178 

 analysis of typical basalts in Victoria, and with Mr. Daly's 



,ge basalt 



A. 



B. 



C. 



SiO, 



48-00 



48-84 



46-95 



Al 2 6 3 



14-11 



15-90 



14-37 



Fe 2 3 



5-61 



5-23 



1-37 



FeO 



6-11 



6-30 



9-52 



MgO 



8-81 



6-38 



9-74 



CaO 



8-68 



9-15 



10-04 



K 3 



3-01 



3-05 



3-49 



Na 2 



1-25 



1-46 



1-53 



H 3 6 + 



•73 



fl-60 



•52 



H 3 0- 



•80 



•10 



TiO„ 



2-20 



1-35 



2-04 



Mn6 2 



•13 



•29 



— 



PiO, 



•50 



•45 



•46 



99-94 



100-00 



100-13 



A. Average of six basalts, Camperdown District, Victoria. 



"Geology of the Camperdown and Mount Elephant 

 Districts," Mahony and Grayson, Mem. Geol. Sur. 

 Vict., No. 9, 1910. 



B. Average basalt analysis. "Igneous Rocks and their Origin," 



R. A. Daly, 1914, p. 315. 



C. Mount Gambler vesicular olivine basalt. E. R. Stanley 



(Ref. No. 6). 



Stanley also published microscopic descriptions of the 

 slaggy and vitrophyric types of lava, found at Mount Gam- 

 bier, and concludes that, on the evidence presented, the 

 Mount Gambier lavas are closely related to those of Western 

 Victoria. The comparison with Mahony and Grayson's 

 analyses, and with other subsequent analyses of Victorian 

 basalts, strongly supports this conclusion, as does other evi- 

 dence later referred to. 



(b) The Fragmentary Material and its Distribution. 

 Apart from the brief effusive phase above described, the vul- 

 canicity was wholly of the explosive type. Possibly the 

 occurrence of the outburst in the centre of a strongly water- 

 bearing series had some bearing on this fact. The ejecta- 

 menta of which the cinder cones were built, and of which the 

 finer particles were widely distributed, consists of lapilli and 

 ash with but a small representation of coarser scoriaceous 

 material. In this respect the materials and the cones more 

 closely resemble those of Tower Hill, in Victoria, than the 

 more abundant scoria cones, such as Mounts Warrenheip, 

 Buninyong, etc. 



