Metamorphic and Plutonic Rocks at Omeo. 129 



surface accumulations have led to the erroneous belief, which 

 for long I also shared, that there is at Omeo a passage from 

 the granitic rocks to the lower palaeozoic sediments, and 

 that therefore the former are the completely metamorphosed 

 forms of the latter. 



Where the ^-ranitic rocks have no margin of sjneiss at 

 their contact with the sediments, and where the latter have 

 undergone very great molecular recrystallisation, tliedifl&culty 

 of a true diagnosis is very great, and questions arise whicli 

 may require possibly to be revised by the light of more 

 extended examination and research. 



In the present investigation, my attention has been 

 attracted more by the appearances suggestive of chemical 

 action producing changes in the sediments, than of altera- 

 tions brought about by dynamical metamorphism. The 

 effects observed are such as may, I think, be attributed in 

 part to mineral exudations from the plutonic magmas, as 

 also to the volatile emanations therefrom, such as i^^luorine 

 or Boron, which have evidently been strongly active at the 

 contacts, and under the exceptional conditions which must 

 have obtained there, have produced a recrystallisation 

 of the already regionally metamorphosed schists. Such 

 results were more marked in the district which I have 

 described in this paper, than those which could be attributed 

 to the compression and dislocation of rock masses subjected 

 to shearing strain. These latter phenomena can be studied 

 better in other parts of the Omeo district, and would properly 

 orm the subject of a separate memoir. 



The general conclusions to which the study of the 

 phenomena noted in this paper has led me may be briefly 

 stated as follows : — 



(1.) The contact referred to represents an extensive fault, 

 with a downthrow on the north-east side of undetermined 

 depth. 



(2.) The schists on the north-east side most probably 

 represent some of the regionally metamorphosed lower 

 palaeozoic sediments (Silurian). 



(3.) The schists were let down within the influence of 

 the plutonic magmas which invaded them, both horizontally 

 from the contact and from below upwards. 



(4.) The regional schists were probably phyllites and fine 

 grained mica schists, and by the further action of the 



K 



