UPPEK HUEONIAN. 



385 



with the iron and sihca of the adjacent rock might, where the elements were 

 present in proper proportion, very well produce the actinolite, griinerite, 

 and massive hornblende which in some places more or less completely fill 

 out these rounded areas. 



The following partial analyses of the iron ores of these Gunflint beds 

 are quoted from Winchell and Grant, and are of interest as showing the prac- 

 tical absence of titanium from them." In this respect they differ very 

 essentially from the titaniferous magnetite ores which form a part of the 

 Duluth gabbro of this vicinity. 



Analyses of iron ores of Gunflint heds. 



These iron-bearing rocks were observed by Chauveuet in his recon- 

 noissance through this district in 1884.'' They were also studied by 

 Bayley " and described by him in his articles upon the Duluth gabbro of 

 Minnesota. Chauvenet apparently considered these rocks as a part 

 of the gabbro. W. N. Merriam has also mapped these rocks as part 

 of the gabbro, and Bayley has also described them as a peculiar periph- 

 eral phase of the gabbro. H. V. Winchell, of the Minnesota survey, 

 first suggested that they were a phase of the Gunflint formation meta- 

 moiphosed by the gabbro.'' This is believed to be the correct expla-. 

 nation of the origin of these peculiar rocks. This explanation was 

 adopted by Spurr and also by Grant, who has described the rocks in 



a Analyses Nos. I, II, III, and IV, are from Geol. and Nat. Hist. Survey of Minnesota, Bull. 

 No. 6, 1891, p. 138. No. V is from Geology of the Mesabi Iron Range, by U. S. Grant: Engineers' 

 Year Book, University of Minnesota, 1898, pp. 49-62. Geol. and Nat. Hist. Survey of Minnesota, 

 Final Kept., Vol. IV, 1899, p. 480. 



6W. M. Chauvenet, U. S. Geol. Survey, MS. Notes. 



«The basic massive rocks of the Lake Superior region, by W. S. Bayley: Jour. Geol., Vol. I, 

 1893, pp. 433-716. 



('Geol. and Nat. Hist. Survey of Minnesota, Twentieth Ann. Kept., 1893, pp. 120-121, 134-136. 



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