358 THE VERMILION IRON-BEARING DISTRICT. 



the gabbro and the Giants Range granite is conclusively shown by the 

 presence of a dike of gabbro which occurs in the Giants Range granite upon 

 the portage at the falls of the Kawishiwi, in sec. 19, T. 63 N., R. 9 W. This 

 dike was not directly connected with the gabbro, but is macroscopically the 

 same and is only about a quarter of a mile away from the contact line 

 between the gabbro and granite massives. Attention may be called to one 

 further fact indicative of the intrusion of the granite by the gabbro, and 

 that is that the Giants Range granite near its contact with the Duluth 

 gabbro appears a little more basic than elsewhere, and approaches the 

 gabbro somewhat in general appearance. Thus the granite is found to 

 contain some augite. There seems in many places to be a transition 

 between these two rocks, although ordinarily the contact is sharp. The 

 transition rock is in a few places broken into round masses and these are 

 cemented together by a schistose chloritic material. One might conceive 

 of such a transition phase being equally likely to result from the intrusion 

 of the gi-anite into the gabbro. However, the above-mentioned dike seems 

 to clinch the relationship existing between these two rocks. 



From the preceding statement of facts concerning the relation of 

 the Giants Range granite to the adjacent rocks, we are enabled to draw 

 the conclusion that the granite was intruded after the Lower Huronian 

 sediments were deposited and before the intrusion of the Duluth gabbro 

 of Keweenawan age. 



FOLDING. 



As has been already intimated, the granite shows very slight efiPects of 

 crushing or of the action of mountain-building forces, but that it has been 

 exposed to a certain amount of pressure is clearly shown. Small granite 

 dikes cut through the adjacent greenstone areas and lie parallel to the 

 schistosity of the greenstones. They were probably intruded subsequent 

 to the production of this schistosity, and hence followed along the planes of 

 easiest parting, which were the planes of fissihty in the rock. Subsequent 

 to their intrusion these granite dikes have, however, been squeezed, for we 

 find that occasionally they have been broken into pieces and these broken 

 portions have been separated, and, in fact, in some cases even the fragments 

 of the dikes have been rounded until they have acquired a more or less 



