394 



EECENT wore: OF THE GEOLOGICAL SrEYEY 



enveloped in crushed or reconstructed gneiss. In most cases the 

 northern portion of the dyke has been moved further towards the 

 ■west than the southern portion. 



Fig. 3. — Ground-plan, showing Deflection and Disruption of DyTces 

 by vertical TJirust-planes. 



T. Thrust-plane. 



D. Dyke, becoming attenuated and deflected and increasingly schistose as it 

 approaches the plane, and being reduced to a " crush-rock " in immediate vicinity 

 of the thrust. Displacement about ^ mile. 



Dotted lines indicate the strike of the gneiss, the planes being deflected as 

 they approach the thrust. 



The arrow shows direction of movement. 



The parallel lines indicate the newer schistosity produced in the gneiss within 

 the influence of the thrust. 



When the hornblende- schist is extremely fine-grained there is a 

 considerable development of black mica along the divisional planes, 

 the direction of the foliation being more or less parallel with 

 that of the thrust-planes; but variations commonly occur as the 

 folia curve round the patches of diorite or granular igneous rock. 

 When the orientation of the minerals in the hornblende-schist is 

 examined, it is found to point towards the west; and when this 

 fact is viewed in connexion with the deflection of the dykes, it is 

 clear that, with one or two exceptions, there must have been a 

 powerful movement towards the west, on the iiorth side of these 

 thrust-planes. 



Similar schistosity is produced by the third system of disruption- 

 lines, running jS'.E. and S.W., the direction of the foliation in this 

 case also being determined by the trend of the lines of shearing. 



