A. Wandke — Study of Cape XeddicJc Gabbro. 297 



line of body is oval there is a distinct flattening of the 

 southwestern margin along which the contact phenomena 

 are also less intense. Along the northeastern contact a 

 marine terrace, well exposed at low tide, shows in part 

 how the emplacement of the gabbro was effected. 



As has been mentioned, the qnartzite formation strikes 

 about 45 degrees NE. At a distance of two hundred feet 

 from the contact this strike remains undisturbed. At 

 about one-hundred and twenty-five feet from the contact 

 the strike of the sediments becomes slightly flexed. 

 Within the next twenty-five feet this flexing increases in 

 amount and passes into gentle folding the folds becoming 

 steeper the nearer one approaches the contact until at 

 seventy-five feet therefrom they pass into overturned 

 folds which in turn are broken by overthurst faults. 

 About fifty feet from the contact the sediments that else- 

 where in this region form an easily recognized lithologic 

 unit having a remarkable persistency of strike and dip 

 lose their identity and become a jumble of blocks of 

 quartzite cemented by gabbro. "Within five feet of the 

 contact the sedimentary nature of some of these blocks 

 is almost obliterated. The actual contact because of the 

 marked alteration of the sediments is established with 

 difficulty. 



To emplace this body a force would have been required 

 great enough to bodily thrust the enclosing rocks 

 asunder, at the same time folding them and producing a 

 shatter breccia. But such a lateral thrusting could not 

 alone account for the full width of the stock. The stock 

 is half a mile across whereas the total visible movement 

 in the contact zone about the intrusive accounts for but a 

 few feet of this width. In the contact zone the sediments 

 are brecciated and blocks of quartzite are frozen in the 

 gabbro. This would at once suggest that magmatic 

 stoping has been operative, but stoping hardly accounts 

 for the width of this intrusive for the expansion in 

 volume of the last 500 feet of stoped sediments would 

 have entirely filled the space now occupied by the gabbro. 

 It seems, therefore, that stoping may have played but a 

 very minor part in the emplacement. 



The emplacement of this body may be accounted for 

 if one considers that the intrusive moved upward in a 

 zone of tension. A rupture within this zone would par- 



