AECHEAN GRANITES. 255 



Such an occurrence was observed in the Burnt Forties, for example. Thus 

 the succession, beginning with the oldest of the intrusives, is: Fine- to 

 medium-grained granite, fine-grained granite-porphyry with small eyes, 

 and coarse granite-porphyry with large quartz eyes. The relation of the 

 rhyolite-porphyry to the other acid eruptives is not definitely known, as no 

 occurrence has been found in which the relations lietween them are shown. 



INTERESTING LOCALITIES. 



Localities sliotving relation hetiveen granite of Vermilion Lake and the Ely 

 greenstone. — The relations between the acid intrusives and the Ely green- 

 stone are clearly shown at many places in the Tower area of the Vermilion 

 disti'ict. In the following paragraphs some of the most accessible of these 

 places will be mentioned. 



On the north shore of Mud Creek Bay, in sec. 1, T. 62 N., R. 16 W., 

 immediately north of the westernmost island in this bay, there is a broad 

 dike of nearly white medium-grained porphyry which trends east and west, 

 and can be distinctly seen from the water. This dike cuts directly across 

 the Ely greenstone, showing sharp contacts with it in many places. 



Just northeast of this place, on the section line between sec. 1, T. 62 N., 

 R. 15 W., and sec. 6, T. 62 N., R. 14 W., are dikes of granite cutting the green- 

 stone and the iron formation infolded in the greenstone. In fact, one can 

 hardly go a quarter of a mile in any direction over these nearly bare hills 

 without finding one or more of these acid dikes. The greenstone is in many 

 places schistose, and the dikes are also frequently found to be more or less 

 schistose along their margins, the schistosity striking a little north of west. 

 The presence of this schistosity is clear proof that the area has been folded 

 subsequent to the period of the intrusion of these igneous rocks. 



About the center of sec. 6, T. 62 N., R. 14 W., there is a large boss 

 of porphyritic granite, which is completely surrounded by more or less 

 schistose greenstone. Numerous dikes of granite, ranging from a few 

 inches up to 15 feet in width, and perfectly massive, evidently oftshoots 

 from this central boss, j^enetrate the greenstones. Frequently they follow 

 the schistosity, but in some cases they cut across the schistosit}-, and in 

 places they include fragments of the schist. Since the position of these 

 intrusives has evidently been influenced by the preexisting schistosity, they 

 were evidently intruded somewhat after those that have already been 



