Rocks of the anorthosite-mangerite suite were intruded in many places in the southern part of the Grenville province of the Canadian Shield. These rocks, known as the Morin series in southern Quebec, are described from two contrasted areas, one in which there has been intense deformation during the emplacement of these rocks and in the other only mild deformation. Differences in the mineralogy and chemistry of these rocks in the two areas can be related to the degree of deformation.