GEOLOGY OF THE NORTH CREEK QUADRANGLE 



33 



Table 6 

 Mode of gabbro 



Plagioclase . . 

 Orthoclase . . 

 Hornblende . 

 Hypersthene 



Biotite 



Augite 



Garnet 



Ilmenite . . . . 



Pyrite 



Apatite 



Units 

 measured 



805 



335 

 990 



932 

 505 

 227 

 265 

 184 



95 

 26 



7 364 



Rel. vols. 



38.09 



4 55 



27.02 



12.65 



6.86 



3 08 



3 59 

 2.50 

 1 .29 



■35 



99.98 



S. G. 



2.66 

 2.56 

 3.20 



3 50 

 3.20 



3 30 

 3 70 



5 17 

 5.00 

 3.20 



Units by 

 weight 



Percentage 

 weights 



461 



32 



858 



3 



368 



27 



262 



14 



616 



7 



749 



3 



980 



4 



951 



4 



475 



2 



«3 





22 803 



72 



77 

 92 



30 

 09 

 29 

 30 

 17 

 08 



36 



100.00 



Under the old qualitative system the rock is a hornblende norite, 

 while according to the quantitative system it is a hornblende-camp- 

 tonose. In thin-section the plagioclase is seen to range from oligo- 

 clase to labradorite, and the analysis and mode show that the average 

 composition is that of a basic andesine. The high TiO^ of the an- 

 alysis shows either ilmenite or very titaniferous magnetite, the 

 ilmenite being far more probable because of the difficulty of other- 

 wise accounting for such a low content of Fe^Oa. 



