II 

 SUDBURY, ONTARIO, TO DUNMORE, ALBERTA.* 



BY 



W. H. Collins and Charles Camsell. 



From Sudbury westward to Murray mine the main line 

 of the Canadian Pacific railway ascends among hills of 

 granite and highly folded Huronian greywacke, arkose, 

 quartzite and greenstone to the southern margin of the 

 great boat-shaped intrusive body with which the nickel 

 deposits of this district are associated. The southern rim 

 of the intrusive is crossed between Murray mine and Azilda, 

 the gossan and dark basic rocks of the outer edge passing 

 insensibly into flesh-coloured micropegmatite as the inner 

 edge just west of Azilda is approached. From Azilda 

 almost to Onaping the railway is within the elliptical area 

 enclosed by the rim of the nickel eruptive and for practi- 

 cally all of this distance it traverses a flat plain of stratified 

 clay formed in a part of old Lake Algonquin. The sand- 

 stone member of the Upper Huronian series which occupies 

 the basin of the nickel eruptive and underlies this lacus- 

 trine clay, outcrops in low, dome-shaped hills at Chelmsford 

 and Larchwood. The hilly rim of the nickel eruptive is 

 again crossed, from the acid to the basic edge, in the 

 neighbourhood of Onaping and Windy lake and a great 

 monotonous region of Laurentian granite-gneisses and 

 Keewatin schists is entered, which continues for the next 

 450 miles (725 km.). 



The granites and gneisses of this region are characterized 

 on the whole by an abundance of lime-soda feldspars and 

 range in composition from granite to granodiorite, less 

 frequently to syenite or diorite. But between Peninsula 

 and Middleton the railway crosses a plutonic mass of 

 nepheline and other alkali-syenites, 15 miles (24 km.) in 

 diameter. This is the only known area of alkaline rocks 

 in the region between Sudbury and Port Arthur. It is 

 described in greater detail in the guide book of Excursion 

 C I. 



As seen along the railway the alkali syenite mass appears 

 to possess a basic margin. Its eastern edge consists of dark 

 red augite syenite. This gives places more or less grada- 

 tionally to pale feldspathic syenites in the centre of the 

 area near Coldwell, and from Coldwell to Middleton the 



*For a more detailed description of this portion of the Excursion see Guide Book 

 No. 8, Part I. 



