METAMORPHIC ROCKS OP THE OMEO DISTRICT, GIPPSLAND. 219 



in places with a regeneration of quartz and felspar in the graphic 

 manner. Moreover there are indications of alterations of tem- 

 perature in the partial al^sorption of some of the minerals, as for 

 instance of felspar, and of the production of muscovite from the 

 resulting solutions. Such observations as these may be made as 

 to the aplites in less degree, but not as to the younger rocks of this 

 irruption. The orthophyrs show that they contracted so much in 

 consolidating that the ends of tlie felspar crystals and the grano- 

 phyric ground nass left spaces which were filled by hasmatite. The 

 few metamorphic changes were endomorphic, proceeding from the 

 action of the intrusive masses themselves, and not from external 

 causes. This, therefore, leads to the conclusion that the irruption 

 of the Frenchman's Hill area was subsequent to the action of the 

 forces which metamorphised the plutonic rocks at Greenwattle 

 Creek into gneisses by pressure. 



CONCLUSION. 



In the preceding sections I have dealt with only a part of the 

 metamorphic area which covers so great a length in Eastern 

 Victoria. I have bi'iefly described the principal features of the 

 crystalline schists, and of the plutonic I'ocks found associated 

 with them, and I have but superficially touched upon the questions 

 raised by the consideration of these rocks. My object has been 

 to record briefly the observations which I have made, and the 

 conclusions to which these observations have led me, leaving more 

 complete details to be given at some future time. 



The time requisite for the conversion of the sedimentary and 

 plutonic rocks at Omeo, into crystalline schists, appears to have 

 been one of very extended dui'ation, of which the measure is that 

 of a geological period. The manner in which the great thickness 

 of ancient oceanic rocks has been built up in the district south- 

 east of Omeo, the mode in which the Middle Devonian marine 

 limestones rest comformably upon them, and the total absence in 

 Gippsland of any sedimentary beds which can be referred to the 

 Lower Devonian, long ago suggested to me that the latter period 

 was one of terrestrial condition."*^ 



The great earth movements which produced the alteration of 

 the Silurian sediments into argillites and crystalline schists also, 

 as is shown by the structure of the Omeo district, brought about a 

 great elevation of the earth's crust. It was probably a time of 

 mountain making and of the marking out of the first outline of 

 the Australian Alps. 



Along the eastern and western boundaries of the metamorphic 

 area, there is at Omeo evidence of enormous pressure exerted upon 

 the sediments, and upon the plutonic rocks adjoining them. 



* Notes on the Physical Geography and Geology of North Gippsland. Quart. Journ. 

 Geol. Soc, XXXV. p. 1. 



