﻿

Vol. 66.] AND DACITES OF THE DANDENONG DISTRICT. 451 



Victorian geology. The following are the principal papers in which 

 the dacite series is more or less directly discussed : — 



(1) A. E. C. Selwtn. Rep. Geol. Surv. Vict., Nov. 1854, pp. 3-10. 



(2) A. W. Ho witt. 'Notes on the Geological Structure of North Gippsland ' 



Geol. Surv. Vict. Progr. Rep. iv (1877) pp. 75-117. 



(3) R. A. F. Mueeat. ' Geology & Physical Geography of Victoria' 1895. 



(4) J. Stieling. Geol. Surv. Vict. Progr. Rep. Nos. 8 & 9 (1899) pp. 28-29. 



(5) A. E. Kitso>-. Geol. Surv. Vict. Month. Progr. Rep. No. 11, 1899, pp. 9-18. 



(6) V. R. Stirling. Geol. Surv. Vict. Month. Progr. Rep. No. 1 (n. s.) 1899, 



pp. 10-11. 



(7) J. W. Geegoet. ' The Geology of Mount Macedon (Victoria) ' Proc. Roy. Soc. 



Vict. n. s. vol.xiv, pt. ii (1902) pp. 385-217. 



(8) Ian M. Suthebland. 'The Relations of the Granitic & Lower Palaeozoic 



Rocks near Dandenong ' Ibid. vol. xvii, pt. i (1904) pp. 112-17. 



(9) F. Chapman. ' Victorian Naturalist ' vol. xx (1904) p. 127. 



(10) A. E. Kitson. Ibid. vol. xxii (1905) p. 128. 



(11) H. S. SuiiaiEES. ' The Cherts & Diabase Rocks of Tatong ' Proc. Roy. Soc. 



Vict. n. s. vol. xxi, pt. i (1908) pp. 240-46. 



(12) Id. ' Geology of the proposed Nillahcootie Water-Conservation Area ' Ibid. 



pp. 285-301. 



(13) H. C. Richaeds. ' On the Separation & Analysis of Minerals in the Dacite 



of Mount Dandenong (Victoria) ' Ibid. pt. iii (1909) pp. 528-39. 



(14) E. W. See ats. Pres. Addr. Sect. C. Aust. Assoc. Adv. Sc. (Brisbane) 1909. 



Selwyn (1) and Murray (3) described the series as ' traps/ 

 regarded them as intrusive rocks of Palaeozoic age, and expressed 

 the view that in some places a gradual passage could be traced 

 between them and the granitic rocks. Prof. Gregory (7) was the 

 first to describe them as dacites, and maintained that at Macedon 

 they are quite distinct in composition and origin from the grano- 

 diorites and are entirely unaltered near the contact with these. 

 He regards the dacites as volcanic rocks poured out over a denuded 

 Palaeozoic platform of sedimentary rocks and granodiorite, and 

 maintains that they are far younger than the granitic rocks and 

 may be of Lower Kainozoic age. 



Since 1905 I have been investigating the relations between the 

 dacites and the granodiorites in Victoria, and the evidence that I 

 have obtained south of the Dandenong Hills, at Warburton, and 

 at Marysville, has led me to draw different conclusions from those 

 of previous observers. Mr. Summers (11 & 12) has come to con- 

 clusions similar to mine, as the result of evidence obtained in the 

 Strathbogie ranges ; while detailed examination of the Macedon 

 district by Mr. Summers and myself has afforded similar results. 

 In a Presidential address on the volcanic rocks of Victoria (14), 

 given by me to the Geological Section of the Australasian Association 

 for the Advancement of Science at the Brisbane meeting in January 

 1909, 1 summarized the evidence and conclusions arrived at in the 

 above areas. The detailed evidence from the Macedon area will 

 appear shortly in a ' Bulletin ' of the Geological Survey of Victoria. 



Mr. liichards's work (13), undertaken at my suggestion, deals 

 with the chemical composition of the normal dacite and with the 

 separation and analysis of the ferromagnesian minerals of variable 

 composition which occur in it. It provides valuable material for 

 the discussion of the interesting mineralogical changes which tbe 

 dacite has undergone at its contact with the granodiorite. 



