348 THE VERMILION IRON-BEARING DISTRICT. 



greenstoiies to the slates is usually interrupted. A number of contacts 

 have been found, however, and in every instance where careful examination 

 was made at least a narrow belt of conglomerate derived from the green- 

 stone intervened between the greenstone and the slates. The localities at 

 which such conglomerates occur are described under the heading "Ogishke 

 conglomerate" (p. 317 et seq.). These conglomerates were found to be pres- 

 ent in practically every case in which careful search was made, and this fact 

 is the warrant for indicating on the maps in many places continuous belts of 

 conglomerate between the Knife Lake slates and the Ely greenstones. This 

 insertion has been made especially for the reason that thereby the structure 

 of the district can be made plainer. In almost every case, however, in 

 order to show this belt, it has been necessary to magnify many-fold the 

 true thickness of the conglomerate. In the NW. \ of sec. 17, T. 63 N., R. 9 

 W., contacts between the Knife Lake slates and the ellipsoidal Ely green- 

 stone can be found at many places. Here there is an eastward-plunging 

 trough of sediments infolded in the greenstones. Here and there a narrow 

 band of conglomerate occurs between the slates and the greenstone; else- 

 where, however, actual contacts have been found in which the slate lies 

 next to a zone of very schistose greenstone, which then grades down into 

 the normal greenstone. Evidently these deposits were formed in a fairly 

 protected area, as is indicated by the predominance of the slates over the 

 coarser graywackes and the scarcity of conglomerates along the border of 

 the greenstone. 



About 120 paces south of the Moose Lake end of the Moose Lake- 

 Flask Lake portage there occur numerous small outcrops of a porphyritic. 

 greenstone which has a more or less schistose green matrix, with numerous 

 white porphyritic crystals of feldspar evenly distributed through it. 

 Toward Moose Lake this porphyry becomes more and more fissile until 

 finally it passes into a schist. This schist is so beautifully and finely 

 laminated and fissile that it can almost be spoken of as a slate. Upon the 

 surfaces the flattened phenocrysts are shown. This schist belongs with the 

 Knife Lake slates. South of it lies a graywacke made up of disintegrated 

 material derived from the porphyry, with which it lies directly in contact. 

 There are no pebbles in this material which can be clearly recognized as 

 such. If any exist they merge into the matrix, and the two rocks, the 

 schistose porjDhyry and the grit derived from it, resemble each other so 



