ELY GREENSTONE. 169 



are dotted with abundant amygdules. In some instances amygdules are 

 scattered over large areas. In other instances they are collected chiefly 

 along certain lines which run about northeast. The individual lava flows 

 could not be distinguished. The amygxlules are now oval, with the long 

 axes of the ovals parallel with the schistosity of the rocks, which trends 

 N. 60° E. The amygdules range from very small ones to others which 

 are 3 inches long and three-fourths of an inch across the shortest diameter. 

 The accompanying illustration, PI. V, A, is a reproduction of the polished 

 surface of one of these metamorphosed amygdaloidal basalts. The rock 

 is now an amphibole-schist, and but for the presence of the amygdules 

 and its associations in the field it would not be recognized as a basic lava. 

 These greenstones are cut by dikes of granite as well as by narrow dikes 

 of basic rock. 



The ellipsoidally parted greenstones are well exposed in the west half 

 of sec. 17, east half of sec. 18, northeast quarter of sec. 19, and north- 

 west quarter of sec. 20, T. 63 N., R. 9 W. The ellipsoidal parting and 

 amygdaloidal characters of these rocks show clearly their identity with 

 the Ely greenstone in other parts of the district. The ellipsoids vary in 

 size considerably, and the matrix between them varies from one-half inch 

 to 2 inches in thickness. This matrix has been silicified to a consider- 

 able extent, and in places appears very much like a black chert. The 

 rocks have been extensively metamorphosed. This metamorphism is prob- 

 ably due largely to the effects of the Keweenawan gabbro, which at 

 jjresent is separated from the greenstone by the width of the Kawishiwi 

 River. Formerly, however, the gabbro unquestionably overlaid the green- 

 stone to the noi'th of the river. The greenstone is cut by a number of 

 dikes of basic rocks varying in width from a few inches to 30 feet. ^ The 

 dikes are dolerite and camptonite (?). 



METAMORPHISM OF THE GRBElSrSTONES. 



The greenstones of the Vermilion district have been extremely 

 metamorphosed by the intrusion of younger rocks, as well as — perhaps 

 chiefly — by the intense folding to which they have been subjected. The 

 oldest rocks, the Ely greenstones, have naturally been most metamor- 

 phosed, since they have been subjected not only to all of the folding 

 which affected the younger rocks, but to previous metamorphic action. 



