GEOLOGY OF THE SCHROON LAKE QUADRANGLE 3I 



sists of alternating bands of partly white and partly rather gab- 

 broid Whiteface anorthosite. 



An interesting ledge outcrops in the small mapped area 1J/2 miles 

 a little west of north of Irishtown. The rock is extremely gneis- 

 soid, rnoderately gabbroid, Whiteface anorthosite containing many 

 lens-shaped labradorities or " augen " up to i^ inches long, and 

 in some portions red garnets. This anorthosite also has in it many 



Fig. I. Sketch of part of an exposure on top of Wilson mountain showing 

 small inclusions of IMarcy anorthosite in gneissoid granite. Note the 

 magmatic flow-structure foliation about the larger fragments. 



inclusions of Grenville hornblende-garnet gneiss in the form of 

 lenses, strips and layers from less than i foot long to i or 2 rods 

 long, these being arranged parallel to the foliation of the ledge. 

 It is thus certain that this anorthosite must have been in a truly 

 magmatic state when it caught up the fragments of Grenville. The 

 immediate relation of this ledge to the nearby syenite is obscured 

 by drift, but no doubt it is an inclusion. 



Along the western side of the Beech hill anorthosite, which is an 

 inclusion in the syenite-granite, there are, in the granite, some 

 small, irregular inclusions of Whiteface anorthosite with indefinite 

 boundaries, and with distinctly curving flow-structure in the granite 

 around them. 



In the narrow belt one-fourth of a mile long, already described 

 as extending across the southern brow of Cobble hill, many small 

 inclusions of the Whiteface rock occur in the granite. 



A number of inclusions of the Whiteface rock, each from i to 

 20 feet across, are finely shown in the granitic syenite on top of 

 the hill I mile east-southeast of Cobble hill. 



