230 N. L. BOWEN 



In the vicinity of Piedmont occasional dikelets are seen cutting 

 the anorthosite, which are found to consist principally of micro- 

 perthite with some quartz and an unusually large amount of 

 magnetite, a composition that suggests a syenitic source. Taken 

 all in all the evidence favors the possibility that we have in the 

 Morin area syenite and anorthosite related in the same manner as 

 in the Adirondacks, in part transitional into each other, but the 

 syenite of somewhat later consolidation. Even in the matter of the 

 occurrence of a certain aberrant type the two regions show a 

 further similarity. In the vicinity of Elizabethtown, New York, 

 there is a peculiar dark rock resembling a basic syenite, but con- 

 taining phenocrysts of the blue labradorite which is described by 

 Kemp as the Woolen Mill type. 1 This rock is duplicated in both 

 megascopic appearance and microscopic characters in exposures in 

 the streets of the village of St. Jerome, Quebec. It is apparently 

 intimately related to both syenite and anorthosite. 



Concerning the structural relations of syenite-granite and 

 anorthosite it is impossible to say anything definite, since syenite 

 that may be regarded as probably related to the anorthosite has 

 not been delimited. About twenty miles east of the anorthosite 

 mass, syenite-granite makes its appearance from beneath the flat- 

 lying gneiss of the surrounding country. Adams considers that 

 the syenite is much more widespread, the gneiss of the surrounding 

 area forming merely a relatively thin and little disturbed roof 

 over it. If the anorthosite is, as in the Adirondacks, a deep-seated 

 portion of the same igneous complex, then in order to bring the 

 anorthosite and the roof gneiss into lateral juxtaposition a con- 

 siderable movement would be necessary, and it is found that, after 

 passing westward over a twenty-mile stretch of little disturbance, 

 the gneiss is then, on approaching the anorthosite, thrown into 

 sharp folds. 2 Moreover, we find on passing within the border of 

 the anorthosite mass that the typical roof gneiss with its occasional 

 bands of limestone is absolutely lacking, a fact that suggests that 

 the roof gneiss was nowhere superposed directly upon the anortho- 



1 " Geology of the Elizabethtown and Port Henry Quadrangles," N. Y. Stale 

 Museum Bull. 138, 19 10, p. 35. 



2 Adams, op. tit., pp. 11 and 12. 



