254 THE VERMILION IRON-BEARING DISTRICT. 



has been developed iu a number of cases a parallelism of the feldspar and 

 quartz and, especially, of the mica and secondary chlorite. The quartz 

 shows clearly the effects of the crushing in the very common undulatory 

 extinction, in the fractures that pierce the phenocrysts, and in the granula- 

 tion of the phenocrysts, which represents the final stage. This crushing 

 has, of course, more or less completely obliterated the textures and has 

 usually greatly altered the minerals. Fractures passing tlu-ough rocks have 

 been healed by infiltrated quartz, or by secondary feldspar in cases where 

 the fractures cross the feldspar phenocrysts. In such a case the secondary 

 feldspar corresponds in extinction Avith the adjacent feldspar bordering the 

 fracture, but is fresh and clear, and is readily distinguishable by these 

 characters from the altered original feldspar. 



RELATIONS TO ADJACENT FORMATIONS. 



The acid rocks described above are younger than the adjacent Ely 

 greenstones and Soudan formation. They occur in dikes in both of these 

 formations and include fragments of both. Detailed descriptions of the 

 occurrences of some of these rocks will be found under the heading "Inter- 

 esting localities " (p. 255). 



Relations to Loiver Huronian series. — The relations of the granite of 

 Vermilion Lake to the Lower Huronian sediments will be discussed in 

 detail later. It will suffice here to state that these sediments have been 

 derived partly from the acid rocks and hence are younger than they. The 

 detailed proof of their relations will be given in the chapter devoted to the 

 discussion of these sediments. 



Interrelation of granites of Vermilion Lake. — The acid intrusives, while 

 of the same general age with respect to the older and younger sedimentary 

 formations, show certain age relations among themselves which are inter- 

 esting. The fine granite seems to be rather more extensively developed, 

 on the whole, than the rhyolite-porphyries and the granite-porphyries. 

 This granite is cut at several points by dikes of fine-grained granite-por- 

 phyry containing small quartz phenocrysts — for instance, on the point 

 south of Mud Creek Bay, on Sttmtz Island, on the island just west of 

 Stuntz Island, and at a locality just north of the prominent jasper outcrop 

 on the east side of Stuntz Bay. This granite-porphyry is in its turn found 

 to be intruded by the granite-porphyry containing the large quartz eyes. 



