42 



E. 0, Teale: 



(a). Normal Diabase. 



The diabasic rocks show some variation in character from a. 

 somewhat doleritic type to that of a dense basalt, the latter being" 

 the dominant type. The dense forms are almost identical in. 

 features with those^ of Heathcote. 



Though the sections at the Howqua do not show so clearly the 

 same interbedded succession, the character and occurrence of the- 

 diabase, and that of the associated cherts are so similar that the- 

 assumption is reasonable that here, too, they represent similar 

 submarine lavas, and tuffs, or interbedded cherts. 



Chemical Analysks of Diabases 



^^\ K. O. Teale 









Howqu.^ 





Heathcote 





No. 15 



No. 25 



No. 630 



SiO., 



- 





46. 4.4. 



58.17 



55.77 



A1.03 



- 





15.71 



13.15 



11.23 



Fe,03 



- 





.53 



3.18 



1.82 



FeO 



- 





11.21 



8.61 



10.11 



M-0 



. 





8.61 



0.91* 



7.94 



CaO 



- 





12.3 



6.7 



4.64 



Na^O 



- 





2.5 



7.00 



4.91 



K,0 



- 





.21 



0.41 



.73 



H.2O + 



. 





.21 



0.33 



.55 



H2O- 



. 



- 



2.54 



1.34 



1.91 



TiO, 







- 



0.8 



0.22 





100.46 



100.61 



99.80 



'■ Note low MffO content 



Mineral. 

 Quartz 

 Orthoclase - 

 Albite 

 Anorthite 



Diopside - 

 Hyperstliene 



Magnetite - 

 Ilmenite 



No. 25. — Soda, Rich Type. 

 Norm. % Group. 



.72 - - Q. 

 2.22 - 



- 59.21 - \ F. 64.45 



- 3.07 - 



28.0 

 3.56 



4.4 

 .15 



P. 31.56 



M. 4.55 



Salic. 65. ir 



Feinic 4.55 



