VI. Age of tlie Intrusions. 

 VII. Contact Metamorphism. 



(1) Micaceous quartzites away from the intrusions. 



(2) Inclusions in the porphyritic granite. 



(3) Contact metamorphism at Rosetta Head. 



(a) Andalusite mica schist. 

 (h) Cordierite mica schist. 



(c) Cliff section. 



(d) Impregnation at the immediate syenite 



contact. 

 VIII. Summary. 

 'IX. Acknowledgements. 



1. Introduction. 



In the literature of South Australian geology the country 

 arou.nd Encounter Bay has received a certain amount of 

 attention principally on account of the very marked evidences 

 of the Permo-Carboniferous glaciation which abound there- 

 abouts, (i) Of systematic petrological investigations of the 

 igneous rocks there are, however, very few records. A brief 

 petrographical description of a biotite granite from Port Victor 

 has been given by J. C. Moulden,(2) who also describes an 

 axinite amphibolite from Rosetta Head. H. W. GartrelK^^ 

 investigated the chemical and optical properties of the felspar 

 phenocrysts of the granite, and Dr. Chewings(^) briefly 

 described a uralitic diabase from Port Elliot. 



The field work on which the present paper is based was 

 carried out some years ago while the author was Acting- 

 Lecturer in Petrology in the University of Adelaide. A few 

 visits were made to the localities on the mainland where 

 outcrops of the igneous rocks occur, but it was found imprac- 

 ticable to visit the granitic islets lying off the coast, except, 

 of course, Granite Island, which is artificially connected with 

 the mainland. Unfortunately, since the laboratory .work was 

 undertaken in S3^dney no opportunities have been available 

 of revisiting the localities, and certain questions requiring 

 further field examination, which have presented themselves in 

 the course of the work, have had to remain uninvestigated. 

 This fact, coupled with the loss of a number of specimens in 

 transit to Sydney, must be the excuse for any incompleteness 

 in the present paper. 



(DHowchin: Trans. Roy. Soc. S. Austr., 1904, 1906, 1910, 

 etc.; Howchin : Geology of South Australia, Adelaide, 1918. 



(2) Trans. Roy. Soc. S. Austr., vol. xix., 1894-5, p. 70. 



(5) Trans. Roy. Soc. S. Austr., vol. xxvii., 1903, p. 256. 



(4) Ein Bqitrage zur Kenntniss Geologie und Petrologie Snd 

 und Central Australiens, Heidelberg, 1894. 



