RESUME OF LITERATURE. 109 



various 'i kinds of rocks present in the area is carefully determined and 

 represented upon the map (PI. II), which accompanies the article. With 

 the exception of the Keweenawan gabbro and certain diabase dikes, whose 

 age is undetermined, all the rocks described are included in the Keewatin. 

 The points of chief interest in the paper are of a petrographic character, 

 and consist in a description of some anomalous green schists, of a 

 hornblende-porphyrite, and of an augite soda-granite. Evidence is also 

 presented to show that this is a true igneous granite, and is not due to 

 crystallization of sediments in situ, as had been previously maintained in 

 papers on the region by other writers. 



1894. 



Grant, U. S. Preliminary report of field work during 1893 in northeastern 

 Minnesota: Twentj^-second Ann. Rept. Geol. and Nat. Hist. Survey Minn., for 1893, 

 1894, pp. 67-78. 



That part of the region studied by Mr. Grant, which is included in 

 the Vermilion district as described in this paper, lies in the Gunflint Lake 

 area, north of T. 63 N., and between Rs. 3 and 7 W. In Ts. 65 and 66 

 N., Rs. 4, 5, and 6 W., are Keewatin rocks, including the usual types — 

 volcanic tufiF, greenstone-schists, greenstone, and the Ogishke conglomerate. 

 The Saganaga granite is intrusive in the Keewatin, the rocks of which it 

 metamorphoses. The author feels himself justified in stating: 



(1) That the rocks called Vermilion in the region of the writer's field work are 

 not necessarily lower in the geological scale than the Keewatin, but that they occur 

 at various horizons in the Keewatin; (2) that they are only a more crystalline 

 condition of these same Keewatin rocks; and (3) that they probably owe their more 

 crystalline nature largelj' to their close proximity to areas of intrusive granite [p. 71]. 



The Animikie iron-bearing rocks of Akeley Lake lie upon the 

 Keewatin greenstone to the aorth, and on the south are overlain by the 

 Great gabbro mass. The belt has a width of from 300 to 1,300 feet and 

 a dip varying from 20° to almost vertical, but averaging 45° to 50°. 

 Where widest it has an average dip of 30°, which would make a maximum 

 thickness of 650 feet. The iron ore is a nontitaniferous magnetite. 



The Animikie rocks are little disturbed, except locally, having an 

 average dip of 8° or 10° a little east of south. The Animikie beds 

 are interleaved with diabase sills. These give parallel east-west ridges. 



