290 H. S. Summers. ■ 



rocks witli basalts be correct, then Marker's generalisation fails 

 unless Ave assume that the basalts show alkaline affinities. 



Turning to the granitic-dacite series of Victoria we see that they 

 are associated with movements of the Pacific coast type, and con- 

 sequently should be expected to belong to the Calcic Branch. 



The analyses of the dacites from Macedon show an average of 

 2.55 per cent, of potash, 2.62 per cent, of soda, and 4.03 per cent, 

 of lime, so that they must be classed as belonging to the Sub-alkali 

 Group (Iddings), which is equivalent to Marker's Calcic or Pacific 

 Branch. 



In the same way the granodiorites may be shown to belong to the 

 Sub-alkali Group. 



The analyses of the granites from Dog Rocks, Cape AVoolamai, 

 Gabo Island and Mt. Buffalo show the following percentages : — 



Dog: Cape Gabo Jit. 



Rocks. Woolamai. Island. Buffalo. 



KjO - 5.27 4.76 4.06 4.89 



Na,0 - 3.30 3.00 3.38 3.12 



CaO - 0.41 .65 1.31 0.84 



An examination of a section of the granite from the Dog Rocks 

 shows that it contains two felspars, one of which is orthoclase and 

 the other a triclinic form showing exceedingly fine twin lamellae and 

 undulose extinction, and which seems referable to anorthoclass. 

 As this rock contains 8.57 per cent, of alkalies and only 0.41 per 

 cent, of lime, it is quite impossible to stretch the definition of the 

 Calcic Branch to include a rock of this composition. The granites 

 of Cape Woolamai. Mt. Buffalo and Gabo Island must also be 

 classed as belonging to the Alkaline Branch. 



The variation diagram (Fig. 3) shows that if any reliance can be 

 placed on variation diagrams, then the alkaline granites are 

 genetically related to the subalk aline or calcic dacites and grano- 

 diorites, and that there is a gradual passage from alkaline to 

 calcic types in the granitic-dacite series of Victoria. 



It will be seen that the above evidence is in distinct opposition 

 to Marker's generalisation. The calcic diabases of Meathcote and 

 the calcic basalts of the Kainozoic Period are to be associated with 

 movements of the Atlantic coast type and the alkaline granites of 

 the Dog Rocks, Cape Woolamai and elsewhere, accompany move- 

 ments of the Pacific coast type. 



The conclusion then is that Marker's generalisation in its present 

 form fails when applied to the elucidation of the association of 

 igneous rocks and earth movements in Victoria. 



