178 THE VERMILION IRON-BEARING DISTRICT. 



Even where the bands of slaty material in the rocks are not more than 

 one-fourth of an inch across, the slaty cleavag'e is perfectly developed and 

 stops abruptly at the adjacent more brittle cherty material. Thus we have 

 in this phase of the iron formation numerous layers showing good slaty 

 cleavage alternating Avith others in which it is absent. The slaty cleavage 

 is in such position in reference to the plications as to show that it developed 

 normally to the pressure. The lack of parallelism of the cleavage upon 

 opposite sides of the folds beautifully illustrates the principle that on 

 anticlines the cleavage on opposite sides of folds diverges downward and on 

 synclines converges downward. These alternating slate and jasper bauds 

 are well shown in the so-called "Burnt Forties" adjacent to Vermilion Lake. 



While usually deformation has taken place without fracture, the jasper 

 is sometimes brecciated. We sometimes find very pretty "reibungs" or 

 friction breccia formed of the jasper fragments cemented together by vein 

 quartz. Not uncommonly such a brecciated zone occurs near the base of 

 the iron formation, 'between it and the lower -lying greenstones, and is thus 

 clearly the result of movement along the plane separating the two kinds of 

 rocks. In such instances, the jasper, being the more brittle of the two 

 ■ rocks, forms the angular to partly rounded fragments of tlie breccia, whereas 

 the greenstone, in some cases at least, is found to have been forced in 

 between the jasper fragments and to play the part of a matrix cementing 

 the breccia together (PI. VI, C). The plane of brecciation being more open, 

 has been especially favorable for the free movement of underground water. 

 Similar brecciated zones at the base of the jasper — that is, between it and 

 the greenstones — -due to movements along this plane, occur near the west 

 end of Emerald Lake, just north of the international boundary, on the 

 point that projects eastward from the south shore of this lake. Consequent, 

 upon this brecciation there has been infiltration of various substances, 

 especially of quartz and iron oxide subsequent to the formation of the 

 breccia, which also tends to cement the fragments together and likewise to 

 discolor the rock. 



On the east end of Lee Hill, on the south side of the old North Lee 

 mine, there is a brecciated zone in which the above-mentioned conditions 

 can be observed. It is further very noticeable here — and the same thing 

 may be seen at other places — that the fragments are frequently cemented 

 together by very pure hematite, and when there were favorable cavities of 

 sufficient size subordinate bodies of very high-grade ore were deposited. 



