On the Norian or "Upper Zaurentian" Formation. 283 



In carefully examining the anorthosite rocks of the 

 Morin area we usually, if not invariably, observe in con- 



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Fig. 2. 



nection with the striped and irregularly banded structure 

 a peculiar fracturing or granulation in the constituents of 

 the rock. This structure is frequently very well exhibited 

 on large weathered surfaces. The accompanying sketch 

 (Fig 2) of an exposure near the village of St. Marguerite 

 shows this phenomenon. The banding is still distinct, but 



in nearly every part 

 of the area the rock 

 itself, even where no 

 striping is visible, 

 presents this peculi- 

 ar brecciated struc- 

 ture. Fragments of 

 plagioclase and ot 

 her constituents lie 

 in a kind of ground 

 mass, which consists 

 of smaller grains. 

 The apparently por- 

 phyritic elements 

 are only in a few cases idiomosphic plagioclases, but are, on 

 the contrary, almost invariably allotriomorphic fragments 



