RELATION OF SYENITE-GRANITE SERIES 435 



most unreasonable to suppose that the chilled border would in some places 

 grade first into the syenite or granite and then into the anorthosite. 

 Either one of these might be the case, but not both. 



Bowen suggests that the syenite-granite may have developed between 

 the chilled border and the Marcy anorthosite and then have been rein- 

 truded through the chilled border. But by what stretch of the imagina- 

 tion can we regard the syenite-granite series to have been so largely rein- 

 truded that not any of it has been discovered in its supposedly original 

 position? Also when we think of the tremendous volume of syenite- 

 granite immediately around the anorthosite, how can we possibly imagine 

 the reintrusion of so much magma through the chilled border facies, 

 leaving this latter as a definite fringe about and grading into the anor- 

 thosite for so many miles ? 



SYENITE-GRANITE BODIES OF THE LAKE PLACID AND AUSABLE QUAD- 

 BANGLES ARE NOT DIRECT DIFFERENTIATES OF ANORTHOSITE 



In discussing the distribution of anorthosite and syenite, Cushing^^ 

 says: "The continuity of the main mass (anorthosite) is interrupted by 

 two considerable inlying bodies of other rock (chiefly syenite), one in the 

 Lake Placid region and the other near Keene. . . . Both of these in- 

 liers are entirely surrounded by anorthosite and lie well within the mass." 

 These relationships were, no doubt, suggested by the highly generalized 

 State geologic map. He suggests that the anorthosite body, while cooling, 

 may have developed a syenite cover, and that the two so-called inliers just 

 mentioned may be remnants of that cover which have not been removed 

 by erosion. The field facts, as I interpret them, are fatal to this view. 



In the first place, the Lake Placid mass referred to is not an "inlier" 

 (or, I would say, "outlier") at all. It is a great body of syenite, with 

 locally developed granite facies, varying in vv^idth from 1 to 6 miles and 

 extending into the anorthosite area for 13 miles across the Lake Placid 

 quadrangle, and thence for an unknown distance into the Mount Marcy 

 quadrangle. I have definitely traced this mass right into the extensively 

 developed syenite-granite series of the Lake Placid and Saranac quad- 

 rangles, so that there can be no doubt about its being an offshoot from the 

 great syenite-granite body. The syenite mass north of Keene extends 

 eastward into the Ausable quadrangle, and there very likely connects with 

 the broad tongue of the syenite-granite series which reaches southward 

 for a number of miles into that quadrangle (see State map). Whether 

 the Keene syenite area actually connects with this broad tongue is not 



39 H. p. Gushing: Jour. Geol., vol. 25, 1917, p. 502. 



