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THE PETROLOGY OF THE GRANITIC MASS OF CAPE 

 WlLLOUGHBY, KANGAROO ISLANDI-PART I. 



By C. E. Tilley, B.Sc., A.I.C., 



Demonstrator in Geology and Mineralogy, University of 

 Sydney. Deas-Thomson Scholar in Geology, 1919. 



(Communicated by Professor Walter Howchin.) 



[Read September 11, 1919.] 



Plates XXX. and XXXI. and 2 Maps. 



Contents. 

 I. Introduction. 

 II. General Description. 



III. Characters of the Rock Types — 



(a) The Main Granite. 



(b) The Minor Intrusions. 



IV. The Pink Aplite and its Products of Pneumatolysis. 

 V. The Nature and Composition of the White Pegmatite. 



VI. The Relations of the Rock Types. 

 VII. General Discussion. 



I. Introduction. 



The imposing granite headland of Cape Willoughby 

 forms the easternmost extremity of Kangaroo Island. From 

 the standpoint of petrology this locality has received little 

 attention, and in the previous literature dealing with this 

 area brief reference only is made to the intrusion. This 

 literature is : — 



(i.) Howchin, W. : Trans. Roy. Soc. S. Austr., vol. 

 xxvii., 1903, pp. 80-83. 



(it.) Wade, A.: Bull. No. 4, Geol. Surv. S. Austr., 

 pp. 20 and 21. 



In addition the writer has described certain quartz 

 tourmaline nodules from this area. (1 ) 



Howchin, while investigating the geographical extent 

 of the late Palaeozoic (Permo-carboniferous) glacial deposits 

 on Kangaroo Island visited Cape Willoughby, and in his 

 subsequent paper briefly refers to the granite and its minor 

 intrusions. W T ade mentions its intrusive character into the 



(1) Tilley: Trans. Roy. Soc. S. Austr., 1919, p. 156. 



