104 AUSTEALASIAN ANTARCTIC EXPEDITION. 



prominent foliation, through types in which, with increasing proportion of granite, no 

 parallelism of structure can be preserved. The direction of the bands is parallel to the 

 schistosity of the granite gneiss, which may be schistose as well as massive. In places 

 (p. 602) the dark minerals appear to have been taken up or digested by the magma 

 and to have crystallised out again in large blades. 



Here, again, we find the interpretation of phenomena among gneisses coloured by 

 the conception that everything happened when the granite was molten. The gneissic 

 characteristics have been impressed after the consolidation of the granite by the influence 

 of stress. The processes which result in crystalline schists are entirely distinct from 

 those which result in normal igneous rocks. Solution, as we know it in igneous magmas 

 and liquids, is inapplicable to bodies which are to all intents and purposes solid. The 

 so-called " basic " minerals which are found exhibiting parallelism are metamorphic 

 minerals which have arisen in response to the impressed external conditions which 

 have caused the gneissic characters. The gradual transition, observed by Fenner, is 

 simply significant of metamorphic diffusion, and it is obvious in the field because 

 the two rocks in contact have strong difference in colour. In perfect accord with 

 the theory of metamorphic diffusion, he states (p. 604) that where there is the largest 

 amount of dark basic rock the adjacent granite contains the greatest quantity of 

 dark silicates, and where the inclusions are rare the granite is very light coloured 

 and nearly free from ferromagnesian minerals. From this observation he rightly 

 concludes that the dark minerals in the massive granite are derived from the basic 

 rock. The term " granite " is persistently used throughout the paper, but it is 

 questionable how far it is correct to do so, for the normal rock of the series seems to 

 be a granitoid gneiss. But Fenner is impressed with the conception that the granite 

 is intrusive into the rocks of basic composition with laminated structure after the 

 manner of lit-par-lit injection. He has tried to examine the process by which a 

 thinly fluid granitic magma could be injected between the layers of an original 

 sedimentary rock. In doing so he finds difficulty in understanding how these thin 

 walls of original rock could remain intact during injection and, at the same time, allow 

 transfusion of material. 



Like many other workers Fenner has placed considerable value on the evidence of 

 the so-called inclusions and the transfusion. As has been pointed out in other cases, 

 " inclusions " in metamorphic areas do not necessarily signify an earlier age than the 

 enclosing primary granite. It does signify an age earlier than the development of the 

 metamorphic characters, but not earlier than the granite magma. There is nothing 

 in the evidence presented to show that these dark hornblende bands and " inclusions " 

 are not the metamorphosed product of thin basic dykes which, in the first place, 

 intruded the granite, and which, in the subsequent metamorphism, have had their 

 boundaries partially destroyed by metamorphic diffusion, and which have been fractured 

 and broken so that fragments can now appear detached and isolated as if they were 

 inclusions caught up by an invading magma. New mineral formations have 



