299 



to be virtually conformable. In some instances the 

 foliation is nearly north to south, which indicates that small 

 folds occur. The rocks have also yielded by fracturing, 

 shearing, and faulting. 



During and following the upper Jurassic orogenic period, 

 the Vancouver volcanics and Sutton limestones were 

 invaded by granitic rocks and their accompanying minor 

 intrusives, and at the contacts the volcanics were greatly 

 shattered, cut by apophyses, and, as mentioned, greatly 

 metamorphosed. The granitic rocks may be subdivided 

 into three main types, irrupted in a definite sequence as 

 follows: Wark gabbro-diorite gneiss; Colquitz quartz- 

 diorite gneiss; and Saanich granodiorite. The minor in- 

 trusives, most of which accompanied the irruptions of the 

 Saanich granodiorite, consist of dykes and small injected 

 bodies of diorite porphyrites. 



Batholithic and minor intrusives. 



The Wark and Colquitz gneisses form virtually a single 

 batholith, with a general northwest-southeast strike, cor- 

 responding with the strike of the Vancouver volcanics. 

 The Wark gneiss is a dark greenish rock of medium to 

 coarse grain and gneissic texture, consisting essentially of 

 light greenish weathering plagioclase (labradorite- 

 andesine) and hornblende, and since it is intermediate in 

 composition between a gabbro and a diorite is classed as a 

 gabbro-diorite. The following is an analysis of a typical 

 sample. 



Si0 2 



48-68 



AI0O3 



... 18-05 



FeoOs 



. . . . V4-I 



Fe 



. . . . 6-44 



Mg 



... 2-82 



Ca 



... 10-00 



NaoO 



VI8 



K 2 



... I • 60 



H 2 + 



... 2-40 



Ti 2 



... o-8o 



P 2 5 



... 2-01 



Mn 



0-20 







Specific gravity .... 



99-59 

 ... 2-91 



