Obedjiwan (Gouin Reservoir)

An approximately circular complex 7 km in diameter with a smaller, separate intrusion to the north, Obedjiwan consists of a core of nepheline syenite surrounded by aegirine syenite, which may be in the form of a ring dyke. The few outer contacts exposed are steep. A small plug of ijolite is probably only about 100 m in diameter and lies within the nepheline syenite. Nepheline syenite pegmatites with calcite cores are widespread. The aegirine syenite consists of perthite, aegirine and minor magnetite. A few boulders of biotite-calcite rocks on the flanks of the northern satellite intrusion may represent sheets in the intrusion. The nepheline syenite of this satellite reaches a grain size, in its uppermost part, of about 10 cm.