114 



PETROLOGY OF THE ALKALINE ROCKS 



period. The intersertal base consists of a granulite mass of brown titaniferous augite 

 and magnetite in almost idiomorphic grains, giving the whole rock almost a panidio- 

 morphic structure. A little interstitial, colourless, and isotropic material is present, 

 probably sodalite or analcite. 



J. 26 (1935). Limburgitic Basalt, Hut Point. — Texture.— Microporphyritic hiatal, 

 dopatic; hyalopilitic fabric near to diabase structure. 



Composition. — Magnetite forms about 30 per cent., titaniferous augite about 

 45 per cent., and alkali- felspar about 15 per cent. These minerals belong to the second 

 generation, and in the interstices between them we have fillings of analcite or sodalite. 

 About 10 per cent, of the rock consists of olivine in small hypidiomorphic phenocrysts. 

 Nepheline also appears to be present. 



The rock is a very basic one, and may be called limburgitic basalt allied to basanite. 



Two rocks, viz., J. 49 from Cape Barne and J. 36 from Mount Bird, are allied to 

 kulaite, but must be put in this group as felspar olivine basalts. 



J. 49 (1958), Cape Barne. This is a black rock, porphyritic in white phaneric 

 felspars. 



Texture.— Porphyritic hiatal, sempatic, megaphyric, with aphanitic hyalopilitic base. 



TABLE III. ANALYSES OF BASIC ROCKS 



