268 THE VEEMILION IRON-BEARING DISTRICT. 



RELATIONS TO ADJACENT FORMATIONS. 



The granite of Saganaga Lake is found in contact with and showing 

 clearly its relations to the Archean Ely greenstone and the Lower Huronian 

 sediments — the Ogishke conglomerate, and the Knife Lake slates. 



Relations to Ely greenstone. — In the southern portion of the area under- 

 lain by the granite of Saganaga Lake, on the soiith shores of West Gull and 

 Gull lakes, and along the contact between the granite and the Ely green- 

 stone to the east of these localities, the granite penetrates the Archean 

 greenstones in numerous dikes. Moreover, the intrusive nature of the 

 granite is further shown by the fact that in the contact zone the greenstone 

 is metamorphosed by the granite to an amphibolitic schist, whereas at some 

 distance away from the contact zone — that is, beyond the influence of the 

 granite — the greenstones show their normal characters. 



On the northern side of the granite area, on the north and east shores 

 of Cache Bay of Saganaga Lake (this is within Canadian territory), the 

 same relations are clearly shown on a great number of exposures around 

 the shores of the bay. Here, too, the metamorphism of the greenstones 

 diminishes as the distance from the main mass of granite increases. Further- 

 more, the granite contains inclusions of rock derived from this greenstone. 



On Red Rock, West Gull, and Gull lakes there are in places in the 

 granite irregular fragments of hornblendic rocks that are believed to have 

 been derived from the ancient greenstones tlu-ough which the granites were 

 intruded. This intrusive relationship of the granite and greenstone has 

 been recognized by all geologists who have studied this area, except H. V. 

 Winchell," who maintains that the granite is derived from the greenstones, 

 or Keewatin green schists, as he calls them. 



Relations to the Lower Huronian sediments. — No such general agreement 

 has been reached among the geologists who have studied the Vermilion 

 district and the adjacent district in Ontario as to the relationship which 

 exists between the granite of Saganaga Lake and the adjacent sedimentaries. 

 A. H. WinchelP has decided that the granite is younger, as a granite, than 

 the sedimentaries, and that it was derived from them by processes of 

 progressive metamorphism. Lawson" describes it as intrusive in the sedi- 



« Geological age of the Saganaga syenite, by H. V. Winchell: Am. Jour. Sci., 3d Series, Vol. XLI, 

 1891, p. 389. 



^ Winchell, A., Geol. and Nat. Hist. Survey of Minnesota, Sixteenth Ann. Eept., 1888, p. 211. 

 (^Lake Superior stratigraphy, by A. C. Lawson: Am. Geologist, Vol. VII, 1891, p. 324. 



