Victorian Igneous J{o<-ks 289 



111^', un<l many dt' tlicse movomt'iits are uml<iul)tc'(lly of Kaiuozoic 

 age. Tlie Xi'wor Basalts of Victoria are mainly eonfined to the 

 faulted area of South-Westerii Victoiia. The (Ireat Valley of 

 Victoria is of the nature of a rift-valley, this area having lieen 

 faulted down since the deposition of the Jurassic rocks. Bass 

 Strait also represents another Kainozoic rift-valley. 



The earth movements in Victoria during" the Kainozoic period 

 were of the Atlantic coast type, and on Haiker's hypothesis we 

 should therefore expect to find i-ocks of the alkaline branch. It has 

 been shown that smh do dvvuv at Macedon (19), Coleraine (2.'5) and 

 Omeo {l^}, Ijut with them we must associate the calcic basalts. 



V. Petrographic Regions. 



We are now in a position to criticise Marker's generalisation on 

 the relationship of the alkali and calcic branches of igneous rocks 

 to tectonic movements in the light of the evidence to be derived 

 from a study of the Victorian igneous rocks. 



In the fii'st place, notwithstanding Barker's assertion that the 

 •characteristics of the two branches are too well known to need 

 recapitulation, there is distinct uncertainty as to which branch a 

 large number of rocks belong. In discussing the basalts of Skye 

 {6) Harker himself finds difficulty in their classification. He con- 

 siders that normally basalts belong to the calcic group, bvit that 

 in this case they show alkaline affinities in the presence of various 

 zeolites, including original analcime. 



The Heathcotian diabases are probably associated with fault 

 movement, but there is no evidence that they show the slightest 

 sign of alkaline affinities. Zeolites are plentiful in the basalts of 

 Collingwood, Flinders, and elsewhere in Victoria, and anorthoclase 

 is sometimes found to be present, but the few analyses that have 

 been pu])lished of the Victorian Kainozoic basalts agree very closely 

 with the composition of basalts from other jiarts of the world, and 

 there is absolutely no reason for placing them in the alkali branch. 

 Yet these rocks must be associated with fault movements. 



In our paper on the Macedon District (19) Professor Skeats and 

 the author advanced evidence in support of the genetic associa- 

 tion of the alkaline rocks of that area with the Kainozoic basalts of 

 Victoria. At the same time it was pointed out that similar asso- 

 ciations of alkaline rocks with basalts had been recorded by Daly 

 ^2) and Marshall (10). If this genetic relationship of alkaline 



