Victorian Igneous Rocks. 261 



Sections of the granitic rocks near Bulla show that tliese rocks 

 are at the alkalic end of the granodiorites. 



Professor Skeats (17) has described the rock from Station Peak, 

 in the You Yangs, as a granite containing anorthoclase. 



Exceedingly similar in the hand specimen and under the micro- 

 scope to the Station Peak granite, but somewhat finer in grain, is 

 the granite from the Dog Rocks near Geelong. 



Microscopical examination shows tliat the rocks from Cape 

 Woolamai, Gabo Island, and Mt. Bviffalo are granites, and are easily 

 •distinguishable from the granodiorites of Central Victoria. This 

 difference in the microscopial characters led to the belief that there 

 were two types of granitic rocks in Victoria, which were quite 

 •distinct in their chemical characters, and had no genetic relationship 

 with one another. At first sight chemical analyses, to be quoted 

 later, seem to uphold this view. The granodiorites are intruded 

 into both the Ordovician and Silurian sedimentary series, whereas 

 .at present no true granitic rocks are known within the Silurian 

 area. This led to the view that whereas* the granodiorites were post- 

 Silurian, the granites might possibly be pre-Silurian. 



There is no exposed contact between the granites of the You-Yangs 

 or the Dog Rocks with fossiliferous sediments, but there is little 

 doubt that these granites are related to those of Maude, whicli are 

 intruded into sandstones and slates belonging to the Darriw'ell 

 horizon of the Lower Ordovician. The Mt. Buffalo granite is in- 

 truded into the Upper Ordovician. 



Evidence, however, will be adduced from a study of chemical 

 analyses of some of these rocks to show that the granites and 

 granodiorites are gentically related to one another. 



(c) Lily dale Devonian Series. 



Recently Mr. M. Morris has been working on a series of igneous 

 rocks which occur in the neighbourhood of Lilydale. Analyses of 

 four of the types have been made at the Mines Department Labora- 

 tory, and these are of considerable interest owing to their variation 

 from the normal dacites of the Dandenong Ranges, with which they 

 are intimately connected. Mr. Morris has kindly allowed mo to 

 use these analyses, but no description of the microscopical characters 

 or field relations can be given here. 



(d) Macedon Kainozoic Series. 



During the Kainozoic Period Victoria was the centre of intense 

 vulcanicity. Extensive flows of basalt covered a considerable area 

 of Southern Victoria, Avhile isolated patches are fairly widely dis- 

 tributed throughout the State. 



