Freemans Cove area of Bathurst Island, Canadian Arctic Archipelago, consists of dikes, sills, small plugs, and agglomeratic vents. Lavas are preserved only as clasts in the vents. The bulk of the magmatism consists of nephelinite or larnite-normative nephelinites and basanites. Subordinate members of the suite include olivine melilite nephelinites, phonolites, and tholeiitic and alkali basalts. The magmatism is bimodal and intermediate rocks are absent. Many of the nephelinites and basanites have the geochemical characteristics of primary magmas, and it is proposed that these members of the suite represent an integrated series of primary melts erupted in an essentially unmodified state from the upper mantle. Other members of the suite are generated by the combined effects of high- and low-pressure differentiation of the primary melts. The igneous rocks are confined to the grabenlike Southeast Bathurst Fault Zone and were emplaced during uplift and compression of the region by the Eurekan rifting episode. The magmatism has the petrological characteristics of intraplate continental magmatism of the type commonly associated with rifting and doming.

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