60 AUSTRALASIAN ANTARCTIC EXPEDITION. 



yield the high potash percentage of biotite, and, if we postulate sufficient felspar to 

 supply the alkali, there would be insufficient magnesium or iron for the hornblende 

 and biotite. If we ignore this difficulty and still assume an augite xenolith, we raise 

 further difficulty in recalling that hornblende, or biotite with epidote, is the normal 

 metamorphic equivalent of augite in this series. The amount of epidote in this schliere 



is scarcely appreciable. 



f 



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A A AA/ \A A AAA AAAA 



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Fig. 6. 



629. Amphibolite, Cape Denison. 

 640. Chlorite schist, Cape Denison. 

 415. Epidosite, Cape Denison. 

 4. Biotite hornblende schist, Cape Denison. 



The original dolerite may have contained some biotite and, therefore, it might be 

 conceived as possible that the schlieren are the metamorphosed equivalent of primary 

 segregations composed of two-thirds biotite and one-third augite. Such would be a 

 very extraordinary xenolith, and I am not aware that we have any information of such 

 a type of cognate xenolith. Here it is quite apt to remark that it is fundamentally 

 wrong to insist on explaining curious metamorphic features by reference to abnormalities 

 in the primary rock, igneous or sedimentary. The biotite and the hornblende throughout 

 the series have been developed during the metamorphism, and it is quite reasonable 

 to view these schlieren as true metamorphic products. The beautiful parallel arrange- 

 ment of the biotite and the hornblende strongly suggests that this rock owes its origin 

 to the metamorphism and nothing else. 



A biotite schliere is recorded in the band from which specimen No. 630 was collected 

 as the normal rock of the band. The schliere occurred in a broad bulge 12ft. or 15ft. wide, 



