Mineralogy and geochemistry of two Amîtsoq gneisses from the Godthåb region, West Greenland

Abstract

Amitsoq gneisses are of granodioritic composition, consisting largely of quartz, oligocIase, microcIine, and biotite, with accessory amounts of hornblende, epidote, sphene, apatite, zircon, and allanite. Two of these rocks and their constituent minerals have been analysed for Rb, Sr, Y, Zr, Nb, es, Ba, the Iantha· nides, Hf, Pb, Th, and U by spark source mass spectrometry. The trace element abundances and the lanthanide distribution patterns for these rocks are not significantly different from those in relatively young rocks of similar bulk composition.