GEOLOGY AND PETROLOGY OF ENOGGERA GRANITE. 159 



Plate I. 

 VARIATION DIAGRAMS. 



These have been constructed by plotting the silica 

 percentage (on the horizontal axis) against the other oxides 

 in percentages (on the vertical axis). The scales are the 

 same for each axis and for each figure. 



Lines joining members of the Grey Phase are shown 



thus : 



Lines joining members of the Pink Phase are shown 



thus : 



Lines joining members of the New England Area are 

 shown thus: — | — j — | — | — j 



The position of the Enoggera Hydri'J is shown thus :© 

 The letter-numbers (E.l, S.3, N.4, &c.) refer to the 

 analyses of Tables III., IV., and V. 



Figure 1 shows the curves obtained by plotting K2O 

 and NaoO against SiO^. 



Figure 2 shows the curves obtained by plotting CaO 

 and ]\IgO against SiO,. 



Plates II. and III. 



MICROPHOTOGRAPHS. 



All the microphotographs are magnified 25 diameters. 

 No. 4, Plate II., was taken in ordinar.v light. All the other 

 microphotographs were taken with crossed nicols. 



Plate II. 



No. 1 (G.l) 141. — Pink Phase. Specimen from southern 



part of main Enoggera mass, X 25, crossed nicols. 



No. 2 (G.26) 422. — Pink Phase. Specimens from Green 

 Hill area, X 25, crossed nicols. 



No. 3 (G.43) 351. — ]Micrographie structure in Aplite, X 25, 

 crossed nicols. 



No. i (G.44) 416. — Grey Phase. ITornblendic type. Portion 

 374, parish of Enoggera, X 25, ordinary light. 



