THE PRE-CAMBRIAN OF WESTERN PATRICIA 397 



muscovite are largely developed. This type of granite occurs on 

 the Wennasaga River from a point about ten miles above Slate 

 Lake to Hailstone Lake, and also on Pakwash and Little Shallow 

 lakes, where it has a syenitic phase with very little quartz. The 

 same intrusion may be represented by dikes on a small island near 

 the outlet of Lac Seul, which are composed of mica diorite. 



Granites and gneisses of the red type were observed to the south 

 of South Cove, Lac Seul, on the lower Wennasaga River, in the 

 Cat River basin from Big Portage Lake to Springpole Lake, and 

 on the lower Woman and Trout Lake rivers. 



The relations in age between these two types of granite were 

 not observable on the route followed by the writer. Both are 

 post-Keewatin. The gray type is later also than the upper schist 

 series, and both may be. If one is Laurentian and the other later, 

 say Algoman, the Algoman is the gray granite. 



There is, in addition, a coarsely porphyritic red granite intrusive 

 in the red granite-gneiss of the Birch Lake River. It was not seen 

 in contact with the schists, either upper or lower. This porphyritic 

 granite is distinguished from the others by the presence of acces- 

 sory titanite. 



We pass now to the area studied during the summer of 192 1 

 which lies along the Ontario-Manitoba boundary, a north and 

 south meridian line, and is on the average about seventy-five miles 

 (from sixty to one hundred) west of the field already described. 

 Here we find as the oldest constitutents of the complex two series 

 of rocks quite similar hthologically, and in their stratigraphic 

 relation to each other, to the two series of schists already 

 described. 



I. The lower is a predominantly volcanic series which includes^ 

 greenstone (massive diabase and ellipsoidal lavas), quartz-porphyry, 

 rhyohte, trachyte-felsite, green and gray schists due to alteration 

 of these, and in one place a bed of white quartzite, partly iron- 

 stained which occurs on the south side of the Winnipeg River a 

 Uttle west of the boundary, and has a total thickness of about thirty 

 feet. To these rocks the name "Rice Lake Series" was given by 

 Moore. 



^ E. S. Moore, Geol. Siirv. Can. Summary Report, 191 2, pp. 262 ff. 



