A study of Precambrian sedimentary rocks belonging to Division three of the Yellowknife group has been made. Samples for this study were obtained from an area 2 miles north of the northeast arm of Russel Lake near the granite contact. The rocks are greywacke, arkose and phyllite that have suffered low grade regional metamorphism. Shear zones that parallel the strike of the sediments have provided channelways for mineralizing solutions so that these zones now constitute mineral deposits important for their gold content. The shear zones contain, in addition to quartz and sulphides, an intergrowth of grunerite and hornblende similar to that found in the iron-bearing district of Lake Superior. This amphibole intergrowth is particularly well developed in an assemblage of thinly banded sediments containing a narrow (about 4") iron formation. Although Almandite garnet is found to a small extent in the shear zones, it is the characteristic wall rock alteration of these zones. An attempt has been made to show that the elongated "quartz pebbles” which occur in the shear zones, are of hydrothermal origin. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate