10 AUSTRALASIAN ANTARCTIC EXPEDITION. 



Cape Denison and its associated basic dykes. Twenty miles further east again, the meta- 

 morphosed sediments appear again at Cape Gray in the form of garnet cordierite gneisses 

 and garnet felspar gneisses. Inland from Cape Gray granitic areas have existed at 

 Madigan Nunatak and Aurora Peak. These facts are illustrated in the accompanying 

 section (fig. 1). 



In the section the granitic mass at Aurora Peak is assumed to be intrusive into 

 the original sediments, because altered granitic dykes appear on Stillwell Island and 

 Cape Pigeon Rocks cutting the garnetiferous gneisses. The altered granitic dykes 

 are not necessarily to be associated with the primary granitic masses of Aurora Peak 

 and Madigan Nunatak. The presence of tourmaline in the Cape Hunter phyllites is the 

 only evidence available for representing the intrusive nature of the Cape Denison grano- 

 diorite gneiss. 



The outcrops dealt with are isolated areas extending over 60 miles of country. 

 Over this great distance it is only to be expected that varying conditions of meta- 

 morphism would be found. On the west, at Cape Hunter, we have dominant epi-zone 

 metamorphism. At Cape Denison the metamorphic conditions are intermediate between 

 those of the epi zone and meso zone of metamorphism, with variation in both directions. 

 The amphibolites which are completely recrystallised rocks sometimes approach the 

 character of meso zone rocks and sometimes are more like epi zone rocks. On the Cape 

 Gray Promontory, where the garnetiferous gneisses abound, and at Madigan Nunatak 

 and Aurora Peak evidence of kata zone metamorphism is found in all cases. At Madigan 

 Nunatak very remarkable epi zone metamorphism is superimposed upon the kata zone 

 metamorphism, while between Madigan Nunatak and Cape Gray and at Aurora Peak 

 meso zone metamorphism is superimposed upon the kata zone metamorphism. There 

 is, therefore, quite a distinct regional distribution of the metamorphic products of 

 Grubenmann's three metamorphic zones and an argument in support of the general 

 conception produced. 



The detailed studies of the dyke series at Cape Denison and at Cape Gray have 

 produced some extraordinary results. In these, considerable use has been made of 

 the Rosiwal method of volumetric rock analysis for the purpose of obtaining relative 

 mineral composition of different specimens. The absolute mineral composition could 

 only be obtained by three determinations in three planes at right-angles a process 

 too tedious to be of any service. Yet the mineral composition of schists can be com- 

 pared with advantage in rock sections which have been cut from a constant direction 

 relative to the plane of schistosity. 



The Cape Denison dyke series ranges from epidote biotite schists at Azimuth Hill, 

 on the western part of Cape Denison, through biotite amphibolites to amphibolites 

 on the eastern side. Lawsonite has been detected in several cases, and lawsonite 

 amphibolites have been described. In the mineral composition of the series it is found 

 that the percentages of epidote and biotite vary sympathetically and inversely with 



