394 O. E. LE ROY — GEOLOGY OF KIGAUD MOUNTAIN, CANADA 



Rigaud is composed mainly of a normal hornblende S3^enite pierced 

 in the northwest by an area of porphyr}'', which differentiates from a 

 quartz syenite variety to a tj^pical quartz porphyry. 



The other hills, so far as known, consist of an alkali rich syenite, 

 associated with a basic rock of the same petrographical province, such 

 as theralite or essexite, both of which' are totally different from the 

 Rigaud rocks. 



In tlie township of Grenville a mass of hornblende S3''enite of pre- 

 Cambrian age cuts the Laurentian and is itself pierced by a quartz- 

 syenite porphyry, both rocks being closely identical with those of 

 Rigaud. From the proximity of the two masses it seems probable that 

 either the}^ are continuous under the Paleozoic or that they are genet- 

 ically connected. 



It concluding, it may therefore be stated that in all probability 

 Rigaud has no genetic connection with tlie rest of the series, but a deti- 

 nite conclusion is abstained from until such a time when our knowledge 

 concerning the other hills is so increased as to permit of the range being 

 studied as a whole. 



