196 AUSTRALASIAN ANTARCTIC EXPEDITION. 



of charnockite, and in view of the Cape Denison phenomena this is quite consistent with 

 metaniorphic action. The pegmatoidal structure described between the felspar and 

 pyroxene in these rocks reads like a known metaniorphic structure, and the amphibolisa- 

 tion of the pyroxene certainly is. 



Finally, it may be pointed out that the so-called abnormal igneous features (p. 244) 

 find ready explanation on this metamorphic hypothesis. Whereas the granulitic 

 structure and the almost complete absencg of pronounced porphyritic crystals are 

 remarkable for large masses of igneous rock, they are normal features in large masses 

 which have been thoroughly recrystallised under kata zone conditions. The frequent 

 presence of garnet cannot be adequately explained by an igneous hypothesis supple- 

 mented by subsequent mechanical deformation, and the parallel arrangement of the 

 constituent minerals requires the action of stress after consolidation. If the pressure 

 during recrystallisation were wholly the hydrostatic type no foliation would result, but 

 such cannot be generally expected. The small amount of foliation denotes a weak 

 stress. 



An acknowledged metamorphic character can readily admit a variety like biotite 

 pyroxene gneiss referred to by Fermor,* and considered by Holland to be probably 

 an abnormal member of the charnockite aeries. 



3. THE " INFRAPLUTONIC ZONE" HYPOTHESIS. 



Could the conclusion concerning the metamorphic nature of the charnockite series 

 be avoided if we accept Fermor's conception of an infraplutonic zone ? In this hypo- 

 thesis Fermor postulates the existence of a shell in the earth's crust, situated below the 

 depth at which plutonic rocks consolidate, and characterised by garnets. The shell 

 must lie at considerable depths, and the temperature and pressure are very high. It 

 extends round the earth, and the whole of it is a potential magma.f 



Fermor's theory arises from the study of an area of garnetiferous and manganiferous 

 rocks which have been named the " Kodurite Series." In certain members of this series 

 Fermor discovered that a calculation of the specific gravities of the mode and norm 

 of the spandite rock (Ca-Mn garnet), and of kodurite (orthoclase, Mn garnet and 

 apatite), showed that the spandite rock occupied 20 per cent., and the kodurite 10 per 

 cent., smaller volume than its norm. Such indicates that the conditions favourable 

 to the formation of garnet rocks are those of high pressure. If high pressure conditions 

 have prevailed in the case of the kodurites, Fermor expects to find garnets in the various 

 rock series associated with the kodurites. As this is so, he then suggests that eclogite 

 must be a high pressure form of gabbro. It may be pointed out that eclogite has already 



* " Manganese Deposits of India," L. L. Fermor, pt. II., p. 245, Mem. G.S.I., 37. 



t " Preliminary Note on Garnet as a Geological Barometer and on an Infraplutonic Zone in the Earth's Crust " L. L. 

 Fermor, Rec. G.S.I. XLIII, pt. I., 1913. 



