332 THE VERMILION IRON-BEARING DISTRICT. 



first formed, and as the conditions changed they graded into the rocks 

 forming the iron formation, which in their turn, as the conditions again 

 changed, graded again upward into normal slates. This was repeated at 

 least three times. On good exposures the belts of iron formation proper 

 are made up jJredominantly of jasper, iron oxide, and chert, but here and 

 there slate bands are present, and on the sides of such a belt the slate 

 gradually increases in quantity, jasper and ore gradually diminishing, iintil 

 we pass into a belt of finely laminated slate showing on the weathered 

 surfaces alternating pink, white, and greenish bands, with which there is 

 practically no jasper. 



The carbonate-bearing rocks occur at various places on Birch Lake. 

 They were always found along the contact between the greenstones and 

 the slates, and were a sure guide to the close proximity of the greenstones. 

 No jasper was found with these rocks. Essentially the same conditions 

 prevail on the north side of Carp Lake. At a number of places here the 

 belt of ferruginous carbonate-bearing slate was found between the green- 

 stones and the slates. At one place a series of bands of chert and jasper 

 was observed. These occur at the west end of the north arm of Carp 

 Lake, on the little point just opposite an exposure of the Ely greenstone. 

 They appear very similar to the slates and jasper that occur in the series 

 at This Mans Lake, northeast of this place. The greenstone shows its 

 tyjDical ellipsoidal characters and is separated from the jasper by_ an interval 

 of 2 feet. This occurrence corresponds very closely to that on the north 

 flank of the small greenstone anticline south of Knife Lake, in sees. 29 aiid 

 30, T. 65 N., R. 6 W. 



One can readily see how, in the course of the deposition of slates of 

 such great thicknesses as those that make up the Knife Lake slates of the 

 Lower Hurouian in the Vermilion district, there could occui" at different times 

 conditions favorable for the deposition of rocks from which might be derived 

 materials similar to the iron-bearing formation. We would thus expect to 

 find here and there throughout these slates rocks essentially similar to those 

 of the iron-bearing' formation. In this way we may account for the occur- 

 rence in the slates west of Ely, near the east quarter post of sec. 4, T. 62 N., 

 R. 13 W., of a series of alternating chert and cherty-slate layers bearing- 

 some iron. The less cherty layers contain a considerable quantity of iron, 

 • and weatlier with fairly brilliant red color. In this way, by the alternation 



