194 AUSTKALASIAN ANTARCTIC EXPEDITION. 



of the term dynamo metamorphism and his introduction of the terms piezo contact 

 metamorphism, etc. It must now be considered a fundamental fact that mechanical 

 structures are often absent in thoroughly recrystallised rocks. We have elsewhere 

 argued that the gneissic foliation in granites and similar rocks is always a metamorphic 

 feature in that it involves a rearrangement of crystals after, not before, consolidation. 

 We reached this conclusion because stress is considered to be an essential factor in its 

 production. Holland acknowledges the action of stress in saying (p. 125) that " the 

 crystals are arranged with their long axes at right angles to the direction of maximum 

 pressure." But when he adds " before consolidation " he is implying the action of a 

 stress through a liquid which is impossible. Holland's interpretation of the foliation 

 and banding has produced the chief difficulty in the determination of the charnockites 

 as metamorphic rocks. 



If this difficulty be removed there is no barrier to the interpretation of the 

 charnockites, like the Antarctic rocks, as a suite of igneous rocks that have suffered 

 complete recrystallisation under the conditions of the kata zone of metamorphism. 

 The demonstration of the primary igneous character by the form and structure of the 

 great massif, by the existence of dykes and apophyses proceeding from the main mass 

 and by the presence of included fragments of foreign rocks, is unaffected by the 

 acknowledgement of kata zone metamorphism. Nor is the chemical and mineralogical 

 evidence affected. Eecrystallisation under kata zone conditions (high uniform pressure, 

 dominating largely over stress and high temperature) does not destroy the dominating 

 igneous structures, e.g., the dyke structures at Cape Gray are so wonderfully clear that, 

 foliation being almost absent, no metamorphism was suspected in the field. Observation 

 of destroyed dyke structures are found restricted to areas where strong stress is evident. 

 It seems to us that a metamorphic history applied in general to the Charnockite series, 

 together with a double metamorphic history in those cases where mechanical structures 

 are evident, satisfies the recorded evidence including the supposed igneous abnormalities. 



The inclusion of rounded blebs of quartz in the felspar (quartz de corrosion) is a 

 metamorphic structure analogous to the case of rounded blebs of quartz or felspar in 

 the hornblende. The dissociation of felspar into microperthitic intergrowths is frequently 

 associated with metamorphism, and it is also to be noted that the hypersthene is 

 associated with a similar greenish alteration product in both the Indian and Antarctic 

 rocks. 



We are also inclined to read further evidence of recrystallisation after the primary 

 consolidation of the associated rocks in the frequent observation of crystalline continuity 

 across junctions. Sections cut across the junction of quartz felspar veins (p. 145) which 

 cut across the charnockite and which bear the same family likeness, show no abrupt 

 junction but a line of interlocking crystals. The same crystalline continuity is present 

 across the junction of quartz veins in the norite (p. 157), across the junction of pyroxenite 

 and norite, and across the junction of tongues of charnockite (p. 226) which ramify 

 the biotite gneiss, while there is a gradual passage from charnockite to garnetiferous 



