THE METAMORPHIC ROCKS OF ADELIE LAND.-STILL\VELL. Ill 



with biotite and hornblende. Banding of a similar nature is found at Cape Denison, 

 where thin threads of basic magma intruded the granodiorite and have partially main- 

 tained their integrity during the metamorphism. Such banding is an igneous structure 

 which the metamorphism has not effaced, and is analagous to a lit-par-lit injection on a 

 small scale. Both fluxion banding and foliation are insisted upon by Flett in the Lizard 

 serpentine, in the gabbros, in the Kennack gneisses, and in the granite gneiss. But 

 there does not seem to be any great difference between the two except a mineralogical 

 one. The fluxion banding (p. 22) is marked by olivine and pyroxene, and the foliation 

 by serpentine, and it is stated that they are parallel to one another and are so intimately 

 connected that they seem to be parts of one phenomenon and must be closely allied in 

 origin. We also notice that the figure referred to both on page 22 and page 68 as an 

 illustration of fluxion banding is titled " The foliation banding in the serpentine." When 

 we consider the Lizard serpentine to be a metamorphic rock belonging to the epi zone 

 of metamorphism, it is probable that the so-called fluxion banding and foliation are 

 part of one phenomenon. 



" Injection foliation " is the conception which Flett puts forward to account for 

 the remarkable foliation of the system of gabbros dykes that penetrate the serpentine. 

 He states (p. 94) that the foliation of the dykes is in nearly all cases parallel to the 

 margin of the dykes, whatever be its course ; that it is equally well marked in the 

 horizontal, vertical, and inclined dykes, and when one foliated dyke cuts another each 

 has its own direction of foliation ; that consequently the schistosity at once suggests 

 fluxion movement ; that where a dyke bends the schistosity bends with it, and if a dyke 

 forks, each branch is foliated parallel to its length. It is therefore supposed (p. 23) that 

 " the dyke rock was forced upwards in a plastic state under severe pressures, and the 

 foliation was produced as the injection went on, being really an injection foliation." 

 If this is so, the mineral constituents are arranged parallel to the direction of pressure 

 instead of at right angles to it. Further, if non-uniform pressure is an essential factor 

 in the production of gneissic structures, then it is not right to connect the foliation of 

 these Lizard dykes with their infilling with liquid magma. Not till the dyke matter 

 has become solid can the non-uniform pressure affect it, and we can only avoid the 

 difficulty by permitting the plastic magma to have the properties of both a liquid and 

 a solid. This seems to us unreasonable, and we therefore think that the super-induced 

 foliation must find some explanation independent of any movement along the dyke 

 channels. The heat of the primary magma may be a contributing factor, but its 

 supposition is unnecessary, as other sources of heat can be found. Rejecting, therefore, 

 the theory of injection foliation, we tender the following for consideration. 



We have explained that there is good reason to think that the Lizard serpentine 

 has been developed from a peridotite by metamorphic processes. The development of 

 serpentine by meteoric waters, if present, is only subsidiary. The serpentine has been 

 forced to develop during geological time under the physico-chemical conditions in the 

 depths of the earth crust that exist in Grubenmann's epi zone of metamorphism or 



