Kaersutite-Bearing Gabbroic Inclusions and the Late Dike Swarm of Kangerdlugssuaq, East Greenland

C. Kent Brooks and R. G. Platt
Institute of Petrology, University of Copenhagen
Grant Institute of Geology, University of Edinburgh1
1Present address: Dept. of Geology, Lakehead University, Thunder Bay, Ontario, Canada.

Summary: The Kangerdlugssuaq late dike swarm, which strikes at a high angle to the well-known East Greenland coastal swarm, is described and chemical analyses presented. The basic members are characterized by a high potassium content. A variety of kaersutite-bearing gabbroic inclusions in one member of this swarm is described in detail and microprobe analyses of clinopyroxenes, amphi-boles, plagioclases, sheet silicates, and spinel minerals are presented. On the basis of this evidence it is deduced that these inclusions derive from a cumulate sequence formed at depths of between 5 and 10 km beneath the Lower Tertiary land surface. It is likely that fractionation of such assemblages causes a transition, at relatively low pressure, from undersaturated to oversaturated compositions, but the products appear to be quantitatively minor.

Mineralogical Magazine; September 1975 v. 40; no. 311; p. 259-283; DOI: 10.1180/minmag.1975.040.311.07
© 1975, The Mineralogical Society
Mineralogical Society (www.minersoc.org)