RELATION OF SYENITE-GRANITE SERIES 431 



Another body of syenite, shown in part only in the southeastern por- 

 tion of the Lake Placid quadrangle, extends northeastward into the 

 Ausable quadrangle and possibly connects with the great tongue of the 

 syenite-granite series Adiich extends southward for some miles into the 

 anorthosite of that quadrangle, but this has not yet been proved. 



Kemp's Elizabethtown-Port Henry map shows the syenite to cut out 

 the whole border facies of the anorthosite in several places. About 2% 

 miles northeast of Mineville a tongue of syenite only one-fourth of a mile 

 wide extends almost a mile into and through the border phase. These 

 facts, together with the occurrence of the small mappable masses of border 

 anorthosite in the syenite 1 and 2 miles, respectively, from the main area, 

 make it seem reasonable to regard the whole body of syenite shown on 

 the map as a great intrusive salient which cuts out the anorthosite body 

 for miles. 



SYENITE-GRANITE AND ANORTHOSITE MIXED GNEISSES 



Areas of mixed rocks of this sort represent masses of Whiteface anor- 

 thosite which have been more or less shot through and cut to pieces by 

 syenite or granite. Locally the rocks exhibit their characteristic features, 

 but they are too intimately associated to be separately shown on the geo- 

 logic map. 



In the Lake Placid quadrangle two areas of such rocks, each about 2 

 miles long, lie far within the general anorthosite area southwest of Wil- 

 mington (see figure 1). Irruptive contacts of syenite against Whiteface 

 anorthosite are not uncommon. These contacts are usually not perfectly 

 sharp, as though slight fusion of the anorthosite by the intruding magma 

 took place along the immediate borders between the rocks. The intricate 

 relationship of these rocks is very evident. 



In the Schroon Lake quadrangle I have been obliged to map a very 

 irregular-shaped area of some 4 or 5 square miles of similar mixed rocks. 

 In this case the Whiteface anorthosite is badly cut to pieces- mostly by 

 granite, but also by some syenite. 



INCLUSIONS OF ANORTHOSITE IN THE SYENITE-GRANITE SERIES 



The inclusions of anorthosite in the syenite-granite series furnish very 

 strong evidence that the syenite-granite body is an intrusive distinctly 

 separate from and later than the anorthosite. Such evidence is scarcely, 

 if at all, touched on by Bowen, probably because few examples of such 

 inclusions were known to him, these being the ones within the Long Lake 

 quadrangle. 



XXXIII— Bull. Geol. Soc. Am., Vol. 29, 1917 



