78 THE VERMILION IRON-BEARING DISTRICT. 



The problems to be solved in each region are briefly discussed. Here 

 reference will be made only to discussions of rocks occurring in the district 

 described in the j)resent paper. 



It is maintained that the series of rocks first called Animikie by Hunt 

 belongs below the Keweenawan rocks. These rocks are presumed to con- 

 tinue with interruptions from Thunder Bay along the boundary to Gunflint 

 Lake, and thence southwest to Pokegaraa Falls on the Mississippi. 

 Throughout a considerable part of its extent the Animikie series of rocks 

 is bordered on the north by a belt of granite and gneiss, forming the Giants 

 range, to the north of which again come the strongly folded schists of the 

 Vermilion district proper. The main question to be determined here is 

 what the relations of the Animikie to the schists may be. The hypothesis 

 is advanced that they were probably originally connected over the inter- 

 vening granite range, and are thus really a unit, which as the result of 

 erosion has been separated. 



Most of the rocks occurring in the region are sedimentaiies that have 

 been indurated by metasomatic action. With- these are associated erup- 

 tives, some of which have been so modified as to become schists. The 

 cherty and jaspery rocks are supposed to be some sort of original chemical 

 sediment, certainly not, however, the result of metamorDhism of ordinary 

 sedimentary material. 



1886. 



Irving, R. D. Origin of the ferruginous schists and iron ores of the Lake 

 Superior region: Am. Jour. Sci., 3d ser., Vol. XXXII, 1886, pp. 255-272. 



In this paper Irving discusses the origin of the ferruginous schists and 

 iron ores of the Lake Superior region. An examination of the Animikie, 

 Penokee, Marquette, Menominee, and Vermilion districts reveals the fact 

 that in all of them is found abundant carbonate of iron, which oftentimes 

 grades into the other forms of the iron-bearing formation. The silica 

 of the jasper, actinolite, magnetite-schists, and other forms of the 

 iron belt never show any evidence of fragmental origin, so easily 

 discovered in the case of the ordinary quartzites and graywackes, and 

 is presumed to be of chemical origin. Associated with the iron-bearing 

 beds is often a considerable quantity of carbonaceous or graphitic schists. 

 It is concluded, (1) that the original form of the iron-bearing beds of the 

 Lake Superior region was that of a series of thinly bedded carbonates, 



