GF.OIOGY OF THE LONG LAKE QUADRANGLE 481 



The series of exposures that decisively settle the question 

 occur along the Wawbeek road within the first 4 miles eastward 

 from Tupper Lake. In the neighborhood of the village itself the 

 rock is quite typical augite syenite, though with a tendency t:) 

 become basic locally, well shown in the road metal quarry near 

 Raquette pond, where the rock is very hornblendic and lacks 

 feldspar augen [pi. 18]. The syenite runs eastward for about a 

 mile, then for an equal distance there are no outcrops, after which 

 they are numerous on both sides of the road, the best and most 

 continuous being south of it, where exposures run with practical 

 continuit}?- for another mile. The rock is chiefly anorthosite, 

 somewhat gabbroic, but by no means the normal border gabbro, 



]f yti 11 II It n irii n A' 



4-/(1 U II M H H 11 ti II II 



II II II II II 11 It II ri 



H lilt n II II ti II n 



II II ri It II I! <i n II II 



n II II 11,11 II •( II II II 



n II II II It tt It ii II It 



11 It H II II II 11 " H M 



n II n II II It II H It 



r^ J- J_ -1- J_ ^ H H H II II II II 



H + + + + + 



anorthosite syenite dike syenite 



Fig. 1 Relationship of syenite and anorthosite, as shown in an exposure 2 miles 

 northeast of Tupper Lake village, and not far south of the Wawbeek road. Scale i inch = 

 3i feet 



this , of itself suggesting that part of the mass has been cut 

 away by the syenite. In addition it is everywhere cut through 

 and. through by dikes of the syenite, both large and small, and 

 in increasing number as the main syenite mass is neared. The 

 wider dikes show a rock identical in all respects with the syenite 

 about Tupper Lake, sometimes basic, at others not so, and there 

 can be no question that they represent direct offshoots from the 

 main intrusion, cutting into the anorthosite. From these larger 

 dikes, composed of normal syenite, slender branches may be 

 Seen running out into the anorthosite, and in these the rock is 

 at once recognized as identical with that found in the more remote 

 slender dikes, giving a demonstration of their origin, and cf 

 the fact that they differ from the ordinary rock because of their. 

 slenderness, and hence more rapid cooling. In figure i is given a 



