Data on the origin of the Kipawa syenite complex, northwestern Quebec

The Kipawa Syenite Complex forms a persistent, thin, folded layer within tectonized biotite-magnetite granite gneiss structurally overlain and underlain by metasedimentary rocks which in turn rest upon Archean plutonic rocks. Kataphorite+biotite (±aegirine) syenite comprises about 5% of the complex. The rest consists of distinctive granoblastic textured quartz syenite and granite characterized by large porphyroblasts and pods of hastingsite. Amphibole and biotite commonly show replacement by magnetite with formation of red oxidation spots. Observations suggest formation of the Kipawa Syenite Complex during amphibolite grade metamorphism by metasomatic fluids derived from a peralkaline igneous complex whose relics appear as lenses of nepheline syenite and as allochthonous blocks of igneous-textured aegirine melasyenite. This process occurred during a late stage of the assembly of the Superior and Grenville provinces (ca. 995 Ma), more than 100 Ma after emplacement of the host gneisses, and 40 Ma after emplacement of the alkaline complex.