Palaeomagnetism of marginal syenites and fractionated rocks of the Ilimaussaq intrusion, South Greenland

Abstract

hagen, December, 20th 1976. https://doi.org/10.37570/bgsd-1976-25-11 Five sites (31 samples) from marginal augite syenites (<1175±9 m.y. and >1168±21 m.y.) of the Ilimaussaq peralkaline intrusion, South Greenland, give a mean direction of magne,. tisation D=253° , I = 70° and palaeomagnetic pole at 268°E, 38°N (a0, = 11°). The remanence is held by titanomagnetite; coercivity allld magnetic stability increase towards the mairgin of the intrusion and are associated with higher deuteric alteration states. The highly-unden;,aturated syenites in the interior of the intrusion (1168±21 m.y., 1150±28 m.y.) carry a weak ood partially stable remooence held by pyrrhotite; six sites (30 samples) give a mean direction of magnetisation D = 324°, I = 74° with a palaeomagnetic pole at 239°E, 73°N (a95 = 23°). The pole positions from this study correlate with poles derived from older Keweenawan rocks of North America; they show that the Great Logan palaeomagnetic loop (1300-1100 m.y.) is slightly larger than previously defined.