THE LOWER HURONIAN. 341 



sediments are now metamorpliosed to mica- and ampliibole-schists. Occa- 

 sionally garnets have been produced as tlie result of contact action. The 

 metamorphosed rocks retain the sharp banding of the original sediments, 

 and there is also noticeable at many places a rapid alternation of bands 

 of different grain and composition. These bands are composed of feld- 

 spar and quartz, with epidote, amphibole, and mica. Variation in the 

 quantity and combination of these minerals causes a difference in their 

 appearance. A study of almost any of the exposures in the area south of 

 the Kawishiwi River in which these rocks occur as outlined on the maps 

 shows clearly the cause of the alteration. They are penetrated at numer- 

 ous places by dikes of granite which are offshoots from the great mass 

 of Giants Range granite which lies in contact with these schists on the 

 south. The granite dikes become more numerous as we go farther south 

 nearing this contact, and at the south end of the portage above referred to, 

 on the ridge just overlooking Clearwater Lake, the granite dikes are more 

 numerous and of larger size than at other places. Here, moreover, there is 

 an exceedingly good example of an eruptive breccia. The breccia consists 

 of dark-gray and black schist fragments derived from these metamorphosed 

 sediments, which are cemented by a matrix of the grayish and pink Griants 

 Range granite. Farther south, within the main mass of the granite, as on 

 the islands in Clearwater Lake and elsewhere, it attains its normal grain 

 and characters. In the dikes its characters are likely to vary as well as its 

 grain, depending upon the size of the dikes and the position in the dikes 

 from which the specimen is taken. Mountain-making movements may have 

 affected and unquestionably did affect these sediments to some extent. It 

 probably aided in making them schistose. What other effects it ma}^ have 

 had have been concealed, however, by the contact effects of the intrusive 

 granite. 



In the vicinity of Snowbank Lake, especially on the bare hills south- 

 west of it, in sees. 10 and 17, T. 63 N., R. 9 W., the Knife Lake slates are 

 well developed and are splendidly exposed over large areas. The slates 

 have been intruded by the Snowbank granite and from them have been 

 produced mica-schists, which predominate, with subordinate amphibole- 

 schists. The same kind of effect has been produced by the intrusion of the 

 Cacaquabic granite on the slates nearest it, although, since the slates 

 are not exposed very near the granite, the effect is not so marked. 



