A note on the Obedjiwan nepheline syenite, central Quebec

The Obedjiwan nepheline syenite forms two lenticular masses, one about 4 km by 2 km centred near 48°41"N, 74°56"W, and a smaller body 5 km to the northwest. Both bodies are coarse grained and weakly foliated, but show a strong lineation, and schlier-like areas of finer grain, interpreted as blastomylonitic. They have been substantially recrystallized, probably under amphibolite or granulite facies conditions. A pyroxene syenite outcropping around the periphery of the nepheline syenite forms part of a regional mafic gneiss complex hosting the nepheline syenite. The mechanical strength of the regional complex may be the reason why the nepheline syenite shows relatively little deformation, since migmatitic granite gneiss north of the complex is much more strongly deformed. These observations suggest that the Obedjiwan nepheline syenite is fairly typical of Proterozoic nepheline syenite bodies along the Grenville Front, and not anomalously undeformed and unmetamorphosed, as previously reported.