GEOLOGY OF THE SCHROON LAKE OUADRAiSTGLE 43 



north of the small gabbro stock. An inclusion of particular 

 interest is shown in figure 8. 



The granite porphyry is quite certainly a differentiation phase 

 of the granite, and it is only moderately developed within the quad- 

 rangle. One small area is represented on the map in the very 

 southeastern corner, and another on the southern brow of Ledge 

 hill, while the largest area (about 1 square mile) takes in the 

 vicinity of Pat pond. The granite porphyry differs from the 

 granite only in being coarser grained and usually more or less 

 porphyritic. 



Grenville or Hornblende Gneiss (Metagabbro?) and Syenite- 

 granite Mixed Rocks 



A number of small areas of mixed rocks of this sort are repre- 

 sented on the geologic map. The Grenville or hornblende gneiss 

 (metagabbro?) and granite are so intimately associated that any 

 attempt to separate them on the map would be unsatisfactory. The 

 old rocks are usually cut to pieces by, or form inclusions in, the 

 syenite-granite. 



In the small area just south of Calahan pond, typical granite 

 contains small to large well-defined inclusions of Grenville. In the 

 two garnet mines, the larger of which is located near the edge of 

 the map and the other just to the west, the rocks are highly granu- 

 lar red garnet in considerable masses closely associated with coarse 

 pyroxenic crystalline limestone. Contacts are sharp against the 

 granite in the smaller mine, but not in the larger one. A few rods 

 to the north and by the old road, there is a small, sharply defined 

 inclusion of limestone in the granite parallel to the foliation of the 

 latter. 



In the area covering about one-half of a square mile southwest 

 of Minerva there are many outcrops of both granite and Grenville, 

 the two often being closely associated in single outcrops. Evi- 

 dently the Grenville has here been badly cut to pieces by the 

 granite. 



The mixed rocks of the small area 2 miles north of Minerva are 

 described along with the associated iron ores in the last chapter of 

 this bulletin. 



At and near Lester dam there are extensive outcrops of pinkish, 

 very gneissoid granite containing much hornblende gneiss in the 

 form of flattened or lenslike inclusions more or less fused into the 

 mass. 



