ALKALINE ROCKS. 193 



The separate reports detail what has been done in Victoria 

 and New Zealand. Mr. Wearne's work in Queensland is fully 

 accounted for in his paper. I have now only to state what other 

 observations have been made on alkaline rocks. 



In 1909 I went down the South Coast as far as Bega on a 

 soil collecting trip. At the foot of Mount Dromedary occurs a 

 complex of basic igneous rocks of great interest, comprising quartz- 

 diorite, monzonite, orthoclase gabbro, essexite and other species. 

 At Brogo occurs a similar but smaller complex. Dr. Woolnough 

 has also informed me that he has had anorthoclase-granite from 

 Dromedary. I believe that these basic sub-alkaline rocks are the 

 plutonic equivalents of the hypabyssal orthoclase-diorites of 

 Milton, and of the volcanic sub-alkaline lavas of the Kiama- 

 Jamberoo area. As we pass from the geosyncline of the Sydney 

 basin towards the geanticline of Eden-Monaro and Gippsland 

 we get rocks of a more and more deepseated origin exposed by 

 erosion. Not having done any detailed work, I only propose to 

 indicate the problem. 



Early in 1909, Mr. Benson discovered alkaline riebeckite 

 trachytes at Murwillumbah. On a later visit I observed a dyke of 

 alkaline trachyte in the same locality. As Dr. Woolnough finds 

 the great bulk of the rocks of Mt. Warning to belong to a different 

 family, it would be interesting to find the relations of the alkaline 

 rocks there to the other rocks. 



Recently Professor R. A. Daly published an interesting paper 

 on the possible origin of alkaline rocks, in which he suggested 

 that they are differentiated from a normal magma which has been 

 fluxed by coming into contact with limestone. The theory is a 

 fascinating one and very plausible on physical, chemical and metal- 

 lurgical grounds, but it fails altogether in the Australian region 

 from the standpoint of field geology. Professor Daly makes it appear 

 that there are limestones in proximity to the Warrum bungles. Glass 

 House Mts., and Nandewars which is not the case, while the best 

 instance he could have chosen in support of his theory is omitted, 

 namely, the alkahne and sub-alkaline rocks of the Kiama-Jamberoo 

 area. To make this theory apply to Austrahan regions he will 

 have to assume mixture with deepseated limestones not outcropping 

 in the volcanic regions, an assumption just as impossible of direct 

 proof inmost localities as the one which I made in outlining my theory, 

 and which he condemns on grounds of insufficient evidence. I be- 

 lieve that future research will prove my theory well-founded and 

 applicable in many regions, and Daly's applicable in others, and a 

 compromise between them in most. Workers on alkaline rocks 

 will do well to look for evidence for and against each. The minerals 

 and inclusions of alkaline rocks will furnish the best clues. The 

 artificial preparation of the minerals of alkaline rocks would also 

 be helpful. 



