PETROLOGY OF CORDIEIRITE-ANTHOPHYLLITE GNEISSES AND ASSOCIATED MAFIC AND PELITIC GNEISSES AT MANITOUWADGE, ONTARIO.

Abstract

An interbedded sequence of amphibole, cordierite-anthophyllite, and pelitic gneisses occurs at the uppermost level in a folded volcanic-sedimentary sequence which forms the Manitouwadge synclinorium. The mafic gneisses probably represent altered mafic lava flows. Microprobe analyses of coexisting amphiboles from these rocks reveal phase relations in an AFM projection similar to those reported by Robinson and Jaffee (1969). The cordierite-anthophylite gneisses have the assemblage quartz-cordierite-anthophyllite-ilmenite plus or minus garnet, biotite, and plagioclase (An//3//5//-//5//0). Staurolite and/or gahnite occur as conspicuous enclaves most frequently in cordierite.