THE METAMORPHIC ROCKS OF ADELIE LAND. STILLWELL. 195 



leptynite (granulite). Such crystalline continuity is, therefore, quite independent of 

 the nature of the rocks, and is most likely an impressed metamorphic character. In 

 specimens showing a junction from the Cape Gray Promontory there is a gradual 

 microscopic transition from one rock to the other. 



In describing the garnetiferous leptynite as a pressure altered form of charnockite 

 (p. 142), Holland assumes that the set of metamorphic conditions which produced the 

 granulated selvages has also produced the garnet. He argues that the temperature 

 of crushing must be high. It can be pointed out that such is unnecessary as the 

 acquisition of mechanical structures may be subsequent to the development of the 

 garnet. 



The typical augite norite from St. Thomas Mount (p. 156) is very similar to the 

 plagioclase pyroxene gneiss at the Madigan Nunatak minus the mechanical structures, 

 but the hornblende plagioclase pyroxene gneiss from Aurora Peak seems identical with 

 the more common form of hornblende augite norite. If this comparison is correct we 

 would expect that the hornblende is derived at the expense of the pyroxene, but I have 

 not noticed this to be stated in references to the norites. Amphibolisation of pyroxene 

 in the pyroxenites, an ultrablastic form of the charnockites, is described (p. 169), and 

 it is noted (p. 170) that, whenever hornblende becomes a prominent constituent of the 

 pyroxenites, the norites have also a conspicuous amount of hornblende. This amphiboli- 

 sation is, therefore, a character which has probably developed by the impress of certain 

 external conditions which have affected both the norite and pyroxenite together, i.e., 

 it is a recrystallisation subsequent to the formation of both pyroxenite and norite, and 

 hence a metamorphic character. If the whole series of charnockites be metamorphic 

 this development of hornblende may belong to a second metamorphic phase. Similar 

 evidence of metamorphism is reported from the Nilgiris. It is stated (p. 121) that 

 where the charnockite series is garnetiferous, the coarse-grained segregation or con- 

 temporaneous veins composed of quartz, felspar, and hypersthene also include garnet. 

 Like the hornblende the distribution of the garnet is not controlled by igneous 

 boundaries. 



It is to be noted that, in using the term norite for these rocks, Holland is quite 

 aware (p. 153) that they possess different appearance from olivine norite and augite 

 norite which can appear as normal dyke rocks. If the metamorphic character be upheld 

 this fact should not permit the retention of the name " norite." The norites, rich in 

 garnet, should be acknowledged as metamorphic rocks, because Holland considers 

 that the garnet, with its numerous characteristic inclusions, is formed from the 

 pyroxene. 



Where we find a description (p. 186) of pegmatoidal pyroxene plagioclase rocks in 

 the Nilgiri mass we may read further metamorphic evidence. These rocks occur in 

 lenticular masses which appear in trains along the same band of charnockite. The 

 lenticular shape is looked upon as the result of the pinching of a once continuous band 



