Primitive nephelinitic volcanism associated with rifting and uplift in the Canadian Arctic

Abstract

Considerable interest has arisen recently in the nature of plate tectonic events in Arctic Canada and northwestern Greenland during Cretaceous to Recent times¹. Relatively little is known, however, concerning contemporaneous volcanism, and detailed studies have only been made of the basalts related to the Baffin Bay spreading centre^2,3, and the Kap Washington peralkaline volcanics associated with regional doming and rifting of northern Greenland during the late Cretaceous⁴. We show here that the Freemans Cove volcanic suite forms a major petrological province of Eocene saturated to undersaturated volcanism in the central Canadian Arctic. This occurrence of basalts, nephelinites and phonolites is an example of intraplate magmatism of the type associated with continental rifting. Emplacement of the rocks has been controlled by graben-like faults formed during the Boreal rifting and Eurekan deformation of the Arctic plate. Magmatism was initiated when extensional deformation was transformed by pre-existing resistant structures into a region of compression and uplift, causing partial melting of metasomatized mantle. Primary nephelinite magmas unusually rich in Ba, Sr, La form a major component of the magmatism.