106 AUSTRALASIAN ANTARCTIC EXPEDITION. 



5. GEOLOGY OP THE LIZARD AND MENEAGE. Flett and Hill.* 



This memoir contains an account of the metamorphic region of the Southern Lizard 

 surveyed and described by Dr. Flett. In this area an extraordinary number of rock 

 types are developed which have been the object of study of a large number of workers. 

 The earlier work has been summarised by Flett and incorporated in his own work, so 

 that a very full and clear description of the rocks and the rock problems is presented. 

 One, however, turns to the memoir to discover if any recognition has been made of true 

 metamorphic types, and the general impression obtained from the memoir is that the 

 rock problems have been treated rather from the standpoint of igneous rocks and of 

 rock magmas. It appears that the metamorphic character of the rock is considered 

 to be of subsidiary importance in comparison with its primary nature, and the value 

 of some of his conclusions is thereby lessened. 



The serpentine, one finds, is looked upon as a modified igneous rock. It is continually 

 referred to as the intrusive body, and there is only occasional reference to the peridotite 

 from which it is derived. The serpentine in all cases is considered (p. 80) as a 

 weathered or decomposition product of olivine. This is the recognised origin of 

 serpentine in many cases, and for this reason Grubenmann says']" that the position of 

 serpentine among the crystalline schists, from which normal weather products are 

 excluded, is doubtful and uncertain. Nevertheless, Grubenmann considers that 

 certain occurrences must be included therein, and, therefore, creates the serpentine 

 family in his classification of the crystalline schists. It seems to us that Flett has 

 produced strong evidence for the similar inclusion of the Lizard serpentine. 



We cannot agree with Flett that there is any reason (p. 97) to think that the main 

 serpentinisation of the Lizard peridotites took place at a comparatively late period of 

 their history, though there may be some development of serpentine in subsequent 

 weathering, as there is even in the example of primary serpentine recorded by 

 WeinschenckJ, and referred to by Flett (p. 97). Subsequent veins of chrysotile which 

 are unaffected by the schistosity seem to me to have very little bearing on the matter. 

 At Cape Denison there are numerous quartz segregation veins, independent of the 

 foliation, which may contain large and beautiful crystals of epidote, while epidote may 

 also appear along any joint plane of the gneisses and schists. These formations of 

 epidote are clearly subsequent to the development of foliation, yet no one would assume 

 from this that the formation of epidote in the amphibolite and schists was subsequent 

 to the development of foliation. In fact the epidote in some schists takes definite part 

 in the foliation, and has been proved to be a definite part of the mineral composition 

 of the amphibolite series. 



* "Memoirs of the Geological Survey. England and Wales." Sheet 359, 1912. The numbers placed in brackets in 

 the following have reference to pages in this memoir unless a special reference is given, 

 t Op. cit., vol. II., p. 113. 

 t " Spezielle Gesteinskunde," 2nd edit., 1907. p. 184. 



