PLATE LXXX. 



THE FRASER LAKE PLATE OF THE MESABI IRON RANGE, 1899. U. S. GRANT. 



This area rivals that of the Snowbank Lake plate in interesting geological prob- 

 lems. On both much work has been bestowed, both in the field and in the labora- 

 tory. These problems are discussed in their order in volumes iv and v. 



The most indubitable proof of the origin of the granite of Kekequabic lake from 

 clastic Upper Keewatin strata can be seen about the southern shores of that lake. 

 This is the product of intense metamorphism of comparatively acid rock. As the 

 original rock passes to less and less acid character the resulting massive rock has a 

 different composition. It can hardly be styled granite because of the presence of 

 some of the minerals of gabbro, nor yet gabbro because of the presence of so many 

 granitic elements. In this transition interval are the rocks muscovadyte, with its 

 variations, " contact rocks," porphyrel, conglomeratic granite, mica schist and noryte, 

 some being due to variations in the original clastic and some to different degrees of 

 metamorphism. 



It has been assumed that the granitic metamorphism represented by this plate 

 was earlier than that due to the Cabotian disturbance of the Keweenawan, but that 

 is not proven. It may be found that this and the Snowbank Lake granite are of the 

 same date as the gabbro. 



The iron ore that is seen on the north shore of Fraser lake and on the south 

 side of Gabemichigama lake, pertain to the gabbro-greenstone zone of transition. 

 They are in the midst of more or less siliceous muscovadyte or quartzyte, and are 

 supposed to be derived from original jaspilyte lodes that existed in the Lower 

 Keewatin prior to the gabbro revolution. N, H. w, 



