176 THE ROYAL SOCIETY OF CANADA 



Unconformity 



Granodiorite Jurassic ? 



Igneous Unconformity 

 Serpentine (altered basic intrusive) )^ Mesozoic ? 



Phoenix Group — (Porphyrites, tufifs, etc.) j 

 Attwood Series (Argillites, limestones, quartz, 



• jasperoids) Palaeozoic 



The description of the granodiorite, given in the Summary Report, 

 may be quoted : 



"At various points throughout the whole district, bosses, irregular 

 masses and dykes of a light-grey granitoid rock make their appearance. 

 It is a quartz-bearing biotite-hornblende rock, in places apparently 

 granitic, in others rather dioritic. It is probable that it will prove to 

 be, generally, a granodiorite. 



It sends out numerous dykes throughout the country, especially 

 in the southern portion of the district. These have usually a porphy- 

 ritic structure with a microgranitic groundmass " 



"The granodiorite is evidently intiusive cutting all the rocks^ 

 above mentioned. The mechanism of its intrusion is extremely in- 

 teresting for it unquestionably forced its way up th;-ough the overlying 

 rocks by digesting them and rifting off fragments. This is proved by 

 the contacts, both along the sides and roofs of the masses. These 

 are, except in the case of the dykes, rarely sharply defined, but are 

 irregular and suture-like. The intrusive holds inclusions of the sur- 

 rounding rocks, and the surrounding rocks are often filled with granitf: 

 material. 



The composition of the intrusive seems to be affected by the di- 

 gested material of the rock into which it has forced itself. It is also 

 shown by the way in which the granodiorite is exposed in small, more 

 or less circular but irregularly bounded masses in different parts of the 

 district such as in Wellington Camp and on Hardy Mountain. In 

 many cases no definite boundary can be assigned to the granitic mass. 

 From the way in which the rock makes its appearance in all parts of 

 the district, it is evident that the whole of it, at no great depth, is 

 underlain by this rock. This rock has a strong resemblance to the 

 Nelson granite of the Kootenay district both in composition and in 

 its relationship to the surrounding rocks. The Nelson granite which 

 has been carefully studied is a sort of granite representative of the 

 Monzonite group of rocks, intermediate between the alkali and lime- 

 alkali series of rocks and about on the boundary line between granite 

 and diorite." 



'AH the rocks given below it in the table of formations. 



