Garnet-cordierite gneisses near the Egersund-Ogna anorthositic intrusion, southwestern Norway

Graphite-bearing garnet-cordierite rocks from the Sjelset-Vikesá region, south Bogaland, Norway have been analysed by microprobe methods. The garnets belong to the pyropealmandine series and contain 28 mole% pyrope, while the cordierites contain about 71% of the Mg end-member. A regional temperature of about 720–750°C and a lithostatic pressure in the order of 6–7 kb have been inferred from the garnet and cordierite compositions. The petrographic observation suggests that such P---T conditions might reflect a retrograde metamorphic event. A tentative estimation of the fluid phase composition, based on the study of opaque minerals, is presented.