REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1902 Vl 



which were of a dubious type and of uncertain affinity. The 

 other was entirely surrounded by syenite, plainly an igneous 

 intrusive, but showing considerable variation and also differ- 

 ing considerably from the usual syenite, so that it is a question 

 whether it is properly to be correlated with that. This syenite 

 appears to cut out the anorthosite on the north and west, at 

 least the contact between the two rocks is an irruptive one, 

 and apparently the syenite is the younger, though the evidence 

 is not so decisive as one could wish. If the relations were prop- 

 erly apprehended, the syenite is the younger, and the anortho- 

 site is of the nature of a large inclosure in the other rock. Be- 

 sides the evidence derived from the character of the exposed 

 contacts, the coarseness of grain of the anorthosite and its lack 

 of tendency to become gabbroic, harmonize with this view. 



Wherever the main anorthosite boundary was reached, the 

 rock was found to be gabbroic, fine grained and gneissoid, these 

 characters fading out with recession from the boundary. No 

 gradation between it and the syenite was noted, the boundary 

 between the two seeming everywhere sharp, but no contacts 

 were noted. 



The area of Grenville rocks lying south and southwest of 

 Follensby pond was found to have much greater extent than 

 had before been supposed, and to form much the largest area 

 of these rocks yet found in the heart of the region. Only its 

 north and west boundaries were mapped, but it was followed 

 for 4 miles from north to south, and, where left, was running 

 south with a breadth of at least 3 miles and possibly much 

 more. At least 10 square miles of it were included in the area 

 mapped, and it may be double that size or more. Compared 

 with most areas of these rocks too, there was singularly little 

 mixture with gneisses of doubtful or of igneous origin, the 

 rather frequent outcrops showing distinctive sediments only. 

 It is noteworthy that the area is not very remote from the con- 

 siderable belt of similar rocks which Prof. J. F. Kemp has 

 mapped as running east from Long Lake village, and which is 

 also of unusual size for the heart of the Woods, and that both 

 lie in what the writer has called the " lake belt," which he has 



