GEOLOGY OF THE JENOLAN OAVES DISTRICT. 383 



of this rock. The sericite occurs largely along lines of flow, 

 and its appearance along certain planes as this would suggest 

 that it is an alteration product as the result of pressure. 

 The apparent flow structure might therefore be in part a 

 foliation due to dynamic action subsequent to consolidation. 

 The strain-shadowing sometimes noticed in the quartz 

 phenocrysts, with some fracturing, and the remarkably bent 

 felspar phenocrysts (slide x 52) may also have been due 

 to dynamic action, but these characteristics could have 

 been produced prior to consolidation, i.e., during flow. 



(4) Carbonates are more plentiful in this rock, the analysis 

 of which gives 6*01 per cent, of 00 2 . The calcification 

 etc. is due in large part to infiltration instead of the alter- 

 ation in situ of lime or magnesia bearing minerals. The 

 analysis indicates that there is not enough OaO present 

 (4*56%), to satisfy all the 00 2 to form calcite, therefore 

 some of the 0O 2 must be combined with the MgO, to 

 form magnesite or dolomite, with probably a little isomor- 

 phous ferrous carbonate. The presence of ferrous carbonate 

 is indicated by the separation of yellow oxide of iron from 

 the carbonate patches. 



Si0 2 ... 

 A1 2 3 

 Fe 2 3 

 FeO ... 

 MgO ... 

 OaO ... 

 Na 2 

 K ... 



Chemical Composition. 





Per cent. 





Per cent. 



63-22 



H 3 O(100° 



0.) 0-26 



13-57 



H 2 O(100° 



C. + ) 2-10 



1-50 



C0 2 ... 



6-01 



2-07 



Ti0 2 ... 



... 0-50 



1-80 



MnO ... 



... 0-09 



4-56 







0-98 





100-48 



3-82 







Note. — The rock and slide numbers quoted refer to registered 

 specimens and rock sections in the Sydney and Newcastle Technical 



College collections. 



