132 PROCEEDINGS OF SECTION C. 



11.— PRELIMINARY NOTE ON THE ALKALI ROCKS OF DUNDAS 



(VICTORIA). 



By H. S. SUMMERS, M.Sc, Lecturer and Demonstrator in Geology, University of Melbourne. 



Introduction. — The very suggestive paper by Dr. Jensen^ on 

 the origin of alkah rocks has led to increased interest in the occur- 

 rence of such rocks in Victoria. Professor Skeats^ has shown in his 

 presidential address at Brisbane that four areas are known inVictoria 

 in which alkali rocks occur, viz., Mt. Leinster area and Frenchman's 

 Hill, in Gippsland ; Macedon district, in Central Victoria, and the 

 Coleraine area in south-western Victoria. Anorthoclase felspar 

 occurs in some of the Victorian basalts, so that further microscopic 

 work may show that it is necessary to include some of these rocks in 

 the alkali series. Professor Skeats and the author paid a hurried 

 visit to the Coleraine area some two years ago, but there was not 

 sufficient time available to carry out any detailed work. During 

 the present year, in company with Mr. C. Wilson, I was able to spend 

 one of the vacations in the field, and these notes are a summary of 

 the observations made ; but it will probably require another visit 

 to the locality and further work in the laboratory before I will be in 

 a position to publish a detailed account of the petrographical 

 features of the area. 



Previous Literature. — In 1893 the late Mr. Dennant^ read a 

 paper before the Association at its Adelaide meeting, in which he 

 described various igneous rocks of south-western Victoria. Certain 

 rocks are described as containing sanidine felspar, and these were 

 shown to be associated with basic rocks containing abundant 

 olivine. The rocks were not named, and on the sketch map ac- 

 companying the paper are referred to as " Sanidine and Olivine 

 Rocks." 



In 1894 Mr. W. Ferguson*, of the Victorian Geological Survey, 

 made brief mention of the alkali rocks, and recorded the occurrence 

 of glacial conglomerate near Coleraine. 



The glacial conglomerates were further described by Mr. E.G. 

 HoggS in 1898 at the Sydney meeting of the Association, and in 

 his paper Mr. Hogg describes a dyke through Adam and Eve, near 

 Coleraine, as being trachyte, and briefly refers to other igneous 

 rocks in the area In the same year, 1898, Mr. Stirling^ reported 

 on portion of the Western District, but made little mention of the 

 volcanic rocks. 



An important contribution to the petrology of the alkah rocks 

 was a paper by Mr. Hogg'^ read before the Royal Society of Victoria, 

 in 1899, in which he describes more fully the dyke at Adam and Eve. 

 The felspar is identified as sanidine, and this mineral, together with 

 apatite and opaque matter and some glass, is stated to constitute 



1 Proc. Linn. Soc. N.S.VV., Vol. XXXIII., pt. 3, 1908, p. 491. 



2 ^..4.^.5. Brisbane, 1909, p. 173. 

 SA.A.A.S., Adelaide, 1893, p. 389. 



iGeol. Survey. Vict. Prog. Rep., No. VIII., 1894, p. 58. 



5A.A.A.S. Sydney, 1898, p. 356. 



GGeol. Survey. Vict. Prog. Rep. No. IX., 1898, p. 85. 



7 Proc. Roy. Soc. Vict., Vol. XII. (N.S.), Pt. I., 1899, p. 90. 



