The tertiary dike swarms of the Kangerdlugssuaq area, East Greenland

Abstract

Detailed field studies supplemented by petrographic and petrochemical data of dikes in the Kangerdlugssuaq area lead to the recognition of six distinct generations, which may be correlated with the major structural and magmatic events in this part of the North Atlantic Province. In order of decreasing age these swarms are: 1. A broad coastparallel dike swarm of high Fe and Ti tholeiitic basalts, identified as feeders for the plateau basalts of East Greenland and intruded prior to coastal flexuring. 2. A radial tholeiitic dike swarm with MORB affinities, related both in chemistry and chronology to the major gabbroic plutons (including Skaergard) and penecontemporaneous with the coastparallel flexure of East Greenland. 3. A coastparallel alkaline dike swarm, most intense some 20 km inland, composed of picritic to hawaiitic rock types and intruded subsequent to flexuring. 4. Peralkaline rhyolites found in the immediate neighbourhood of the nordmarkitic syenites and clearly related to the major period of salic plutonism. 5. A radial strongly alkaline swarm, including several types of alkaline olivine basalts and trachybasalts differentiating to oversaturated trachytes. 6. Simultaneous with the last, a coastparallel dike swarm composed of transitional basalts differentiating to rhyolitic rock types.