Multiple dikes in Lower Kam Group, Yellowknife greenstone belt: Evidence for Archean sea-floor spreading?

Abstract

A mafic intrusive-extrusive complex at the base of the Kam Group in the Archean Yellowknife Supergroup at Yellowknife, Northwest Territories, Canada, grades from gabbros through a zone of multiple and sheeted dikes into massive and pillowed flows with thin beds of interflow sediments. Although rock types and primary structures resemble those in upper parts of Phanerozoic ophiolites, the Kam Group lacks an ultramafic base and is much thicker than typical ophiolites. Because similar mafic sections occur in certain atypical ophiolites and in plateau areas of modern ocean basins, however, the Kam Group is viewed as a remnant of Archean oceanic crust rather than as a product of intracontinental rift volcanism. The dikes are analogous to sheeted dikes of ophiolites and are suggestive of sea-floor spreading in an Archean marginal-basin setting.