i?. A. Daly — Secondary Origin of Certain Granites. 203 



C. The Sudbury Intrusive Sheet. 



A still more remarkable parallel to the conditions of the 

 Moyie sill has been rather fully described by Barlow and 

 Coleman, following the earlier work of Walker in their respec- 

 tive memoirs on the geology of the Sudbury District, Ontario. 

 In the scale of the various related phenomena, in the wonder- 

 fully systematic arrangement of the different rock-formations, 

 and in the occurrence of valuable ore-bodies directly and geneti- 



North 



South 



Fig. 5. Diagrammatic map of part of the Northern Nickel Kange, Sud- 

 bury District, Ontario; after Coleman. 



1. Granitoid gneiss, greenstones and graywackes. 2. Norite. 8. Inter- 

 mediate rock, transitional between norite and micropegmatite. 4. Micro- 

 pegmatite. 5. Slates, sandstones and volcanic tuffs. (The position of the 

 sulphide ores shown by heavy black line.) Conventional sign for strike and 

 dip. Scale : one inch = two miles. 



cally associated with the intrusive, the Sudbury District exam- 

 ple stands unique in petrographical records. 



The latest reports of Barlow and Coleman agree in the con- 

 clusion that the famous nickel-bearing eruptive has the form 

 of an enormous intrusive sill of a composition exactly analo- 

 gous to that of the Moyie sill excepting as regards the develop- 

 ment of the valuable sulphides. It is "a vast sheet of erup- 

 tive rock having a basin shape ; a sheet nearly 40 miles long 



