REPORTS OP RESEARCH COMMITTEES. 305 



SECTION C. 



2. Alkaline Rocks Committee. 



{By Professor Ernest W. Skzats, D.Sc. A.R.C.Sc, F.G.S., Secretary 

 to the Committee.) 



Since the last meeting of the Australasian Association for the 

 Advancement of Science in Melbourne in 1913, increase of know- 

 ledge of alkaline rocks in Australia has, so far as has come under 

 my notice, occurred in Queensland, Tasmania, and Victoria. 



Queensland. 



In this State. Professor H. C. Richards, D.Sc, has made two 

 important contributions to our knowledge of alkaline rocks. In 

 an exhaustive paper on the Volcanic Alkaline Rocks of South- 

 Eastern Queensland\ he has made known the existence of 

 extensive areas of trachytic rocks with trachytic pitchstones as 

 selvages to lava flows and of associated trachytic tuffs. These 

 occupy wide areas in South-eastern Queensland, and always occur 

 between an older and a younger series of basaltic flows. The reck 

 types are fully described and analyzed. More recently he has 

 described an additional area of trachytic and asscciated rocks 

 from near Springsure, in Central Queensland-. In this paper 

 the same association of alkali rocks intercalated between an 

 older and newer basaltic series was found. Again, too, is noted 

 the association of , pitchstone as a glassy selvage at the base of a 

 flow of alkaline trachyte. The rocks consist of trachytes, trachytic 

 tuffs, pitchstone, and, in addition at Virgin Reck, Professor 

 Richards records the occurrence of a phonolite containing 

 anorthcclase, sanidine, and nosean, augite granules and magnetite. 

 An analysis shows 67.32% of SiO,. 10.61% of alkalies divided 

 between Na,0 5.32% and K.O 5.29%. The bearing of the field 

 occurrence of these rocks on the various theories of the origin of 

 the alkaline rocks is discussed. In the same paper attention is 

 recalled to the fact that Dr.' Jack, in the Annual Report of the 

 Mines Department, Queensland, in 1894, described as trachyte 

 certain " necks " such as Mt. Gamia, Pigeon House, St. Peter and 

 Little St. Peter 



Tfis/iut/iui . 



The only advance in knowledge from Tasmania which has come 

 under my notice is in a paper by the writer on the age of the 

 alkali rocks of Port Cygnet, and the d'Entrecasteaux Channel 

 m South-east Tasmania. 3 For long the age of the interesting 

 alkali complex at Port Cygnet and other localities in South-east 



1. Proc. Roy Soc, Queensland, Vol. XXVII.(2), 19i6. 

 2. Proc. Roy. Soc. Queensland Vol. XXX. 

 3. Proc. Roy. Soc, Vict., Vol. XXIX. (n.s.), Part II. March, 1917. 



