CRYSTALLINE INLIERS IN THE HURONIAN. 127 



protrusions of the older rocks from beneath or whether some of them may not 

 be portions of the Huronian itself which have undergone further metamor- 

 phism. Among these inliers the following may be mentioned : A large one 

 between Goulais bay and St. Mary's river; a long narrow one occupying the 

 shore of Lake Huron between Thessalon and Mississagui rivers; a small one 

 in the township of McGiveriu ; three on Lake Wahnapitse ; one at Paul's 

 lake on Sturgeon river ; one to the east and one to the north of Lake Tema- 

 gami ; one on Lake Temiscaming ; two on the main Montreal river, and 

 several on its upper branches. 



In the middle of that portion of the belt in which Sudbury is situated 

 there is, besides the inliers mentioned, a long tongue of gneiss and red 

 quartz-syenite, which begins beyond the northeast corner of the township of 

 Garson and runs southwestward into Denison, a distance of thirty miles, 

 and is joined to the main body of these rocks to the westward by dark gray, 

 rather fine-grained, imperfect quartz-syenite and gneiss, which may be seen 

 all around Wia-shai-gaming (or " Fairbank ") lake. 



The gneiss and the quartz-syenite of these isolated areas in the Sudbury dis- 

 trict replace or pass into each other in such a way that it would be very difficult 

 to represent them separately on a geological map. A singular feature about 

 them is that both kinds are in many places broken up into separate masses 

 like large and small bowlders, the interspaces being filled by a breccia with 

 a dioritic paste, of which the fragments consist of the country rock or of a 

 finer or preexisting breccia of the same composition. This takes place over 

 such considerable tracts as to suggest the idea that these rocks may be under- 

 lain at no great depth by diorite which was in a soft condition after the 

 gneiss and syenite had been consolidated. 



The narrowing of the Huronian belt, which happens in the Sudbury dis- 

 trict, is due to the extension into it, from the westward, of a large area con- 

 sisting mainly of red quartz-syenite. This rock is of a medium texture and 

 has a very uniform character over several thousand square miles, except 

 that in some parts it gives place to red syenite without quartz and in others 

 to ordinary gneiss. The relation of this great syenite area to the vast Lau- 

 rentian country to the northwest has not been carefully determined, but it 

 appears to merge into the prevailing gneiss in that direction and is certainly 

 connected directly with that terrane. 



At some places within the syeniti,c area, as for example about two miles 

 west of Cartier, a massive fine-grained rock, like some varieties of graywacke, 

 may be seen passing into thoroughly crystalline quartz-syenite. The fine- 

 grained imperfect gneiss and quartz-syenite around Fairbank lake may 

 represent one of the earlier stages of the coarser and more crystalline varie- 

 ties of these rocks. An ordinary looking variety of gneiss is being formed 

 out of a slaty kind of graywacke in the township of Hyman. 



