n6 



Keewatin. — The series consists chiefly of basic to acid 

 volcanics, much decomposed, and generally schistose ; 

 amygdaloidal basalts, serpentine, diabase, quartz or felds- 

 par porphyry, felsite, iron-formation and rusty weathering 

 carbonates, and other rocks have been recognized. 



Keewatin. 



The Keewatin has a much greater distribution in the 

 Porcupine area than the other members of the pre- 

 Cambrian, and it is also of more importance economically, 

 since it contains the greater number of the gold-bearing 

 veins which have so far been discovered. 



As in other parts of Ontario, the series is highly 

 metamorphosed, and many rocks are so much altered as to 

 give little evidence of their original character. However, 

 much of the series can be seen to consist of basic and acid 

 volcanics such as basalts and porphyries, with intermediate 

 types, although these are often altered to schists. Where 

 schistose, the general strike over a considerable area is 

 found to vary from east and w r est to northeast and south- 

 west, while the dip is generally steep to the north. 



Basic Rocks. Among the more massive rocks are 

 greenstones (basalts, etc.), which frequently show a 

 striking ellipsoidal or pillow structure. Amygdules often 

 accompany this structure and occur most abundantly along 

 the rims of the ellipses. The centres of the ellipses are 

 often bleached to a light greenish or whitish color, whereas 

 the margins are considerably darker. This structure is 

 frequently seen in the northwest part of Whitney township. 

 It is very pronounced in the greenstone along the shores of 

 Night Hawk lake and on the islands in this lake. On the 

 main land, opposite Callinan's island in Night Hawk lake, 

 the ellipsoidal greenstone has been rendered quite schistose, 

 so that the structure appears as alternate light and dark 

 bands. Some of the greenstones have been brecciated and 

 resemble conglomerate. 



Serpentine occurs in parts of the area in large volume. 

 The range of hills immediately southeast of Porcupine lake 

 are largely composed of this rock, which is impregnated 

 with much carbonate. Occasional veinlets of fibrous asbestos 

 are seen. A section of a sample of serpentine rock from 



