54 



There is a hiatus in the cliff section owing to a deep 

 depression having been carved out of the schists by the 

 Permo-Carboniferous glaciers, this trough being now filled 

 with glacial dehris. 



(d) Impregnation near the Syenite Contact. — Close to 

 the contact the country rock is again seen, and the most 

 intense metamorphic effects of the syenite are to be observed 

 near the old jetty. The syenite itself, as well as the country 

 rock, becomes very micaceous, and the increase in this silvery- 

 grey-looking mica is so great at times that it is hard to tell 

 where the actual contact is. Tongues of non-porphyritic 

 syenite are thrust into the schists, whose folia are curved and 

 contorted, while veins of quartz and veinlets of quartz and 

 mica are also sent out into the invaded rocks. In places the 

 schistosity is largely destroyed, and a very compact, somewhat 

 dull, light-grey rock is developed, streaked with what appear 

 to be tiny parallel veinlets of mica. The rock is really a kind 

 of hornfels. 



In regard to the inclusions in the syenite it is noted 

 that whereas the smaller masses of schist have been changed 

 in colour from black to grey, in the larger masses this alteration 

 has only been marginal. The change in colour, as will be 

 seen presently, indicates a change in composition due to 

 transfer of material, and apparently this can be effected 

 without any appreciable loss in the sharpness of the bound- 

 aries of the xenolith. 



Microscopically the altered rocks vary a good deal in 

 texture and in the relative abundance of the constituent 

 minerals, but they are all characteristically composed of a 

 fine-grained mosaic aggregate of quartz, albite, and .chlorite, 

 producing a tpyical hornfels structure, fine and even in grain 

 (pi. i., fig. 6). 



Veins of chlorite or of quartz and chlorite, with rarely 

 a little albite and an occasional little apatite prism, traverse 

 the hornfels, often with parallel arrangement. These have 

 sometimes forced open a space for themselves and appear as 

 true veins, or the quartz and chlorite may be found as medium- 

 sized grains poikilitically enclosing the other constituents of 

 the rock. 



Some of the rocks show more or less frequent flakes of 

 pale-brown biotite intergrown with or passing into chlorite. 



In addition to the minerals already mentioned all the 

 rocks are characterized by quite an unusual development of 

 rutile in very tiny crystals, generally simple, but rarely show- 

 ing geniculate twins. 



In some of the slides traversed by quartz-chlorite veinlets 

 there are strings of rutile running parallel to the veins; 



