62 



DISCOVERY REPORTS 



The intermediate rocks of the Deception Island series are even more difficuh to match. The 

 oUgoclase-andesite (Table 3, col. 4) can be paralleled, and that not very closely, by an andesite from 

 the Sincholagua volcano in Ecuador (Table 3, col. F), and by a trachytic andesite from the Recent 

 lavas of the Modoc Quadrangle, California (Table 3, col. G). The bandaitic pillow-lava of Deception 

 Island (Table 3, col. 5) can be most closely compared with a hypersthene-augite-andesite from 

 Grenada, B.W.I. (Table 3, col. H); and less closely, at least in respect of the nak and k ratios, with 

 an andesitic ash from Cotopaxi, Ecuador (Table 3, col. I). It is to be noted that the Ecuadorian 



Table 3 . Intermediate lavas of Deception Island and comparable analyses 



4- 

 F. 



5- 

 H. 



I. 

 J- 



Oligoclase-andesite, Deception Island (Table i, col. 4). 



Pyroxene-andesite, Ceballos-chupa, Sincholagua volcano, Ecuador. A. Young, op. cit. supra, p. 24S. Quoted from 



Washington's Tables, op. cit. supra, p. 452. 



Trachytic andesite (Platy Andesite Group), south of Medicine Lake, Modoc Quadrangle, California. H. A. Powers, 



'The Lavas of the Modoc Lava-bed Quadrangle, California', Amer. Min. xvii, 1932, p. 292. 



Bandaite (hypersthene-augite-andesite), pillow-lava. Deception Island (Table i, col. 5). 



Augite-hypersthene-andesite, Grenada, B.W.I. J. B. Harrison, Rocks and Soils of Grenada, 1896, p. 10. Quoted from 



Washington's Tables, op. cit. supra, p. 466. 



Andesitic ash, Cotopaxi, Ecuador. J. W. Mallet, Proc. Roy. Soc. XLii, 1887, p. 2. Quoted from Washington's 



Tables, op. cit. supra, p. 764. 



Augite-hypersthene-andesite, Mt Kouragio, Aegina, Greece. H. S. Washington, 'A Petrographical Sketch of Aegina 



and Methana, Part III', J. Geol. in, 1895, p. 150. 



volcanoes have provided two of the comparable analyses in Table 3. It would appear that the andesites 

 of these volcanoes are more sodic than the usual run of Andean andesites. It is interesting to find, 

 also, that an augite-hypersthene-andesite from the Aegean region (Table 3, col. J) has some chemical 

 characters in common with the bandaite of Deception Island. 



It will be noted that all the Deception Island rocks and the comparable types dealt with in Tables 2 

 and 3 have been characterized by a ratio F'jM' greater than unity. In the remaining rocks of the 

 Deception Island series, the andesitic basalts (Table 4, cols. 6, 7), however, this ratio is less than unity. 

 The andesine-basalt (Table 4, col. 6) is closely comparable with another Ecuadorian lava, a basalt 



