216 PROCEEDINGS OF SECTION C. 



Results such as these can only be attributed to the gigantic 

 earth movements which accompanied, or perhaps preceeded the 

 invasion of the sedimentary crust by the plutonic magmas. 



It will now be evident that there are two well mai^ked groups 

 of crystalline schists in the Omeo district. The phyllites and 

 mica-schists which have resulted from the metamorphism of 

 sediments, and the mica-schists and gneisses which have been 

 produced by the metamorphism of igneous rocks. Both these 

 groups have been metamorphosed by the same general agents, 

 namely, by pressure metamorphism, and in connection with it 

 also chemical action producing molecular re-crystallization. The 

 general result has been that a twofold set of crystalline schists 

 have been produced, to which the general term Regional Meta- 

 morphic Schists may still be applied. 



In the part of the district which I have taken as the text for 

 this paper, these two groups are found in places apart from each 

 other. 



Comparing these two occui^rences with the apparent sequence, 

 or passage from the normal argillites of the district through mica- 

 schist and gneiss, to the massive quartz diorites and granites, at the 

 margins of the metamorphic areas, the conclusion seems to be 

 justified that future examination will show that in such places, as 

 for instance at the Upper Dargo, there is a break between the 

 banded gneisses and its mica-schists, or even in the latter, and 

 that the former are not metamorphosed sediments, but the 

 margins of the intrusive plutonic rock -masses altered by pressure 

 metamorphism . 



I must, however, point out here, that the gneisses which are to 

 be found in places bordering intrusive masses of diorite, are 

 probably not in all cases due to pi'essure metaiuorphism. That is 

 to say, they have not been produced by the re-arrangement 

 through pressure of already solidified and rigid rock masses, such 

 as was the case with the rocks which I have described. For 

 instance, there are in the Swift's Creek area, rocks which are 

 almost fantastically constructed, yet parts of the adjoining rock- 

 masses are crystalline granular. Such gneisses as these difier 

 most materially from the bedded and banded gneisses which I have 

 described. Pressure has probably had to do with their structure, 

 but pressure acting upon a partly crystallized magma, and not 

 upon a rock already crystallized throughout. 



In connection with the effects of pressure-metamorphism, which 

 are described by a study of the crystalline schists at Omeo, it 

 becomes important to enquire in how far the smaller and later 

 irruptions of plutonic rooks may have influenced the final results. 

 An example of such a later irruption is given by the Frenchman's 

 Hill, a mount which rises to some height, not far from the great 

 fault, and on its south-west side. The following particulars are 

 the condensed results of an investigation upon which I have spent 

 some time, but the details of which are not yet published. 



